Merge pull request #22 from aeternity/gh3553-refactor-plugin-final

Refactor to support column families, direct rocksdb access

.gitignore

@@ -1,2 +1 @@
-/doc
 /_build

Makefile

@@ -1,7 +1,7 @@
 suite=$(if $(SUITE), suite=$(SUITE), )
 REBAR3=$(shell which rebar3 || echo ./rebar3)
 
-.PHONY: all check test clean run
+.PHONY: all check test clean run dialyzer xref
 
 all:
 	$(REBAR3) compile
@@ -18,7 +18,13 @@ eunit:
 ct:
 	$(REBAR3) ct $(suite)
 
-test: eunit ct
+test: dialyzer xref eunit ct
+
+dialyzer:
+	$(REBAR3) dialyzer
+
+xref:
+	$(REBAR3) xref
 
 conf_clean:
 	@:

README.md

@@ -1,16 +1,53 @@
-# mnesia_rocksdb
 
-A RocksDB backend for Mnesia.
 
-This permits Erlang/OTP applications to use RocksDB as a backend for
+# Mnesia Rocksdb - Rocksdb backend plugin for Mnesia #
-mnesia tables. It is based on Klarna's `mnesia_eleveldb`.
 
-## Prerequisites
+Copyright (c) 2013-21 Klarna AB
 
-- rocksdb (included as dependency)
+__Authors:__ Ulf Wiger ([`ulf@wiger.net`](mailto:ulf@wiger.net)).
-- Erlang/OTP 20.0 or newer (https://github.com/erlang/otp)
 
-## Getting started
+The Mnesia DBMS, part of Erlang/OTP, supports 'backend plugins', making
+it possible to utilize more capable key-value stores than the `dets`
+module (limited to 2 GB per table). Unfortunately, this support is
+undocumented. Below, some informal documentation for the plugin system
+is provided.
+
+
+### <a name="Table_of_Contents">Table of Contents</a> ###
+
+
+1. [Usage](https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/README.md#Usage)
+1. [Prerequisites](https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/README.md#Prerequisites)
+1. [Getting started](https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/README.md#Getting_started)
+1. [Special features](https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/README.md#Special_features)
+1. [Customization](https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/README.md#Customization)
+1. [Handling of errors in write operations](https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/README.md#Handling_of_errors_in_write_operations)
+1. [Caveats](https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/README.md#Caveats)
+
+1. [Mnesia backend plugins](https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/README.md#Mnesia_backend_plugins)
+1. [Background](https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/README.md#Background)
+1. [Design](https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/README.md#Design)
+
+1. [Mnesia index plugins](https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/README.md#Mnesia_index_plugins)
+
+1. [Rocksdb](https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/README.md#Rocksdb)
+
+
+
+### <a name="Usage">Usage</a> ###
+
+
+#### <a name="Prerequisites">Prerequisites</a> ####
+
+* rocksdb (included as dependency)
+
+* sext (included as dependency)
+
+* Erlang/OTP 21.0 or newer (https://github.com/erlang/otp)
+
+
+
+#### <a name="Getting_started">Getting started</a> ####
 
 Call `mnesia_rocksdb:register()` immediately after
 starting mnesia.
@@ -18,30 +55,32 @@ starting mnesia.
 Put `{rocksdb_copies, [node()]}` into the table definitions of
 tables you want to be in RocksDB.
 
-## Special features
 
-RocksDB tables support efficient selects on *prefix keys*.
+#### <a name="Special_features">Special features</a> ####
+
+RocksDB tables support efficient selects on _prefix keys_.
 
 The backend uses the `sext` module (see
-https://github.com/uwiger/sext) for mapping between Erlang terms and the
+[`https://github.com/uwiger/sext`](https://github.com/uwiger/sext)) for mapping between Erlang terms and the
 binary data stored in the tables. This provides two useful properties:
 
-- The records are stored in the Erlang term order of their keys.
+* The records are stored in the Erlang term order of their keys.
-- A prefix of a composite key is ordered just before any key for which
+
-  it is a prefix. For example, `{x, '_'}` is a prefix for keys `{x, a}`,
+* A prefix of a composite key is ordered just before any key for which
-  `{x, b}` and so on.
+  it is a prefix. For example, `{x, '_'}` is a prefix for keys `{x, a}`,`{x, b}` and so on.
+
 
 This means that a prefix key identifies the start of the sequence of
 entries whose keys match the prefix. The backend uses this to optimize
 selects on prefix keys.
 
-## Customization
+### Customization
 
 RocksDB supports a number of customization options. These can be specified
 by providing a `{Key, Value}` list named `rocksdb_opts` under `user_properties`,
 for example:
 
-```erlang
+```
 mnesia:create_table(foo, [{rocksdb_copies, [node()]},
                           ...
                           {user_properties,
@@ -53,6 +92,7 @@ Consult the [RocksDB documentation](https://github.com/facebook/rocksdb/wiki/Set
 for information on configuration parameters. Also see the section below on handling write errors.
 
 The default configuration for tables in `mnesia_rocksdb` is:
+
 ```
 default_open_opts() ->
     [ {create_if_missing, true}
@@ -74,60 +114,169 @@ This is experimental, and mostly copied from `mnesia_leveldb`. Consult the
 source code in `mnesia_rocksdb_tuning.erl` and `mnesia_rocksdb_params.erl`.
 Contributions are welcome.
 
-## Handling of errors in write operations
 
-The RocksDB update operations return either `ok` or `{error, any()}`.
+#### <a name="Caveats">Caveats</a> ####
-Since the actual updates are performed after the 'point-of-no-return',
-returning an `error` result will cause mnesia to behave unpredictably,
-since the operations are expected to simply work.
-
-### Option 1: `on_write_error`
-
-An `on_write_error` option can be provided, per-table, in the `rocksdb_opts`
-user property (see [Customization](#customization) above).
-Supported values indicate at which level an error indication should be reported.
-Mnesia may save reported events in RAM, and may also print them,
-depending on the debug level (controlled with `mnesia:set_debug_level/1`).
-
-Mnesia debug levels are, in increasing detail, `none | verbose | debug | trace`
-The supported values for `on_write_error` are:
-
- | Value   | Saved at debug level | Printed at debug level | Action    |
- | ------- | -------------------- | ---------------------- | --------- |
- | debug   | unless none          | verbose, debug, trace  | ignore    |
- | verbose | unless none          | verbose, debug, trace  | ignore    |
- | warning | always               | always                 | ignore    |
- | error   | always               | always                 | exception |
- | fatal   | always               | always                 | core dump |
-
-### Option 2: `on_write_error_store`
-
-An `on_write_error_store` option can be provided, per-table, in the `rocksdb_opts`
-user property (see [Customization](#customization) above).
-When set, the backend will use the value of the option as the name for an ETS table
-which is used as storage for runtime write errors. The table must be set up outside
-of the backend by the clients themselves.
-
-Entries to the table are in the form of a tuple `{{Table, Key}, Error, InsertedAt}`
-where `Table` refers to the Mnesia table name, `Key` is the primary key being used by Mnesia,
-`Error` is the error encountered by the backend, and `InsertedAt` refers to the time
-the error was encountered as system time in milliseconds.
-
-The backend will only insert entries and otherwise not manage the table. Thus, clients
-are expected to clean up the table during runtime to prevent memory leakage.
-
-## Caveats
 
 Avoid placing `bag` tables in RocksDB. Although they work, each write
 requires additional reads, causing substantial runtime overheads. There
 are better ways to represent and process bag data (see above about
-*prefix keys*).
+_prefix keys_).
 
 The `mnesia:table_info(T, size)` call always returns zero for RocksDB
 tables. RocksDB itself does not track the number of elements in a table, and
-although it is possible to make the mnesia_rocksdb backend maintain a size
+although it is possible to make the `mnesia_rocksdb` backend maintain a size
 counter, it incurs a high runtime overhead for writes and deletes since it
 forces them to first do a read to check the existence of the key. If you
 depend on having an up to date size count at all times, you need to maintain
 it yourself. If you only need the size occasionally, you may traverse the
 table to count the elements.
+
+
+### <a name="Mnesia_backend_plugins">Mnesia backend plugins</a> ###
+
+
+#### <a name="Background">Background</a> ####
+
+Mnesia was initially designed to be a RAM-only DBMS, and Erlang's
+`ets` tables were developed for this purpose. In order to support
+persistence, e.g. for configuration data, a disk-based version of `ets`
+(called `dets`) was created. The `dets` API mimicks the `ets` API,
+and `dets` is quite convenient and fast for (nowadays) small datasets.
+However, using a 32-bit bucket system, it is limited to 2GB of data.
+It also doesn't support ordered sets. When used in Mnesia, dets-based
+tables are called `disc_only_copies`.
+
+To circumvent these limitations, another table type, called `disc_copies`
+was added. This is a combination of `ets` and `disk_log`, where Mnesia
+periodically snapshots the `ets` data to a log file on disk, and meanwhile
+maintains a log of updates, which can be applied at startup. These tables
+are quite performant (especially on read access), but all data is kept in
+RAM, which can become a serious limitation.
+
+A backend plugin system was proposed by Ulf Wiger in 2016, and further
+developed with Klarna's support, to finally become included in OTP 19.
+Klarna uses a LevelDb backend, but Aeternity, in 2017, instead chose
+to implement a Rocksdb backend plugin.
+
+
+### <a name="Design">Design</a> ###
+
+As backend plugins were added on a long-since legacy-stable Mnesia,
+they had to conform to the existing code structure. For this reason,
+the plugin callbacks hook into the already present low-level access
+API in the `mnesia_lib` module. As a consequence, backend plugins have
+the same access semantics and granularity as `ets` and `dets`. This
+isn't much of a disadvantage for key-value stores like LevelDb and RocksDB,
+but a more serious issue is that the update part of this API is called
+on _after_ the point of no return. That is, Mnesia does not expect
+these updates to fail, and has no recourse if they do. As an aside,
+this could also happen if a `disc_only_copies` table exceeds the 2 GB
+limit (mnesia will not check it, and `dets` will not complain, but simply
+drop the update.)
+
+
+### <a name="Mnesia_index_plugins">Mnesia index plugins</a> ###
+
+When adding support for backend plugins, index plugins were also added. Unfortunately, they remain undocumented.
+
+An index plugin can be added in one of two ways:
+
+1. When creating a schema, provide `{index_plugins, [{Name, Module, Function}]}` options.
+
+1. Call the function `mnesia_schema:add_index_plugin(Name, Module, Function)`
+
+
+`Name` must be an atom wrapped as a 1-tuple, e.g. `{words}`.
+
+The plugin callback is called as `Module:Function(Table, Pos, Obj)`, where `Pos=={words}` in
+our example. It returns a list of index terms.
+
+<strong>Example</strong>
+
+Given the following index plugin implementation:
+
+```
+-module(words).
+-export([words_f/3]).
+
+words_f(_,_,Obj) when is_tuple(Obj) ->
+    words_(tuple_to_list(Obj)).
+
+words_(Str) when is_binary(Str) ->
+    string:lexemes(Str, [$\s, $\n, [$\r,$\n]]);
+words_(L) when is_list(L) ->
+    lists:flatmap(fun words_/1, L);
+words_(_) ->
+    [].
+```
+
+We can register the plugin and use it in table definitions:
+
+```
+Eshell V12.1.3  (abort with ^G)
+1> mnesia:start().
+ok
+2> mnesia_schema:add_index_plugin({words}, words, words_f).
+{atomic,ok}
+3> mnesia:create_table(i, [{index, [{words}]}]).
+{atomic,ok}
+```
+
+Note that in this case, we had neither a backend plugin, nor even a persistent schema.
+Index plugins can be used with all table types. The registered indexing function (arity 3) must exist
+as an exported function along the node's code path.
+
+To see what happens when we insert an object, we can turn on call trace.
+
+```
+4> dbg:tracer().
+{ok,<0.108.0>}
+5> dbg:tp(words, x).
+{ok,[{matched,nonode@nohost,3},{saved,x}]}
+6> dbg:p(all,[c]).
+{ok,[{matched,nonode@nohost,60}]}
+7> mnesia:dirty_write({i,<<"one two">>, [<<"three">>, <<"four">>]}).
+(<0.84.0>) call words:words_f(i,{words},{i,<<"one two">>,[<<"three">>,<<"four">>]})
+(<0.84.0>) returned from words:words_f/3 -> [<<"one">>,<<"two">>,<<"three">>,
+                                             <<"four">>]
+(<0.84.0>) call words:words_f(i,{words},{i,<<"one two">>,[<<"three">>,<<"four">>]})
+(<0.84.0>) returned from words:words_f/3 -> [<<"one">>,<<"two">>,<<"three">>,
+                                             <<"four">>]
+ok
+8> dbg:ctp('_'), dbg:stop().
+ok
+9> mnesia:dirty_index_read(i, <<"one">>, {words}).
+[{i,<<"one two">>,[<<"three">>,<<"four">>]}]
+```
+
+(The fact that the indexing function is called twice, seems like a performance bug.)
+
+We can observe that the indexing callback is able to operate on the whole object.
+It needs to be side-effect free and efficient, since it will be called at least once for each update
+(if an old object exists in the table, the indexing function will be called on it too, before it is
+replaced by the new object.)
+
+
+### <a name="Rocksdb">Rocksdb</a> ###
+
+
+### <a name="Usage">Usage</a> ###
+
+
+
+## Modules ##
+
+
+<table width="100%" border="0" summary="list of modules">
+<tr><td><a href="https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/mnesia_rocksdb.md" class="module">mnesia_rocksdb</a></td></tr>
+<tr><td><a href="https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/mnesia_rocksdb_admin.md" class="module">mnesia_rocksdb_admin</a></td></tr>
+<tr><td><a href="https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/mnesia_rocksdb_app.md" class="module">mnesia_rocksdb_app</a></td></tr>
+<tr><td><a href="https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/mnesia_rocksdb_lib.md" class="module">mnesia_rocksdb_lib</a></td></tr>
+<tr><td><a href="https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/mnesia_rocksdb_params.md" class="module">mnesia_rocksdb_params</a></td></tr>
+<tr><td><a href="https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/mnesia_rocksdb_sup.md" class="module">mnesia_rocksdb_sup</a></td></tr>
+<tr><td><a href="https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/mnesia_rocksdb_tuning.md" class="module">mnesia_rocksdb_tuning</a></td></tr>
+<tr><td><a href="https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/mrdb.md" class="module">mrdb</a></td></tr>
+<tr><td><a href="https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/mrdb_index.md" class="module">mrdb_index</a></td></tr>
+<tr><td><a href="https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/mrdb_mutex.md" class="module">mrdb_mutex</a></td></tr>
+<tr><td><a href="https://github.com/aeternity/mnesia_rocksdb/blob/g3553-refactor-plugin-migration-tmp-220318/doc/mrdb_select.md" class="module">mrdb_select</a></td></tr></table>
+

doc/README.md

@@ -0,0 +1,282 @@
+
+
+# Mnesia Rocksdb - Rocksdb backend plugin for Mnesia #
+
+Copyright (c) 2013-21 Klarna AB
+
+__Authors:__ Ulf Wiger ([`ulf@wiger.net`](mailto:ulf@wiger.net)).
+
+The Mnesia DBMS, part of Erlang/OTP, supports 'backend plugins', making
+it possible to utilize more capable key-value stores than the `dets`
+module (limited to 2 GB per table). Unfortunately, this support is
+undocumented. Below, some informal documentation for the plugin system
+is provided.
+
+
+### <a name="Table_of_Contents">Table of Contents</a> ###
+
+
+1. [Usage](#Usage)
+1. [Prerequisites](#Prerequisites)
+1. [Getting started](#Getting_started)
+1. [Special features](#Special_features)
+1. [Customization](#Customization)
+1. [Handling of errors in write operations](#Handling_of_errors_in_write_operations)
+1. [Caveats](#Caveats)
+
+1. [Mnesia backend plugins](#Mnesia_backend_plugins)
+1. [Background](#Background)
+1. [Design](#Design)
+
+1. [Mnesia index plugins](#Mnesia_index_plugins)
+
+1. [Rocksdb](#Rocksdb)
+
+
+
+### <a name="Usage">Usage</a> ###
+
+
+#### <a name="Prerequisites">Prerequisites</a> ####
+
+* rocksdb (included as dependency)
+
+* sext (included as dependency)
+
+* Erlang/OTP 21.0 or newer (https://github.com/erlang/otp)
+
+
+
+#### <a name="Getting_started">Getting started</a> ####
+
+Call `mnesia_rocksdb:register()` immediately after
+starting mnesia.
+
+Put `{rocksdb_copies, [node()]}` into the table definitions of
+tables you want to be in RocksDB.
+
+
+#### <a name="Special_features">Special features</a> ####
+
+RocksDB tables support efficient selects on _prefix keys_.
+
+The backend uses the `sext` module (see
+[`https://github.com/uwiger/sext`](https://github.com/uwiger/sext)) for mapping between Erlang terms and the
+binary data stored in the tables. This provides two useful properties:
+
+* The records are stored in the Erlang term order of their keys.
+
+* A prefix of a composite key is ordered just before any key for which
+  it is a prefix. For example, `{x, '_'}` is a prefix for keys `{x, a}`,`{x, b}` and so on.
+
+
+This means that a prefix key identifies the start of the sequence of
+entries whose keys match the prefix. The backend uses this to optimize
+selects on prefix keys.
+
+### Customization
+
+RocksDB supports a number of customization options. These can be specified
+by providing a `{Key, Value}` list named `rocksdb_opts` under `user_properties`,
+for example:
+
+```
+mnesia:create_table(foo, [{rocksdb_copies, [node()]},
+                          ...
+                          {user_properties,
+                              [{rocksdb_opts, [{max_open_files, 1024}]}]
+                          }])
+```
+
+Consult the [RocksDB documentation](https://github.com/facebook/rocksdb/wiki/Setup-Options-and-Basic-Tuning)
+for information on configuration parameters. Also see the section below on handling write errors.
+
+The default configuration for tables in `mnesia_rocksdb` is:
+
+```
+default_open_opts() ->
+    [ {create_if_missing, true}
+      , {cache_size,
+         list_to_integer(get_env_default("ROCKSDB_CACHE_SIZE", "32212254"))}
+      , {block_size, 1024}
+      , {max_open_files, 100}
+      , {write_buffer_size,
+         list_to_integer(get_env_default(
+                           "ROCKSDB_WRITE_BUFFER_SIZE", "4194304"))}
+      , {compression,
+         list_to_atom(get_env_default("ROCKSDB_COMPRESSION", "true"))}
+      , {use_bloomfilter, true}
+    ].
+```
+
+It is also possible, for larger databases, to produce a tuning parameter file.
+This is experimental, and mostly copied from `mnesia_leveldb`. Consult the
+source code in `mnesia_rocksdb_tuning.erl` and `mnesia_rocksdb_params.erl`.
+Contributions are welcome.
+
+
+#### <a name="Caveats">Caveats</a> ####
+
+Avoid placing `bag` tables in RocksDB. Although they work, each write
+requires additional reads, causing substantial runtime overheads. There
+are better ways to represent and process bag data (see above about
+_prefix keys_).
+
+The `mnesia:table_info(T, size)` call always returns zero for RocksDB
+tables. RocksDB itself does not track the number of elements in a table, and
+although it is possible to make the `mnesia_rocksdb` backend maintain a size
+counter, it incurs a high runtime overhead for writes and deletes since it
+forces them to first do a read to check the existence of the key. If you
+depend on having an up to date size count at all times, you need to maintain
+it yourself. If you only need the size occasionally, you may traverse the
+table to count the elements.
+
+
+### <a name="Mnesia_backend_plugins">Mnesia backend plugins</a> ###
+
+
+#### <a name="Background">Background</a> ####
+
+Mnesia was initially designed to be a RAM-only DBMS, and Erlang's
+`ets` tables were developed for this purpose. In order to support
+persistence, e.g. for configuration data, a disk-based version of `ets`
+(called `dets`) was created. The `dets` API mimicks the `ets` API,
+and `dets` is quite convenient and fast for (nowadays) small datasets.
+However, using a 32-bit bucket system, it is limited to 2GB of data.
+It also doesn't support ordered sets. When used in Mnesia, dets-based
+tables are called `disc_only_copies`.
+
+To circumvent these limitations, another table type, called `disc_copies`
+was added. This is a combination of `ets` and `disk_log`, where Mnesia
+periodically snapshots the `ets` data to a log file on disk, and meanwhile
+maintains a log of updates, which can be applied at startup. These tables
+are quite performant (especially on read access), but all data is kept in
+RAM, which can become a serious limitation.
+
+A backend plugin system was proposed by Ulf Wiger in 2016, and further
+developed with Klarna's support, to finally become included in OTP 19.
+Klarna uses a LevelDb backend, but Aeternity, in 2017, instead chose
+to implement a Rocksdb backend plugin.
+
+
+### <a name="Design">Design</a> ###
+
+As backend plugins were added on a long-since legacy-stable Mnesia,
+they had to conform to the existing code structure. For this reason,
+the plugin callbacks hook into the already present low-level access
+API in the `mnesia_lib` module. As a consequence, backend plugins have
+the same access semantics and granularity as `ets` and `dets`. This
+isn't much of a disadvantage for key-value stores like LevelDb and RocksDB,
+but a more serious issue is that the update part of this API is called
+on _after_ the point of no return. That is, Mnesia does not expect
+these updates to fail, and has no recourse if they do. As an aside,
+this could also happen if a `disc_only_copies` table exceeds the 2 GB
+limit (mnesia will not check it, and `dets` will not complain, but simply
+drop the update.)
+
+
+### <a name="Mnesia_index_plugins">Mnesia index plugins</a> ###
+
+When adding support for backend plugins, index plugins were also added. Unfortunately, they remain undocumented.
+
+An index plugin can be added in one of two ways:
+
+1. When creating a schema, provide `{index_plugins, [{Name, Module, Function}]}` options.
+
+1. Call the function `mnesia_schema:add_index_plugin(Name, Module, Function)`
+
+
+`Name` must be an atom wrapped as a 1-tuple, e.g. `{words}`.
+
+The plugin callback is called as `Module:Function(Table, Pos, Obj)`, where `Pos=={words}` in
+our example. It returns a list of index terms.
+
+<strong>Example</strong>
+
+Given the following index plugin implementation:
+
+```
+-module(words).
+-export([words_f/3]).
+
+words_f(_,_,Obj) when is_tuple(Obj) ->
+    words_(tuple_to_list(Obj)).
+
+words_(Str) when is_binary(Str) ->
+    string:lexemes(Str, [$\s, $\n, [$\r,$\n]]);
+words_(L) when is_list(L) ->
+    lists:flatmap(fun words_/1, L);
+words_(_) ->
+    [].
+```
+
+We can register the plugin and use it in table definitions:
+
+```
+Eshell V12.1.3  (abort with ^G)
+1> mnesia:start().
+ok
+2> mnesia_schema:add_index_plugin({words}, words, words_f).
+{atomic,ok}
+3> mnesia:create_table(i, [{index, [{words}]}]).
+{atomic,ok}
+```
+
+Note that in this case, we had neither a backend plugin, nor even a persistent schema.
+Index plugins can be used with all table types. The registered indexing function (arity 3) must exist
+as an exported function along the node's code path.
+
+To see what happens when we insert an object, we can turn on call trace.
+
+```
+4> dbg:tracer().
+{ok,<0.108.0>}
+5> dbg:tp(words, x).
+{ok,[{matched,nonode@nohost,3},{saved,x}]}
+6> dbg:p(all,[c]).
+{ok,[{matched,nonode@nohost,60}]}
+7> mnesia:dirty_write({i,<<"one two">>, [<<"three">>, <<"four">>]}).
+(<0.84.0>) call words:words_f(i,{words},{i,<<"one two">>,[<<"three">>,<<"four">>]})
+(<0.84.0>) returned from words:words_f/3 -> [<<"one">>,<<"two">>,<<"three">>,
+                                             <<"four">>]
+(<0.84.0>) call words:words_f(i,{words},{i,<<"one two">>,[<<"three">>,<<"four">>]})
+(<0.84.0>) returned from words:words_f/3 -> [<<"one">>,<<"two">>,<<"three">>,
+                                             <<"four">>]
+ok
+8> dbg:ctp('_'), dbg:stop().
+ok
+9> mnesia:dirty_index_read(i, <<"one">>, {words}).
+[{i,<<"one two">>,[<<"three">>,<<"four">>]}]
+```
+
+(The fact that the indexing function is called twice, seems like a performance bug.)
+
+We can observe that the indexing callback is able to operate on the whole object.
+It needs to be side-effect free and efficient, since it will be called at least once for each update
+(if an old object exists in the table, the indexing function will be called on it too, before it is
+replaced by the new object.)
+
+
+### <a name="Rocksdb">Rocksdb</a> ###
+
+
+### <a name="Usage">Usage</a> ###
+
+
+
+## Modules ##
+
+
+<table width="100%" border="0" summary="list of modules">
+<tr><td><a href="mnesia_rocksdb.md" class="module">mnesia_rocksdb</a></td></tr>
+<tr><td><a href="mnesia_rocksdb_admin.md" class="module">mnesia_rocksdb_admin</a></td></tr>
+<tr><td><a href="mnesia_rocksdb_app.md" class="module">mnesia_rocksdb_app</a></td></tr>
+<tr><td><a href="mnesia_rocksdb_lib.md" class="module">mnesia_rocksdb_lib</a></td></tr>
+<tr><td><a href="mnesia_rocksdb_params.md" class="module">mnesia_rocksdb_params</a></td></tr>
+<tr><td><a href="mnesia_rocksdb_sup.md" class="module">mnesia_rocksdb_sup</a></td></tr>
+<tr><td><a href="mnesia_rocksdb_tuning.md" class="module">mnesia_rocksdb_tuning</a></td></tr>
+<tr><td><a href="mrdb.md" class="module">mrdb</a></td></tr>
+<tr><td><a href="mrdb_index.md" class="module">mrdb_index</a></td></tr>
+<tr><td><a href="mrdb_mutex.md" class="module">mrdb_mutex</a></td></tr>
+<tr><td><a href="mrdb_select.md" class="module">mrdb_select</a></td></tr></table>
+

doc/edoc-info

@@ -0,0 +1,5 @@
+%% encoding: UTF-8
+{application,mnesia_rocksdb}.
+{modules,[mnesia_rocksdb,mnesia_rocksdb_admin,mnesia_rocksdb_app,
+          mnesia_rocksdb_lib,mnesia_rocksdb_params,mnesia_rocksdb_sup,
+          mnesia_rocksdb_tuning,mrdb,mrdb_index,mrdb_mutex,mrdb_select]}.

doc/mnesia_rocksdb_admin.md

@@ -0,0 +1,326 @@
+
+
+# Module mnesia_rocksdb_admin #
+* [Data Types](#types)
+* [Function Index](#index)
+* [Function Details](#functions)
+
+__Behaviours:__ [`gen_server`](gen_server.md).
+
+<a name="types"></a>
+
+## Data Types ##
+
+
+
+
+### <a name="type-alias">alias()</a> ###
+
+
+<pre><code>
+alias() = atom()
+</code></pre>
+
+
+
+
+### <a name="type-backend">backend()</a> ###
+
+
+<pre><code>
+backend() = #{db_ref =&gt; <a href="#type-db_ref">db_ref()</a>, cf_info =&gt; #{<a href="#type-table">table()</a> =&gt; <a href="#type-cf">cf()</a>}}
+</code></pre>
+
+
+
+
+### <a name="type-cf">cf()</a> ###
+
+
+<pre><code>
+cf() = <a href="http://www.erlang.org/doc/man/mrdb.html#type-db_ref">mrdb:db_ref()</a>
+</code></pre>
+
+
+
+
+### <a name="type-db_ref">db_ref()</a> ###
+
+
+<pre><code>
+db_ref() = <a href="/home/uwiger/ae/mnesia_rocksdb/_build/default/lib/rocksdb/doc/rocksdb.md#type-db_handle">rocksdb:db_handle()</a>
+</code></pre>
+
+
+
+
+### <a name="type-gen_server_noreply">gen_server_noreply()</a> ###
+
+
+<pre><code>
+gen_server_noreply() = {noreply, <a href="#type-st">st()</a>} | {stop, <a href="#type-reason">reason()</a>, <a href="#type-st">st()</a>}
+</code></pre>
+
+
+
+
+### <a name="type-gen_server_reply">gen_server_reply()</a> ###
+
+
+<pre><code>
+gen_server_reply() = {reply, <a href="#type-reply">reply()</a>, <a href="#type-st">st()</a>} | {stop, <a href="#type-reason">reason()</a>, <a href="#type-reply">reply()</a>, <a href="#type-st">st()</a>}
+</code></pre>
+
+
+
+
+### <a name="type-properties">properties()</a> ###
+
+
+<pre><code>
+properties() = [{atom(), any()}]
+</code></pre>
+
+
+
+
+### <a name="type-reason">reason()</a> ###
+
+
+<pre><code>
+reason() = any()
+</code></pre>
+
+
+
+
+### <a name="type-reply">reply()</a> ###
+
+
+<pre><code>
+reply() = any()
+</code></pre>
+
+
+
+
+### <a name="type-req">req()</a> ###
+
+
+<pre><code>
+req() = {create_table, <a href="#type-table">table()</a>, <a href="#type-properties">properties()</a>} | {delete_table, <a href="#type-table">table()</a>} | {load_table, <a href="#type-table">table()</a>} | {related_resources, <a href="#type-table">table()</a>} | {get_ref, <a href="#type-table">table()</a>} | {add_aliases, [<a href="#type-alias">alias()</a>]} | {write_table_property, <a href="#type-tabname">tabname()</a>, tuple()} | {remove_aliases, [<a href="#type-alias">alias()</a>]} | {migrate, [{<a href="#type-tabname">tabname()</a>, map()}]} | {prep_close, <a href="#type-table">table()</a>} | {close_table, <a href="#type-table">table()</a>}
+</code></pre>
+
+
+
+
+### <a name="type-st">st()</a> ###
+
+
+<pre><code>
+st() = #st{backends = #{<a href="#type-alias">alias()</a> =&gt; <a href="#type-backend">backend()</a>}, standalone = #{{<a href="#type-alias">alias()</a>, <a href="#type-table">table()</a>} =&gt; <a href="#type-cf">cf()</a>}, default_opts = [{atom(), term()}]}
+</code></pre>
+
+
+
+
+### <a name="type-table">table()</a> ###
+
+
+<pre><code>
+table() = <a href="#type-tabname">tabname()</a> | {admin, <a href="#type-alias">alias()</a>} | {<a href="#type-tabname">tabname()</a>, index, any()} | {<a href="#type-tabname">tabname()</a>, retainer, any()}
+</code></pre>
+
+
+
+
+### <a name="type-tabname">tabname()</a> ###
+
+
+<pre><code>
+tabname() = atom()
+</code></pre>
+
+<a name="index"></a>
+
+## Function Index ##
+
+
+<table width="100%" border="1" cellspacing="0" cellpadding="2" summary="function index"><tr><td valign="top"><a href="#add_aliases-1">add_aliases/1</a></td><td></td></tr><tr><td valign="top"><a href="#close_table-2">close_table/2</a></td><td></td></tr><tr><td valign="top"><a href="#code_change-3">code_change/3</a></td><td></td></tr><tr><td valign="top"><a href="#create_table-3">create_table/3</a></td><td></td></tr><tr><td valign="top"><a href="#delete_table-2">delete_table/2</a></td><td></td></tr><tr><td valign="top"><a href="#ensure_started-0">ensure_started/0</a></td><td></td></tr><tr><td valign="top"><a href="#get_ref-1">get_ref/1</a></td><td></td></tr><tr><td valign="top"><a href="#get_ref-2">get_ref/2</a></td><td></td></tr><tr><td valign="top"><a href="#handle_call-3">handle_call/3</a></td><td></td></tr><tr><td valign="top"><a href="#handle_cast-2">handle_cast/2</a></td><td></td></tr><tr><td valign="top"><a href="#handle_info-2">handle_info/2</a></td><td></td></tr><tr><td valign="top"><a href="#init-1">init/1</a></td><td></td></tr><tr><td valign="top"><a href="#load_table-2">load_table/2</a></td><td></td></tr><tr><td valign="top"><a href="#meta-0">meta/0</a></td><td></td></tr><tr><td valign="top"><a href="#migrate_standalone-2">migrate_standalone/2</a></td><td></td></tr><tr><td valign="top"><a href="#prep_close-2">prep_close/2</a></td><td></td></tr><tr><td valign="top"><a href="#read_info-1">read_info/1</a></td><td></td></tr><tr><td valign="top"><a href="#read_info-2">read_info/2</a></td><td></td></tr><tr><td valign="top"><a href="#read_info-4">read_info/4</a></td><td></td></tr><tr><td valign="top"><a href="#related_resources-2">related_resources/2</a></td><td></td></tr><tr><td valign="top"><a href="#remove_aliases-1">remove_aliases/1</a></td><td></td></tr><tr><td valign="top"><a href="#request_ref-2">request_ref/2</a></td><td></td></tr><tr><td valign="top"><a href="#start_link-0">start_link/0</a></td><td></td></tr><tr><td valign="top"><a href="#terminate-2">terminate/2</a></td><td></td></tr><tr><td valign="top"><a href="#write_info-4">write_info/4</a></td><td></td></tr><tr><td valign="top"><a href="#write_table_property-3">write_table_property/3</a></td><td></td></tr></table>
+
+
+<a name="functions"></a>
+
+## Function Details ##
+
+<a name="add_aliases-1"></a>
+
+### add_aliases/1 ###
+
+`add_aliases(Aliases) -> any()`
+
+<a name="close_table-2"></a>
+
+### close_table/2 ###
+
+`close_table(Alias, Name) -> any()`
+
+<a name="code_change-3"></a>
+
+### code_change/3 ###
+
+`code_change(FromVsn, St, Extra) -> any()`
+
+<a name="create_table-3"></a>
+
+### create_table/3 ###
+
+`create_table(Alias, Name, Props) -> any()`
+
+<a name="delete_table-2"></a>
+
+### delete_table/2 ###
+
+<pre><code>
+delete_table(Alias::<a href="#type-alias">alias()</a>, Name::<a href="#type-tabname">tabname()</a>) -&gt; ok
+</code></pre>
+<br />
+
+<a name="ensure_started-0"></a>
+
+### ensure_started/0 ###
+
+<pre><code>
+ensure_started() -&gt; ok
+</code></pre>
+<br />
+
+<a name="get_ref-1"></a>
+
+### get_ref/1 ###
+
+`get_ref(Name) -> any()`
+
+<a name="get_ref-2"></a>
+
+### get_ref/2 ###
+
+`get_ref(Name, Default) -> any()`
+
+<a name="handle_call-3"></a>
+
+### handle_call/3 ###
+
+<pre><code>
+handle_call(Req::{<a href="#type-alias">alias()</a>, <a href="#type-req">req()</a>}, From::any(), St::<a href="#type-st">st()</a>) -&gt; <a href="#type-gen_server_reply">gen_server_reply()</a>
+</code></pre>
+<br />
+
+<a name="handle_cast-2"></a>
+
+### handle_cast/2 ###
+
+<pre><code>
+handle_cast(Msg::any(), St::<a href="#type-st">st()</a>) -&gt; <a href="#type-gen_server_noreply">gen_server_noreply()</a>
+</code></pre>
+<br />
+
+<a name="handle_info-2"></a>
+
+### handle_info/2 ###
+
+<pre><code>
+handle_info(Msg::any(), St::<a href="#type-st">st()</a>) -&gt; <a href="#type-gen_server_noreply">gen_server_noreply()</a>
+</code></pre>
+<br />
+
+<a name="init-1"></a>
+
+### init/1 ###
+
+`init(X1) -> any()`
+
+<a name="load_table-2"></a>
+
+### load_table/2 ###
+
+`load_table(Alias, Name) -> any()`
+
+<a name="meta-0"></a>
+
+### meta/0 ###
+
+`meta() -> any()`
+
+<a name="migrate_standalone-2"></a>
+
+### migrate_standalone/2 ###
+
+`migrate_standalone(Alias, Tabs) -> any()`
+
+<a name="prep_close-2"></a>
+
+### prep_close/2 ###
+
+`prep_close(Alias, Tab) -> any()`
+
+<a name="read_info-1"></a>
+
+### read_info/1 ###
+
+`read_info(TRec) -> any()`
+
+<a name="read_info-2"></a>
+
+### read_info/2 ###
+
+`read_info(Alias, Tab) -> any()`
+
+<a name="read_info-4"></a>
+
+### read_info/4 ###
+
+`read_info(Alias, Tab, K, Default) -> any()`
+
+<a name="related_resources-2"></a>
+
+### related_resources/2 ###
+
+`related_resources(Alias, Name) -> any()`
+
+<a name="remove_aliases-1"></a>
+
+### remove_aliases/1 ###
+
+`remove_aliases(Aliases) -> any()`
+
+<a name="request_ref-2"></a>
+
+### request_ref/2 ###
+
+`request_ref(Alias, Name) -> any()`
+
+<a name="start_link-0"></a>
+
+### start_link/0 ###
+
+`start_link() -> any()`
+
+<a name="terminate-2"></a>
+
+### terminate/2 ###
+
+`terminate(X1, St) -> any()`
+
+<a name="write_info-4"></a>
+
+### write_info/4 ###
+
+`write_info(Alias, Tab, K, V) -> any()`
+
+<a name="write_table_property-3"></a>
+
+### write_table_property/3 ###
+
+`write_table_property(Alias, Tab, Prop) -> any()`
+

doc/mnesia_rocksdb_app.md

@@ -0,0 +1,32 @@
+
+
+# Module mnesia_rocksdb_app #
+* [Function Index](#index)
+* [Function Details](#functions)
+
+__Behaviours:__ [`application`](application.md).
+
+<a name="index"></a>
+
+## Function Index ##
+
+
+<table width="100%" border="1" cellspacing="0" cellpadding="2" summary="function index"><tr><td valign="top"><a href="#start-2">start/2</a></td><td></td></tr><tr><td valign="top"><a href="#stop-1">stop/1</a></td><td></td></tr></table>
+
+
+<a name="functions"></a>
+
+## Function Details ##
+
+<a name="start-2"></a>
+
+### start/2 ###
+
+`start(StartType, StartArgs) -> any()`
+
+<a name="stop-1"></a>
+
+### stop/1 ###
+
+`stop(State) -> any()`
+

doc/mnesia_rocksdb_lib.md

@@ -0,0 +1,168 @@
+
+
+# Module mnesia_rocksdb_lib #
+* [Description](#description)
+* [Function Index](#index)
+* [Function Details](#functions)
+
+RocksDB update wrappers, in separate module for easy tracing and mocking.
+
+<a name="description"></a>
+
+## Description ##
+<a name="index"></a>
+
+## Function Index ##
+
+
+<table width="100%" border="1" cellspacing="0" cellpadding="2" summary="function index"><tr><td valign="top"><a href="#check_encoding-2">check_encoding/2</a></td><td></td></tr><tr><td valign="top"><a href="#create_mountpoint-1">create_mountpoint/1</a></td><td></td></tr><tr><td valign="top"><a href="#data_mountpoint-1">data_mountpoint/1</a></td><td></td></tr><tr><td valign="top"><a href="#decode-2">decode/2</a></td><td></td></tr><tr><td valign="top"><a href="#decode_key-1">decode_key/1</a></td><td></td></tr><tr><td valign="top"><a href="#decode_key-2">decode_key/2</a></td><td></td></tr><tr><td valign="top"><a href="#decode_val-1">decode_val/1</a></td><td></td></tr><tr><td valign="top"><a href="#decode_val-3">decode_val/3</a></td><td></td></tr><tr><td valign="top"><a href="#default_encoding-3">default_encoding/3</a></td><td></td></tr><tr><td valign="top"><a href="#delete-3">delete/3</a></td><td></td></tr><tr><td valign="top"><a href="#encode-2">encode/2</a></td><td></td></tr><tr><td valign="top"><a href="#encode_key-1">encode_key/1</a></td><td></td></tr><tr><td valign="top"><a href="#encode_key-2">encode_key/2</a></td><td></td></tr><tr><td valign="top"><a href="#encode_val-1">encode_val/1</a></td><td></td></tr><tr><td valign="top"><a href="#encode_val-2">encode_val/2</a></td><td></td></tr><tr><td valign="top"><a href="#keypos-1">keypos/1</a></td><td></td></tr><tr><td valign="top"><a href="#open_rocksdb-3">open_rocksdb/3</a></td><td></td></tr><tr><td valign="top"><a href="#put-4">put/4</a></td><td></td></tr><tr><td valign="top"><a href="#tabname-1">tabname/1</a></td><td></td></tr><tr><td valign="top"><a href="#valid_key_type-2">valid_key_type/2</a></td><td></td></tr><tr><td valign="top"><a href="#valid_obj_type-2">valid_obj_type/2</a></td><td></td></tr><tr><td valign="top"><a href="#write-3">write/3</a></td><td></td></tr></table>
+
+
+<a name="functions"></a>
+
+## Function Details ##
+
+<a name="check_encoding-2"></a>
+
+### check_encoding/2 ###
+
+`check_encoding(Encoding, Attributes) -> any()`
+
+<a name="create_mountpoint-1"></a>
+
+### create_mountpoint/1 ###
+
+`create_mountpoint(Tab) -> any()`
+
+<a name="data_mountpoint-1"></a>
+
+### data_mountpoint/1 ###
+
+`data_mountpoint(Tab) -> any()`
+
+<a name="decode-2"></a>
+
+### decode/2 ###
+
+`decode(Val, X2) -> any()`
+
+<a name="decode_key-1"></a>
+
+### decode_key/1 ###
+
+<pre><code>
+decode_key(CodedKey::binary()) -&gt; any()
+</code></pre>
+<br />
+
+<a name="decode_key-2"></a>
+
+### decode_key/2 ###
+
+`decode_key(CodedKey, Enc) -> any()`
+
+<a name="decode_val-1"></a>
+
+### decode_val/1 ###
+
+<pre><code>
+decode_val(CodedVal::binary()) -&gt; any()
+</code></pre>
+<br />
+
+<a name="decode_val-3"></a>
+
+### decode_val/3 ###
+
+`decode_val(CodedVal, K, Ref) -> any()`
+
+<a name="default_encoding-3"></a>
+
+### default_encoding/3 ###
+
+`default_encoding(X1, Type, As) -> any()`
+
+<a name="delete-3"></a>
+
+### delete/3 ###
+
+`delete(Ref, K, Opts) -> any()`
+
+<a name="encode-2"></a>
+
+### encode/2 ###
+
+`encode(Value, X2) -> any()`
+
+<a name="encode_key-1"></a>
+
+### encode_key/1 ###
+
+<pre><code>
+encode_key(Key::any()) -&gt; binary()
+</code></pre>
+<br />
+
+<a name="encode_key-2"></a>
+
+### encode_key/2 ###
+
+`encode_key(Key, X2) -> any()`
+
+<a name="encode_val-1"></a>
+
+### encode_val/1 ###
+
+<pre><code>
+encode_val(Val::any()) -&gt; binary()
+</code></pre>
+<br />
+
+<a name="encode_val-2"></a>
+
+### encode_val/2 ###
+
+`encode_val(Val, Enc) -> any()`
+
+<a name="keypos-1"></a>
+
+### keypos/1 ###
+
+`keypos(Tab) -> any()`
+
+<a name="open_rocksdb-3"></a>
+
+### open_rocksdb/3 ###
+
+`open_rocksdb(MPd, RdbOpts, CFs) -> any()`
+
+<a name="put-4"></a>
+
+### put/4 ###
+
+`put(Ref, K, V, Opts) -> any()`
+
+<a name="tabname-1"></a>
+
+### tabname/1 ###
+
+`tabname(Tab) -> any()`
+
+<a name="valid_key_type-2"></a>
+
+### valid_key_type/2 ###
+
+`valid_key_type(X1, Key) -> any()`
+
+<a name="valid_obj_type-2"></a>
+
+### valid_obj_type/2 ###
+
+`valid_obj_type(X1, Obj) -> any()`
+
+<a name="write-3"></a>
+
+### write/3 ###
+
+`write(X1, L, Opts) -> any()`
+

doc/mnesia_rocksdb_params.md

@@ -0,0 +1,80 @@
+
+
+# Module mnesia_rocksdb_params #
+* [Function Index](#index)
+* [Function Details](#functions)
+
+__Behaviours:__ [`gen_server`](gen_server.md).
+
+<a name="index"></a>
+
+## Function Index ##
+
+
+<table width="100%" border="1" cellspacing="0" cellpadding="2" summary="function index"><tr><td valign="top"><a href="#code_change-3">code_change/3</a></td><td></td></tr><tr><td valign="top"><a href="#delete-1">delete/1</a></td><td></td></tr><tr><td valign="top"><a href="#handle_call-3">handle_call/3</a></td><td></td></tr><tr><td valign="top"><a href="#handle_cast-2">handle_cast/2</a></td><td></td></tr><tr><td valign="top"><a href="#handle_info-2">handle_info/2</a></td><td></td></tr><tr><td valign="top"><a href="#init-1">init/1</a></td><td></td></tr><tr><td valign="top"><a href="#lookup-2">lookup/2</a></td><td></td></tr><tr><td valign="top"><a href="#start_link-0">start_link/0</a></td><td></td></tr><tr><td valign="top"><a href="#store-2">store/2</a></td><td></td></tr><tr><td valign="top"><a href="#terminate-2">terminate/2</a></td><td></td></tr></table>
+
+
+<a name="functions"></a>
+
+## Function Details ##
+
+<a name="code_change-3"></a>
+
+### code_change/3 ###
+
+`code_change(X1, S, X3) -> any()`
+
+<a name="delete-1"></a>
+
+### delete/1 ###
+
+`delete(Tab) -> any()`
+
+<a name="handle_call-3"></a>
+
+### handle_call/3 ###
+
+`handle_call(X1, X2, S) -> any()`
+
+<a name="handle_cast-2"></a>
+
+### handle_cast/2 ###
+
+`handle_cast(X1, S) -> any()`
+
+<a name="handle_info-2"></a>
+
+### handle_info/2 ###
+
+`handle_info(X1, S) -> any()`
+
+<a name="init-1"></a>
+
+### init/1 ###
+
+`init(X1) -> any()`
+
+<a name="lookup-2"></a>
+
+### lookup/2 ###
+
+`lookup(Tab, Default) -> any()`
+
+<a name="start_link-0"></a>
+
+### start_link/0 ###
+
+`start_link() -> any()`
+
+<a name="store-2"></a>
+
+### store/2 ###
+
+`store(Tab, Params) -> any()`
+
+<a name="terminate-2"></a>
+
+### terminate/2 ###
+
+`terminate(X1, X2) -> any()`
+

doc/mnesia_rocksdb_sup.md

@@ -0,0 +1,32 @@
+
+
+# Module mnesia_rocksdb_sup #
+* [Function Index](#index)
+* [Function Details](#functions)
+
+__Behaviours:__ [`supervisor`](supervisor.md).
+
+<a name="index"></a>
+
+## Function Index ##
+
+
+<table width="100%" border="1" cellspacing="0" cellpadding="2" summary="function index"><tr><td valign="top"><a href="#init-1">init/1</a></td><td></td></tr><tr><td valign="top"><a href="#start_link-0">start_link/0</a></td><td></td></tr></table>
+
+
+<a name="functions"></a>
+
+## Function Details ##
+
+<a name="init-1"></a>
+
+### init/1 ###
+
+`init(X1) -> any()`
+
+<a name="start_link-0"></a>
+
+### start_link/0 ###
+
+`start_link() -> any()`
+

doc/mnesia_rocksdb_tuning.md

@@ -0,0 +1,126 @@
+
+
+# Module mnesia_rocksdb_tuning #
+* [Function Index](#index)
+* [Function Details](#functions)
+
+<a name="index"></a>
+
+## Function Index ##
+
+
+<table width="100%" border="1" cellspacing="0" cellpadding="2" summary="function index"><tr><td valign="top"><a href="#cache-1">cache/1</a></td><td></td></tr><tr><td valign="top"><a href="#calc_sizes-0">calc_sizes/0</a></td><td></td></tr><tr><td valign="top"><a href="#calc_sizes-1">calc_sizes/1</a></td><td></td></tr><tr><td valign="top"><a href="#count_rdb_tabs-0">count_rdb_tabs/0</a></td><td></td></tr><tr><td valign="top"><a href="#count_rdb_tabs-1">count_rdb_tabs/1</a></td><td></td></tr><tr><td valign="top"><a href="#default-1">default/1</a></td><td></td></tr><tr><td valign="top"><a href="#describe_env-0">describe_env/0</a></td><td></td></tr><tr><td valign="top"><a href="#get_avail_ram-0">get_avail_ram/0</a></td><td></td></tr><tr><td valign="top"><a href="#get_maxfiles-0">get_maxfiles/0</a></td><td></td></tr><tr><td valign="top"><a href="#get_maxfiles-1">get_maxfiles/1</a></td><td></td></tr><tr><td valign="top"><a href="#ideal_max_files-0">ideal_max_files/0</a></td><td></td></tr><tr><td valign="top"><a href="#ideal_max_files-1">ideal_max_files/1</a></td><td></td></tr><tr><td valign="top"><a href="#max_files-1">max_files/1</a></td><td></td></tr><tr><td valign="top"><a href="#rdb_indexes-0">rdb_indexes/0</a></td><td></td></tr><tr><td valign="top"><a href="#rdb_indexes-1">rdb_indexes/1</a></td><td></td></tr><tr><td valign="top"><a href="#rdb_tabs-0">rdb_tabs/0</a></td><td></td></tr><tr><td valign="top"><a href="#rdb_tabs-1">rdb_tabs/1</a></td><td></td></tr><tr><td valign="top"><a href="#write_buffer-1">write_buffer/1</a></td><td></td></tr></table>
+
+
+<a name="functions"></a>
+
+## Function Details ##
+
+<a name="cache-1"></a>
+
+### cache/1 ###
+
+`cache(X1) -> any()`
+
+<a name="calc_sizes-0"></a>
+
+### calc_sizes/0 ###
+
+`calc_sizes() -> any()`
+
+<a name="calc_sizes-1"></a>
+
+### calc_sizes/1 ###
+
+`calc_sizes(D) -> any()`
+
+<a name="count_rdb_tabs-0"></a>
+
+### count_rdb_tabs/0 ###
+
+`count_rdb_tabs() -> any()`
+
+<a name="count_rdb_tabs-1"></a>
+
+### count_rdb_tabs/1 ###
+
+`count_rdb_tabs(Db) -> any()`
+
+<a name="default-1"></a>
+
+### default/1 ###
+
+`default(X1) -> any()`
+
+<a name="describe_env-0"></a>
+
+### describe_env/0 ###
+
+`describe_env() -> any()`
+
+<a name="get_avail_ram-0"></a>
+
+### get_avail_ram/0 ###
+
+`get_avail_ram() -> any()`
+
+<a name="get_maxfiles-0"></a>
+
+### get_maxfiles/0 ###
+
+`get_maxfiles() -> any()`
+
+<a name="get_maxfiles-1"></a>
+
+### get_maxfiles/1 ###
+
+`get_maxfiles(X1) -> any()`
+
+<a name="ideal_max_files-0"></a>
+
+### ideal_max_files/0 ###
+
+`ideal_max_files() -> any()`
+
+<a name="ideal_max_files-1"></a>
+
+### ideal_max_files/1 ###
+
+`ideal_max_files(D) -> any()`
+
+<a name="max_files-1"></a>
+
+### max_files/1 ###
+
+`max_files(X1) -> any()`
+
+<a name="rdb_indexes-0"></a>
+
+### rdb_indexes/0 ###
+
+`rdb_indexes() -> any()`
+
+<a name="rdb_indexes-1"></a>
+
+### rdb_indexes/1 ###
+
+`rdb_indexes(Db) -> any()`
+
+<a name="rdb_tabs-0"></a>
+
+### rdb_tabs/0 ###
+
+`rdb_tabs() -> any()`
+
+<a name="rdb_tabs-1"></a>
+
+### rdb_tabs/1 ###
+
+`rdb_tabs(Db) -> any()`
+
+<a name="write_buffer-1"></a>
+
+### write_buffer/1 ###
+
+`write_buffer(X1) -> any()`
+

doc/mrdb_index.md

@@ -0,0 +1,99 @@
+
+
+# Module mrdb_index #
+* [Data Types](#types)
+* [Function Index](#index)
+* [Function Details](#functions)
+
+<a name="types"></a>
+
+## Data Types ##
+
+
+
+
+### <a name="type-index_value">index_value()</a> ###
+
+
+<pre><code>
+index_value() = any()
+</code></pre>
+
+
+
+
+### <a name="type-iterator_action">iterator_action()</a> ###
+
+
+<pre><code>
+iterator_action() = <a href="http://www.erlang.org/doc/man/mrdb.html#type-iterator_action">mrdb:iterator_action()</a>
+</code></pre>
+
+
+
+
+### <a name="type-ix_iterator">ix_iterator()</a> ###
+
+
+<pre><code>
+ix_iterator() = #mrdb_ix_iter{i = <a href="http://www.erlang.org/doc/man/mrdb.html#type-iterator">mrdb:iterator()</a>, type = set | bag, sub = <a href="http://www.erlang.org/doc/man/mrdb.html#type-ref">mrdb:ref()</a> | pid()}
+</code></pre>
+
+
+
+
+### <a name="type-object">object()</a> ###
+
+
+<pre><code>
+object() = tuple()
+</code></pre>
+
+<a name="index"></a>
+
+## Function Index ##
+
+
+<table width="100%" border="1" cellspacing="0" cellpadding="2" summary="function index"><tr><td valign="top"><a href="#iterator-2">iterator/2</a></td><td></td></tr><tr><td valign="top"><a href="#iterator_close-1">iterator_close/1</a></td><td></td></tr><tr><td valign="top"><a href="#iterator_move-2">iterator_move/2</a></td><td></td></tr><tr><td valign="top"><a href="#with_iterator-3">with_iterator/3</a></td><td></td></tr></table>
+
+
+<a name="functions"></a>
+
+## Function Details ##
+
+<a name="iterator-2"></a>
+
+### iterator/2 ###
+
+<pre><code>
+iterator(Tab::<a href="http://www.erlang.org/doc/man/mrdb.html#type-ref_or_tab">mrdb:ref_or_tab()</a>, IxPos::<a href="http://www.erlang.org/doc/man/mrdb.html#type-index_position">mrdb:index_position()</a>) -&gt; {ok, <a href="#type-ix_iterator">ix_iterator()</a>} | {error, term()}
+</code></pre>
+<br />
+
+<a name="iterator_close-1"></a>
+
+### iterator_close/1 ###
+
+<pre><code>
+iterator_close(Mrdb_ix_iter::<a href="#type-ix_iterator">ix_iterator()</a>) -&gt; ok
+</code></pre>
+<br />
+
+<a name="iterator_move-2"></a>
+
+### iterator_move/2 ###
+
+<pre><code>
+iterator_move(Mrdb_ix_iter::<a href="#type-ix_iterator">ix_iterator()</a>, Dir::<a href="#type-iterator_action">iterator_action()</a>) -&gt; {ok, <a href="#type-index_value">index_value()</a>, <a href="#type-object">object()</a>} | {error, term()}
+</code></pre>
+<br />
+
+<a name="with_iterator-3"></a>
+
+### with_iterator/3 ###
+
+<pre><code>
+with_iterator(Tab::<a href="http://www.erlang.org/doc/man/mrdb.html#type-ref_or_tab">mrdb:ref_or_tab()</a>, IxPos::<a href="http://www.erlang.org/doc/man/mrdb.html#type-index_position">mrdb:index_position()</a>, Fun::fun((<a href="#type-ix_iterator">ix_iterator()</a>) -&gt; Res)) -&gt; Res
+</code></pre>
+<br />
+

doc/mrdb_mutex.md

@@ -0,0 +1,30 @@
+
+
+# Module mrdb_mutex #
+* [Function Index](#index)
+* [Function Details](#functions)
+
+<a name="index"></a>
+
+## Function Index ##
+
+
+<table width="100%" border="1" cellspacing="0" cellpadding="2" summary="function index"><tr><td valign="top"><a href="#do-2">do/2</a></td><td></td></tr><tr><td valign="top"><a href="#ensure_tab-0">ensure_tab/0</a></td><td></td></tr></table>
+
+
+<a name="functions"></a>
+
+## Function Details ##
+
+<a name="do-2"></a>
+
+### do/2 ###
+
+`do(Rsrc, F) -> any()`
+
+<a name="ensure_tab-0"></a>
+
+### ensure_tab/0 ###
+
+`ensure_tab() -> any()`
+

doc/mrdb_select.md

@@ -0,0 +1,48 @@
+
+
+# Module mrdb_select #
+* [Function Index](#index)
+* [Function Details](#functions)
+
+<a name="index"></a>
+
+## Function Index ##
+
+
+<table width="100%" border="1" cellspacing="0" cellpadding="2" summary="function index"><tr><td valign="top"><a href="#fold-5">fold/5</a></td><td></td></tr><tr><td valign="top"><a href="#rdb_fold-5">rdb_fold/5</a></td><td></td></tr><tr><td valign="top"><a href="#select-1">select/1</a></td><td></td></tr><tr><td valign="top"><a href="#select-3">select/3</a></td><td></td></tr><tr><td valign="top"><a href="#select-4">select/4</a></td><td></td></tr></table>
+
+
+<a name="functions"></a>
+
+## Function Details ##
+
+<a name="fold-5"></a>
+
+### fold/5 ###
+
+`fold(Ref, Fun, Acc, MS, Limit) -> any()`
+
+<a name="rdb_fold-5"></a>
+
+### rdb_fold/5 ###
+
+`rdb_fold(Ref, Fun, Acc, Prefix, Limit) -> any()`
+
+<a name="select-1"></a>
+
+### select/1 ###
+
+`select(Cont) -> any()`
+
+<a name="select-3"></a>
+
+### select/3 ###
+
+`select(Ref, MS, Limit) -> any()`
+
+<a name="select-4"></a>
+
+### select/4 ###
+
+`select(Ref, MS, AccKeys, Limit) -> any()`
+

doc/overview.edoc

@@ -0,0 +1,250 @@
+@author Ulf Wiger <ulf@wiger.net>
+@copyright 2013-21 Klarna AB
+@title Mnesia Rocksdb - Rocksdb backend plugin for Mnesia
+
+@doc
+
+The Mnesia DBMS, part of Erlang/OTP, supports 'backend plugins', making
+it possible to utilize more capable key-value stores than the `dets'
+module (limited to 2 GB per table). Unfortunately, this support is
+undocumented. Below, some informal documentation for the plugin system
+is provided.
+
+== Table of Contents ==
+<ol>
+<li>{@section Usage}</li>
+   <ol>
+   <li>{@section Prerequisites}</li>
+   <li>{@section Getting started}</li>
+   <li>{@section Special features}</li>
+   <li>{@section Customization}</li>
+   <li>{@section Handling of errors in write operations}</li>
+   <li>{@section Caveats}</li>
+   </ol>
+<li>{@section Mnesia backend plugins}</li>
+   <ol>
+   <li>{@section Background}</li>
+   <li>{@section Design}</li>
+   </ol>
+<li>{@section Mnesia index plugins}</li>
+<li>{@section Rocksdb}</li>
+</ol>
+
+== Usage ==
+
+=== Prerequisites ===
+
+<ul>
+<li>rocksdb (included as dependency)</li>
+<li>sext (included as dependency)</li>
+<li>Erlang/OTP 21.0 or newer (https://github.com/erlang/otp)</li>
+</ul>
+
+=== Getting started ===
+
+Call `mnesia_rocksdb:register()' immediately after
+starting mnesia.
+
+Put `{rocksdb_copies, [node()]}' into the table definitions of
+tables you want to be in RocksDB.
+
+=== Special features ===
+
+RocksDB tables support efficient selects on <em>prefix keys</em>.
+
+The backend uses the `sext' module (see
+[https://github.com/uwiger/sext]) for mapping between Erlang terms and the
+binary data stored in the tables. This provides two useful properties:
+
+<ul>
+<li>The records are stored in the Erlang term order of their keys.</li>
+<li>A prefix of a composite key is ordered just before any key for which
+  it is a prefix. For example, ``{x, '_'}'' is a prefix for keys `{x, a}',
+  `{x, b}' and so on.</li>
+</ul>
+
+This means that a prefix key identifies the start of the sequence of
+entries whose keys match the prefix. The backend uses this to optimize
+selects on prefix keys.
+
+### Customization
+
+RocksDB supports a number of customization options. These can be specified
+by providing a `{Key, Value}' list named `rocksdb_opts' under `user_properties',
+for example:
+
+```
+mnesia:create_table(foo, [{rocksdb_copies, [node()]},
+                          ...
+                          {user_properties,
+                              [{rocksdb_opts, [{max_open_files, 1024}]}]
+                          }])
+'''
+
+Consult the <a href="https://github.com/facebook/rocksdb/wiki/Setup-Options-and-Basic-Tuning">RocksDB documentation</a>
+for information on configuration parameters. Also see the section below on handling write errors.
+
+The default configuration for tables in `mnesia_rocksdb' is:
+```
+default_open_opts() ->
+    [ {create_if_missing, true}
+      , {cache_size,
+         list_to_integer(get_env_default("ROCKSDB_CACHE_SIZE", "32212254"))}
+      , {block_size, 1024}
+      , {max_open_files, 100}
+      , {write_buffer_size,
+         list_to_integer(get_env_default(
+                           "ROCKSDB_WRITE_BUFFER_SIZE", "4194304"))}
+      , {compression,
+         list_to_atom(get_env_default("ROCKSDB_COMPRESSION", "true"))}
+      , {use_bloomfilter, true}
+    ].
+'''
+
+It is also possible, for larger databases, to produce a tuning parameter file.
+This is experimental, and mostly copied from `mnesia_leveldb'. Consult the
+source code in `mnesia_rocksdb_tuning.erl' and `mnesia_rocksdb_params.erl'.
+Contributions are welcome.
+
+=== Caveats ===
+
+Avoid placing `bag' tables in RocksDB. Although they work, each write
+requires additional reads, causing substantial runtime overheads. There
+are better ways to represent and process bag data (see above about
+<em>prefix keys</em>).
+
+The `mnesia:table_info(T, size)' call always returns zero for RocksDB
+tables. RocksDB itself does not track the number of elements in a table, and
+although it is possible to make the `mnesia_rocksdb' backend maintain a size
+counter, it incurs a high runtime overhead for writes and deletes since it
+forces them to first do a read to check the existence of the key. If you
+depend on having an up to date size count at all times, you need to maintain
+it yourself. If you only need the size occasionally, you may traverse the
+table to count the elements.
+
+== Mnesia backend plugins ==
+
+=== Background ===
+
+Mnesia was initially designed to be a RAM-only DBMS, and Erlang's
+`ets' tables were developed for this purpose. In order to support
+persistence, e.g. for configuration data, a disk-based version of `ets'
+(called `dets') was created. The `dets' API mimicks the `ets' API,
+and `dets' is quite convenient and fast for (nowadays) small datasets.
+However, using a 32-bit bucket system, it is limited to 2GB of data.
+It also doesn't support ordered sets. When used in Mnesia, dets-based
+tables are called `disc_only_copies'.
+
+To circumvent these limitations, another table type, called `disc_copies'
+was added. This is a combination of `ets' and `disk_log', where Mnesia
+periodically snapshots the `ets' data to a log file on disk, and meanwhile
+maintains a log of updates, which can be applied at startup. These tables
+are quite performant (especially on read access), but all data is kept in
+RAM, which can become a serious limitation.
+
+A backend plugin system was proposed by Ulf Wiger in 2016, and further
+developed with Klarna's support, to finally become included in OTP 19.
+Klarna uses a LevelDb backend, but Aeternity, in 2017, instead chose
+to implement a Rocksdb backend plugin.
+
+== Design ==
+
+As backend plugins were added on a long-since legacy-stable Mnesia,
+they had to conform to the existing code structure. For this reason,
+the plugin callbacks hook into the already present low-level access
+API in the `mnesia_lib' module. As a consequence, backend plugins have
+the same access semantics and granularity as `ets' and `dets'. This
+isn't much of a disadvantage for key-value stores like LevelDb and RocksDB,
+but a more serious issue is that the update part of this API is called
+on <em>after</em> the point of no return. That is, Mnesia does not expect
+these updates to fail, and has no recourse if they do. As an aside,
+this could also happen if a `disc_only_copies' table exceeds the 2 GB
+limit (mnesia will not check it, and `dets' will not complain, but simply
+drop the update.)
+
+== Mnesia index plugins ==
+
+When adding support for backend plugins, index plugins were also added. Unfortunately, they remain undocumented.
+
+An index plugin can be added in one of two ways:
+
+<ol>
+<li>When creating a schema, provide `{index_plugins, [{Name, Module, Function}]}' options.</li>
+<li>Call the function `mnesia_schema:add_index_plugin(Name, Module, Function)'</li>
+</ol>
+
+`Name' must be an atom wrapped as a 1-tuple, e.g. `{words}'.
+
+The plugin callback is called as `Module:Function(Table, Pos, Obj)', where `Pos=={words}' in
+our example. It returns a list of index terms.
+
+<strong>Example</strong>
+
+Given the following index plugin implementation:
+
+```
+-module(words).
+-export([words_f/3]).
+
+words_f(_,_,Obj) when is_tuple(Obj) ->
+    words_(tuple_to_list(Obj)).
+
+words_(Str) when is_binary(Str) ->
+    string:lexemes(Str, [$\s, $\n, [$\r,$\n]]);
+words_(L) when is_list(L) ->
+    lists:flatmap(fun words_/1, L);
+words_(_) ->
+    [].
+'''
+
+We can register the plugin and use it in table definitions:
+
+```
+Eshell V12.1.3  (abort with ^G)
+1> mnesia:start().
+ok
+2> mnesia_schema:add_index_plugin({words}, words, words_f).
+{atomic,ok}
+3> mnesia:create_table(i, [{index, [{words}]}]).
+{atomic,ok}
+'''
+
+Note that in this case, we had neither a backend plugin, nor even a persistent schema.
+Index plugins can be used with all table types. The registered indexing function (arity 3) must exist
+as an exported function along the node's code path.
+
+To see what happens when we insert an object, we can turn on call trace.
+
+```
+4> dbg:tracer().
+{ok,<0.108.0>}
+5> dbg:tp(words, x).
+{ok,[{matched,nonode@nohost,3},{saved,x}]}
+6> dbg:p(all,[c]).
+{ok,[{matched,nonode@nohost,60}]}
+7> mnesia:dirty_write({i,<<"one two">>, [<<"three">>, <<"four">>]}).
+(<0.84.0>) call words:words_f(i,{words},{i,<<"one two">>,[<<"three">>,<<"four">>]})
+(<0.84.0>) returned from words:words_f/3 -> [<<"one">>,<<"two">>,<<"three">>,
+                                             <<"four">>]
+(<0.84.0>) call words:words_f(i,{words},{i,<<"one two">>,[<<"three">>,<<"four">>]})
+(<0.84.0>) returned from words:words_f/3 -> [<<"one">>,<<"two">>,<<"three">>,
+                                             <<"four">>]
+ok
+8> dbg:ctp('_'), dbg:stop().
+ok
+9> mnesia:dirty_index_read(i, <<"one">>, {words}).
+[{i,<<"one two">>,[<<"three">>,<<"four">>]}]
+'''
+
+(The fact that the indexing function is called twice, seems like a performance bug.)
+
+We can observe that the indexing callback is able to operate on the whole object.
+It needs to be side-effect free and efficient, since it will be called at least once for each update
+(if an old object exists in the table, the indexing function will be called on it too, before it is
+replaced by the new object.)
+
+== Rocksdb ==
+
+== Usage ==
+
+@end

doc/plugin-userguide.md

@@ -0,0 +1,300 @@
+
+
+# Using Mnesia Plugins #
+
+Copyright (c) 2017-21 Aeternity Anstalt. All Rights Reserved.
+
+__Authors:__ Ulf Wiger ([`ulf@wiger.net`](mailto:ulf@wiger.net)).
+
+The Mnesia DBMS, part of Erlang/OTP, supports 'backend plugins', making
+it possible to utilize more capable key-value stores than the `dets`
+module (limited to 2 GB per table). Unfortunately, this support is
+undocumented. Below, some informal documentation for the plugin system
+is provided.
+
+This user guide illustrates these concepts using `mnesia_rocksdb`
+as an example.
+
+We will deal with two types of plugin:
+1. backend plugins
+2. index plugins
+
+A backend plugin is a module that implements a `mnesia_backend_type`
+behavior. Each plugin can support any number of `aliases`, which
+combined with the plugin module make up a `backend_type`.
+
+When using `mnesia_rocksdb`, the default alias is `rocksdb_copies`,
+and it is registered as a `{rocksdb_copies, mnesia_rocksdb}` pair.
+Once registered, the alias can be used just like the built-in
+backend types `ram_copies`, `disc_copies`, `disc_only_copies`.
+Mnesia asks the plugin module which one of the built-in types'
+semantics the new type is supposed to mimick: ram-only, ram+disk
+or disk-only. This is mainly relevant for how Mnesia checkpoints and
+backs up data.
+
+### <a name="Table_of_Contents">Table of Contents</a> ###
+
+1. [Usage](#Usage)
+   1. [Prerequisites](#Prerequisites)
+   2. [Getting started](#Getting_started)
+   3. [New indexing functionality](#New_indexing_functionality)
+
+## Usage
+
+### Prerequisites
+
+- rocksdb (included as dependency)
+- sext (included as dependency)
+- Erlang/OTP 22.0 or newer (https://github.com/erlang/otp)
+
+### Getting started
+
+For the purposes of this user guide, we assume an unnamed, single node
+mnesia installation. The only place where plugins are affected by
+distributed Mnesia, is in the table sync callbacks. The simplest way
+to get all paths in order for experimentation is to check out
+`mnesia_rocksdb`, building it, and then calling `rebar3 shell`. Unless
+we note otherwise, this is how a node has been started for each example.
+
+> Erlang shell interactions have been slightly beautified by eliding
+> some text and breaking and indenting some lines
+
+#### Adding a backend type to mnesia
+
+There are three different ways, all undocumented, to register a
+backend plugin in mnesia:
+
+1. Add a `backend_types` option when creating the schema, using
+   `mnesia:create_schema/2`
+
+```erlang
+Erlang/OTP 22 [erts-10.7] ...
+
+Eshell V10.7  (abort with ^G)
+1> mnesia:create_schema([node()],
+                        [{backend_types,[{rocksdb_copies,mnesia_rocksdb}]}]).
+ok
+2> mnesia:start().
+ok
+3> mnesia_schema:backend_types().
+[ram_copies,disc_copies,disc_only_copies,rocksdb_copies]
+```
+
+(In `mnesia_rocksdb`, a shortcut for this exists in `mnesia_rocksdb:create_schema(Nodes)`.)
+
+2. Add it when starting mnesia, using `mnesia:start/1` (undocumented)
+
+```erlang
+Eshell V10.7  (abort with ^G)
+1> mnesia:create_schema([node()]).
+ok
+2> mnesia:start([{schema,[{backend_types,
+                           [{rocksdb_copies,mnesia_rocksdb}]}]}]).
+ok
+3> mnesia_schema:backend_types().
+[ram_copies,disc_copies,disc_only_copies]
+```
+
+3. Call `mnesia_schema:add_backend_type/2` when mnesia is running.
+
+```erlang
+Eshell V10.7  (abort with ^G)
+1> mnesia:create_schema([node()]).
+ok
+2> mnesia:start().
+ok
+3> mnesia_schema:add_backend_type(rocksdb_copies,mnesia_rocksdb).
+{atomic,ok}
+4> mnesia_schema:backend_types().
+[ram_copies,disc_copies,disc_only_copies,rocksdb_copies]
+```
+
+In all cases the schema is updated, and other nodes, and subsequently
+added nodes, will automatically receive the information.
+The function `mnesia_schema:backend_types()` shows which backend plugin
+aliases are registered.
+
+The information is also displayed when calling `mnesia:info()`:
+
+```erlang
+5> mnesia:info().
+---> Processes holding locks <---
+---> Processes waiting for locks <---
+---> Participant transactions <---
+---> Coordinator transactions <---
+---> Uncertain transactions <---
+---> Active tables <---
+schema         : with 1        records occupying 443      words of mem
+===> System info in version "4.16.3", debug level = none <===
+opt_disc. Directory "/.../Mnesia.nonode@nohost" is used.
+use fallback at restart = false
+running db nodes   = [nonode@nohost]
+stopped db nodes   = []
+master node tables = []
+backend types      = rocksdb_copies - mnesia_rocksdb
+remote             = []
+ram_copies         = []
+disc_copies        = [schema]
+disc_only_copies   = []
+[{nonode@nohost,disc_copies}] = [schema]
+2 transactions committed, 0 aborted, 0 restarted, 0 logged to disc
+0 held locks, 0 in queue; 0 local transactions, 0 remote
+0 transactions waits for other nodes: []
+ok
+```
+
+To illustrate how mnesia persists the information in the schema:
+
+```erlang
+6> mnesia:table_info(schema,user_properties).
+[{mnesia_backend_types,[{rocksdb_copies,mnesia_rocksdb}]}]
+```
+
+#### Rocksdb registration shortcut
+
+Call `mnesia_rocksdb:register()` after starting mnesia.
+
+#### Creating a table
+
+Put `{rocksdb_copies, [node()]}` into the table definitions of
+tables you want to be in RocksDB.
+
+```erlang
+4> mnesia:create_table(t, [{rocksdb_copies,[node()]}]).
+{atomic,ok}
+5> rr(mnesia).
+[commit,cstruct,cyclic,decision,log_header,mnesia_select,
+ tid,tidstore]
+6> mnesia:table_info(t,cstruct).
+#cstruct{name = t,type = set,ram_copies = [],
+         disc_copies = [],disc_only_copies = [],
+         external_copies = [{{rocksdb_copies,mnesia_rocksdb},
+                             [nonode@nohost]}],
+         load_order = 0,access_mode = read_write,majority = false,
+         index = [],snmp = [],local_content = false,record_name = t,
+         attributes = [key,val],
+         user_properties = [],frag_properties = [],
+         storage_properties = [],
+         cookie = {{1621758137965715000,-576460752303423420,1},
+                   nonode@nohost},
+         version = {{2,0},[]}}
+```
+
+In the example above, we take a peek at the `cstruct`, which is the
+internal metadata structure for mnesia tables. The attribute showing
+that the table has been created with a `rocksdb_copies` instance, is
+the `external_copies` attribute. It lists the alias, the callback module
+and the nodes, where the instances reside.
+
+The table works essentially like one of the built-in table types.
+If we want to find out which type, we can query the callback module:
+
+```erlang
+8> mnesia_rocksdb:semantics(rocksdb_copies, storage).
+disc_only_copies
+```
+
+Consult the `mnesia_rocksdb` man page for more info on the
+`Mod:semantics/2` function.
+
+### New indexing functionality
+
+With the introduction of backend plugins, a few improvements were made
+to mnesia's indexing support.
+
+#### Persistent indexes
+
+In the past, and still with the built-in types, indexes were always
+rebuilt on startup. Since backend plugins were introduced mainly in
+order to support very large tables, a couple of callback functions
+were added in order to detect whether a full rebuild is needed.
+
+> The callback functions are `Mod:is_index_consistent/2` and
+> `Mod:index_is_consistent/3`.
+> The first function (figuratively) always returns `false` for indexes
+> on built-in table types. Backend plugin modules should always return
+> `false` if they have no information. After building the index, mnesia
+> calls `Mod:index_is_consistent(Alias, IxTab, true)`, and the callback
+> is expected to persist this information. `IxTab`, in this case, is
+> a logical name for the index 'table': `{Tab, index, PosInfo}`
+
+#### Ordered indexes
+
+A problem in the past with mnesia indexing has been that indexes with
+very large fan-out were inefficient. Indexes were represented as `bag`
+tables, and the cost of inserting a secondary key was proportional to
+the number of identical secondary keys already in the index.
+
+When adding the backend plugin support - also not least because the
+first candidate LevelDb didn't do bags well - support for ordered
+indexes was added. They turn out to be have much more stable performance
+for indexes with large fan-out. They also work on all built-in table
+types.
+
+When creating an index, you can specify the type of index as `bag` or
+`ordered`. If you omit the type, it will default to `bag` for built-in
+table types, and for external types, whatever is the first type in the
+list of supported index types returned by `Mod:semantics(Alias, index_types)`.
+
+> For `mnesia_rocksdb`, only `ordered` is supported, but a bug in mnesia
+> makes it ignore this, and try to create a bag index anyway. The
+> `mnesia_rocksdb` plugin rejects this.
+> Note that while e.g. mnesia_rocksdb supports regular bag tables, they are not
+> efficiently implemented.
+
+Mnesia currently doesn't allow specifying an index type in
+`mnesia:add_table_index/2`, so simply indicate the index position,
+and let the backend choose the default.
+
+Having ordered indexes opens up for some new possibilities, but
+there are currently no functions in mnesia such as index_first, index_next
+etc., or performing a select in index order.
+
+#### Index plugins
+
+Index plugins are a great new feature, also almost entirely undocumented.
+
+An index plugin is a registered indexing function, which can operate
+on the entire object, and shall return a list of secondary keys.
+When registering an index plugin, it is given an alias, a callback module,
+and an function name, not unlike backend plugins. The index plugin alias
+must be an atom wrapped inside a 1-tuple, i.e. `{atom()}`.
+
+To illustrate, we use a sample indexing function implemented in
+mnesia_rocksdb, which checks all non-key attributes of an object,
+and for each value that is a list, makes each list element a secondary
+key value.
+
+```erlang
+9> mnesia_schema:add_index_plugin({lv}, mnesia_rocksdb, ix_listvals). 
+{atomic,ok}
+10> mnesia:add_table_index(t,{lv}).
+{atomic,ok}
+11> mnesia:dirty_write({t,1,[a,b]}).
+ok
+12> mnesia:dirty_write({t,2,[b,c]}).
+ok
+13> mnesia:dirty_index_read(t,a,{lv}).
+[{t,1,[a,b]}]
+14> mnesia:dirty_index_read(t,b,{lv}).
+[{t,1,[a,b]},{t,2,[b,c]}]
+15> mnesia:dirty_index_read(t,c,{lv}).
+[{t,2,[b,c]}]
+```
+
+For clarity, this is the implementation of the index callback:
+
+```erlang
+ix_listvals(_Tab, _Pos, Obj) ->
+    lists:foldl(
+      fun(V, Acc) when is_list(V) ->
+              V ++ Acc;
+         (_, Acc) ->
+              Acc
+      end, [], tl(tuple_to_list(Obj))).
+```
+
+Note that the index callback must be a pure function, as it
+is also relied upon when deleting objects. That is, it must
+always return the same values when called with a specific
+set of input arguments.

doc/stylesheet.css

@@ -0,0 +1,55 @@
+/* standard EDoc style sheet */
+body {
+	font-family: Verdana, Arial, Helvetica, sans-serif;
+      	margin-left: .25in;
+       	margin-right: .2in;
+       	margin-top: 0.2in;
+       	margin-bottom: 0.2in;
+       	color: #000000;
+       	background-color: #ffffff;
+}
+h1,h2 {
+ 	margin-left: -0.2in;
+}
+div.navbar {
+	background-color: #add8e6;
+	padding: 0.2em;
+}
+h2.indextitle {
+	padding: 0.4em;
+	background-color: #add8e6;
+}
+h3.function,h3.typedecl {
+	background-color: #add8e6;
+ 	padding-left: 1em;
+}
+div.spec {
+ 	margin-left: 2em;
+	background-color: #eeeeee;
+}
+a.module {
+	text-decoration:none
+}
+a.module:hover {
+	background-color: #eeeeee;
+}
+ul.definitions {
+	list-style-type: none;
+}
+ul.index {
+	list-style-type: none;
+	background-color: #eeeeee;
+}
+
+/*
+ * Minor style tweaks
+ */
+ul {
+	list-style-type: square;
+}
+table {
+	border-collapse: collapse;
+}
+td {
+	padding: 3
+}

erlang_ls.config

@@ -0,0 +1,7 @@
+deps_dirs:
+  - "_build/default/lib/*"
+include_paths:
+  - "src/*"
+include_dirs:
+  - "include"
+  - "_build/default/lib"

include/mnesia_rocksdb.hrl

@@ -0,0 +1,15 @@
+
+%% Data and meta data (a.k.a. info) are stored in the same table.
+%% This is a table of the first byte in data
+%% 0    = before meta data
+%% 1    = meta data
+%% 2    = before data
+%% >= 8 = data
+
+-define(INFO_START, 0).
+-define(INFO_TAG, 1).
+-define(DATA_START, 2).
+-define(BAG_CNT, 32).   % Number of bits used for bag object counter
+-define(MAX_BAG, 16#FFFFFFFF).
+
+-define(VSN, 2).

rebar.config

@@ -4,14 +4,40 @@
 {deps,
  [
   {sext, "1.8.0"},
-  {rocksdb,"1.7.0"}
+  {rocksdb, {git, "https://gitlab.com/seanhinde/erlang-rocksdb.git", {ref,"9ae37839"}}},
+  {hut, "1.3.0"}
  ]}.
 
+{xref_checks, [
+    undefined_function_calls,
+    locals_not_used,
+    deprecated_function_calls
+]}.
+
 {profiles,
  [
   {test,
    [
-    {deps, [ {proper, "1.3.0"}
+    {deps, [ {proper, "1.4.0"}
-           , {meck, "0.9.0"}]}
+           , {meck, "0.9.2"}
-   ]}
+           , {trace_runner, {git, "https://github.com/uwiger/trace_runner.git",
+                             {ref, "2e56677"}}}
+           ]}
+   ]},
+  {edown,
+   %% Use as `rebar3 as edown do edoc`
+   [
+    {deps, [{edown, "0.8.4"}]},
+    {edoc_opts,
+     [{doclet, edown_doclet},
+      {app_default, "http://www.erlang.org/doc/man"},
+      {doc_path, []},
+      {top_level_readme,
+       {"./README.md", "https://github.com/aeternity/mnesia_rocksdb"}}]}]}
  ]}.
+
+{ex_doc, [
+     {extras, [<<"README.md">>, <<"LICENSE">>]},
+     {main, <<"readme">>},
+     {source_url, <<"https://github.com/aeternity/mnesia_rocksdb">>}
+]}.

rebar.lock

@@ -1,11 +1,15 @@
 {"1.2.0",
-[{<<"rocksdb">>,{pkg,<<"rocksdb">>,<<"1.7.0">>},0},
+[{<<"hut">>,{pkg,<<"hut">>,<<"1.3.0">>},0},
+ {<<"rocksdb">>,
+  {git,"https://gitlab.com/seanhinde/erlang-rocksdb.git",
+       {ref,"9ae378391ffc94200bde24efcd7a4921eba688d0"}},
+  0},
  {<<"sext">>,{pkg,<<"sext">>,<<"1.8.0">>},0}]}.
 [
 {pkg_hash,[
- {<<"rocksdb">>, <<"5D23319998A7FCE5FFD5D7824116C905CABA7F91BAF8EDDABD0180F1BB272CEF">>},
+ {<<"hut">>, <<"71F2F054E657C03F959CF1ACC43F436EA87580696528CA2A55C8AFB1B06C85E7">>},
  {<<"sext">>, <<"90A95B889F5C781B70BBCF44278B763148E313C376B60D87CE664CB1C1DD29B5">>}]},
 {pkg_hash_ext,[
- {<<"rocksdb">>, <<"A4BDC5DD80ED137161549713062131E8240523787EBE7B51DF61CFB48B1786CE">>},
+ {<<"hut">>, <<"7E15D28555D8A1F2B5A3A931EC120AF0753E4853A4C66053DB354F35BF9AB563">>},
  {<<"sext">>, <<"BC6016CB8690BAF677EACACFE6E7CADFEC8DC7E286CBBED762F6CD55B0678E73">>}]}
 ].

src/mnesia_rocksdb.app.src

@@ -1,3 +1,4 @@
+%% -*- mode: erlang; erlang-indent-level: 4; indent-tabs-mode: nil -*-
 {application, mnesia_rocksdb,
  [
   {description, "RocksDB backend plugin for Mnesia"},

src/mnesia_rocksdb_app.erl

@@ -1,3 +1,4 @@
+%% -*- mode: erlang; erlang-indent-level: 4; indent-tabs-mode: nil -*-
 %%----------------------------------------------------------------
 %% Copyright (c) 2013-2016 Klarna AB
 %%

src/mnesia_rocksdb_int.hrl

@@ -0,0 +1,18 @@
+%% -*- mode: erlang; erlang-indent-level: 4; indent-tabs-mode: nil -*-
+-include_lib("hut/include/hut.hrl").
+
+%% enable debugging messages through mnesia:set_debug_level(debug)
+-ifndef(MNESIA_ROCKSDB_NO_DBG).
+-define(dbg(Fmt, Args), ?log(debug, Fmt, Args)).
+%% -define(dbg(Fmt, Args),
+%%         %% avoid evaluating Args if the message will be dropped anyway
+%%         case mnesia_monitor:get_env(debug) of
+%%             none -> ok;
+%%             verbose -> ok;
+%%             _ -> mnesia_lib:dbg_out("~p:~p: "++(Fmt),[?MODULE,?LINE|Args])
+%%         end).
+-else.
+-define(dbg(Fmt, Args), ok).
+-endif.
+
+-define(DEFAULT_RETRIES, 1).

src/mnesia_rocksdb_lib.erl

@@ -1,17 +1,341 @@
-%%% @doc RocksDB update  wrappers, in separate module for easy tracing and mocking.
+%%% @doc RocksDB update wrappers, in separate module for easy tracing and mocking.
 %%%
 -module(mnesia_rocksdb_lib).
 
--export([put/4,
+-export([ put/4
-         write/3,
+        , write/3
-         delete/3]).
+        , delete/3
+        ]).
 
+-export([ open_rocksdb/3
+        , data_mountpoint/1
+        , create_mountpoint/1
+        , tabname/1
+        ]).
 
+-export([ default_encoding/3
+        , check_encoding/2
+        , valid_obj_type/2
+        , valid_key_type/2 ]).
+
+-export([ keypos/1
+        , encode_key/1, encode_key/2
+        , decode_key/1, decode_key/2
+        , encode_val/1, encode_val/2
+        , decode_val/1, decode_val/3
+        , encode/2
+        , decode/2
+        ]).
+
+-include("mnesia_rocksdb.hrl").
+-include_lib("hut/include/hut.hrl").
+
+put(#{db := Ref, cf := CF}, K, V, Opts) ->
+    rocksdb:put(Ref, CF, K, V, Opts);
 put(Ref, K, V, Opts) ->
     rocksdb:put(Ref, K, V, Opts).
 
-write(Ref, L, Opts) ->
+write(#{db := Ref, cf := CF}, L, Opts) ->
-    rocksdb:write(Ref, L, Opts).
+    write_as_batch(L, Ref, CF, Opts).
 
 delete(Ref, K, Opts) ->
     rocksdb:delete(Ref, K, Opts).
+
+
+write_as_batch(L, Ref, CF, Opts) ->
+    {ok, Batch} = rocksdb:batch(),
+    lists:foreach(
+      fun({put, K, V}) ->
+              ok = rocksdb:batch_put(Batch, CF, K, V);
+         ({delete, K}) ->
+              ok = rocksdb:batch_delete(Batch, CF, K)
+      end, L),
+    rocksdb:write_batch(Ref, Batch, Opts).
+
+create_mountpoint(Tab) ->
+    MPd = data_mountpoint(Tab),
+    case filelib:is_dir(MPd) of
+        false ->
+            file:make_dir(MPd),
+            ok;
+        true ->
+            Dir = mnesia_lib:dir(),
+            case lists:prefix(Dir, MPd) of
+                true ->
+                    ok;
+                false ->
+                    {error, exists}
+            end
+    end.
+
+data_mountpoint(Tab) ->
+    Dir = mnesia_monitor:get_env(dir),
+    filename:join(Dir, tabname(Tab) ++ ".extrdb").
+
+tabname({admin, Alias}) ->
+    "mnesia_rocksdb-" ++ atom_to_list(Alias) ++ "-_db";
+tabname({Tab, index, {{Pos},_}}) ->
+    atom_to_list(Tab) ++ "-=" ++ atom_to_list(Pos) ++ "=-_ix";
+tabname({Tab, index, {Pos,_}}) ->
+    atom_to_list(Tab) ++ "-" ++ integer_to_list(Pos) ++ "-_ix";
+tabname({Tab, retainer, Name}) ->
+    atom_to_list(Tab) ++ "-" ++ retainername(Name) ++ "-_RET";
+tabname(Tab) when is_atom(Tab) ->
+    atom_to_list(Tab) ++ "-_tab".
+
+default_encoding({_, index, _}, _, _) ->
+    {sext, {value, raw}};
+default_encoding({_, retainer, _}, _, _) ->
+    {term, {value, term}};
+default_encoding(_, Type, As) ->
+    KeyEnc = case Type of
+                 ordered_set -> sext;
+                 set         -> term;
+                 bag         -> sext
+             end,
+    ValEnc = case As of
+                 [_, _] ->
+                     {value, term};
+                 [_, _ | _] ->
+                     {object, term}
+             end,
+    {KeyEnc, ValEnc}.
+
+check_encoding(Encoding, Attributes) ->
+    try check_encoding_(Encoding, Attributes)
+    catch
+        throw:Error ->
+            Error
+    end.
+
+check_encoding_({Key, Val}, As) ->
+    Key1 = check_key_encoding(Key),
+    Val1 = check_value_encoding(Val, As),
+    {ok, {Key1, Val1}};
+check_encoding_(E, _) ->
+    throw({error, {invalid_encoding, E}}).
+
+check_key_encoding(E) when E==sext; E==term; E==raw ->
+    E;
+check_key_encoding(E) ->
+    throw({error, {invalid_key_encoding, E}}).
+
+check_value_encoding(raw, [_, _]) -> {value, raw};
+check_value_encoding({value, E} = V, [_, _]) when E==term; E==raw; E==sext -> V;
+check_value_encoding({object, E} = V, _) when E==term; E==raw; E==sext -> V;
+check_value_encoding(term, As) -> {val_encoding_type(As), term};
+check_value_encoding(sext, As) -> {val_encoding_type(As), sext};
+check_value_encoding(E, _) -> 
+    throw({error, {invalid_value_encoding, E}}).
+
+val_encoding_type(Attrs) ->
+    case Attrs of
+            [_, _]   -> value;
+            [_, _|_] -> object
+    end.
+
+valid_obj_type(#{encoding := Enc}, Obj) ->
+    case {Enc, Obj} of
+        {{binary, {value, binary}}, {_, K, V}} ->
+            is_binary(K) andalso is_binary(V);
+        {{binary, _}, _} ->
+            is_binary(element(2, Obj));
+        {{_, {value, binary}}, {_, _, V}} ->
+            is_binary(V); 
+        _ ->
+            %% No restrictions on object type
+            %% unless key and/or value typed to binary
+            true 
+    end.
+
+valid_key_type(#{encoding := Enc}, Key) ->
+    case Enc of
+        {binary, _} when is_binary(Key) ->
+            true;
+        {binary, _} ->
+            false;
+        _ ->
+            true
+    end.
+
+
+-spec encode_key(any()) -> binary().
+encode_key(Key) ->
+    encode(Key, sext).
+
+encode(Value, sext) ->
+    sext:encode(Value);
+encode(Value, raw) when is_binary(Value) ->
+    Value;
+encode(Value, term) ->
+    term_to_binary(Value).
+
+
+encode_key(Key, #{encoding := {Enc,_}}) ->
+    encode(Key, Enc);
+encode_key(Key, _) ->
+    encode(Key, sext).
+
+-spec decode_key(binary()) -> any().
+decode_key(CodedKey) ->
+    decode(CodedKey, sext).
+
+decode_key(CodedKey, #{encoding := {Enc, _}}) ->
+    decode(CodedKey, Enc);
+decode_key(CodedKey, Enc) ->
+    decode(CodedKey, Enc).
+
+decode(Val, sext) ->
+    case sext:partial_decode(Val) of
+        {full, Result, _} ->
+            Result;
+        _ ->
+            error(badarg, Val)
+    end;
+decode(Val, raw) ->
+    Val;
+decode(Val, term) ->
+    binary_to_term(Val).
+
+-spec encode_val(any()) -> binary().
+encode_val(Val) ->
+    encode(Val, term).
+
+encode_val(Val, Enc) when is_atom(Enc) ->
+    encode(Val, Enc); 
+encode_val(_, #{name := {_,index,_}}) ->
+    <<>>;
+encode_val(Val, #{encoding := {_, Enc0}, attr_pos := AP}) ->
+    {Type, Enc} = enc_type(Enc0),
+    case {map_size(AP), Type} of
+        {2, value} ->
+            encode(element(3, Val), Enc);
+        {_, object} ->
+            encode(setelement(2, Val, []), Enc)
+    end.
+
+enc_type({T, _} = E) when T==value; T==object ->
+    E;
+enc_type(E) when is_atom(E) ->
+    {object, E}.
+
+-spec decode_val(binary()) -> any().
+decode_val(CodedVal) ->
+    binary_to_term(CodedVal).
+
+decode_val(<<>>, K, #{name := {_,index,_}}) ->
+    {K};
+decode_val(CodedVal, Key, Ref) ->
+    {Type, Enc} = value_encoding(Ref),
+    case Type of
+        object ->
+            setelement(2, decode(CodedVal, Enc), Key);
+        value ->
+            make_rec(Key, decode(CodedVal, Enc), Ref)
+    end.
+
+make_rec(Key, _Val, #{name := {_, index, {_,ordered}}}) ->
+    {Key};
+make_rec(Key, Val, #{properties := #{record_name := Tag}}) ->
+    {Tag, Key, Val};
+make_rec(Key, Val, #{attr_pos := AP}) ->
+    %% no record name
+    case AP of
+        #{key := 1} -> {Key, Val};
+        #{key := 2} -> {Val, Key}    %% Yeah, right, but people are weird
+    end.
+
+value_encoding(#{encoding := {_, Enc}}) ->
+    enc_type(Enc);
+value_encoding(#{}) ->
+    {object, term};
+value_encoding({Type, Enc} = E) when is_atom(Type), is_atom(Enc) ->
+    E.
+
+keypos({admin, _}) ->
+    1;
+keypos({_, index, _}) ->
+    1;
+keypos({_, retainer, _}) ->
+    2;
+keypos(Tab) when is_atom(Tab) ->
+    2.
+
+%% ======================================================================
+%% Private functions
+%% ======================================================================
+
+retainername(Name) when is_atom(Name) ->
+    atom_to_list(Name);
+retainername(Name) when is_list(Name) ->
+    try binary_to_list(list_to_binary(Name))
+    catch
+        error:_ ->
+            lists:flatten(io_lib:write(Name))
+    end;
+retainername(Name) ->
+    lists:flatten(io_lib:write(Name)).
+
+open_rocksdb(MPd, RdbOpts, CFs) ->
+    open_rocksdb(MPd, rocksdb_open_opts_(RdbOpts), CFs, get_retries()).
+
+%% Code adapted from basho/riak_kv_eleveldb_backend.erl
+open_rocksdb(MPd, Opts, CFs, Retries) ->
+    open_db(MPd, Opts, CFs, max(1, Retries), undefined).
+
+open_db(_, _, _, 0, LastError) ->
+    {error, LastError};
+open_db(MPd, Opts, CFs, RetriesLeft, _) ->
+    case rocksdb:open_optimistic_transaction_db(MPd, Opts, CFs) of
+        {ok, _Ref, _CFRefs} = Ok ->
+            ?log(debug, "Open - Rocksdb: ~s (~p) -> ~p", [MPd, Opts, Ok]),
+            Ok;
+        %% Check specifically for lock error, this can be caused if
+        %% a crashed mnesia takes some time to flush rocksdb information
+        %% out to disk. The process is gone, but the NIF resource cleanup
+        %% may not have completed.
+        {error, {db_open, OpenErr}=Reason} ->
+            case lists:prefix("IO error: lock ", OpenErr) of
+                true ->
+                    SleepFor = get_retry_delay(),
+                    ?log(debug, ("Open - Rocksdb backend retrying ~p in ~p ms"
+                                 " after error ~s"), [MPd, SleepFor, OpenErr]),
+                    timer:sleep(SleepFor),
+                    open_db(MPd, Opts, CFs, RetriesLeft - 1, Reason);
+                false ->
+                    {error, Reason}
+            end;
+        {error, Reason} ->
+            {error, Reason}
+    end.
+
+get_retries() -> 30.
+get_retry_delay() -> 100.
+
+rocksdb_open_opts_(RdbOpts) ->
+    lists:foldl(
+      fun({K,_} = Item, Acc) ->
+              lists:keystore(K, 1, Acc, Item)
+      end, default_open_opts(), RdbOpts).
+
+default_open_opts() ->
+    [ {create_if_missing, true}
+      , {cache_size,
+         list_to_integer(get_env_default("ROCKSDB_CACHE_SIZE", "32212254"))}
+      , {block_size, 1024}
+      , {max_open_files, 30}
+      , {write_buffer_size,
+         list_to_integer(get_env_default(
+                           "ROCKSDB_WRITE_BUFFER_SIZE", "4194304"))}
+      , {compression,
+         list_to_atom(get_env_default("ROCKSDB_COMPRESSION", "true"))}
+      , {use_bloomfilter, true}
+    ].
+
+get_env_default(Key, Default) ->
+    case os:getenv(Key) of
+        false ->
+            Default;
+        Value ->
+            Value
+    end.

src/mnesia_rocksdb_params.erl

@@ -1,3 +1,4 @@
+%% -*- mode: erlang; erlang-indent-level: 4; indent-tabs-mode: nil -*-
 %%----------------------------------------------------------------
 %% Copyright (c) 2013-2016 Klarna AB
 %%
@@ -33,17 +34,12 @@
          code_change/3]).
 
 -include("mnesia_rocksdb_tuning.hrl").
+-include("mnesia_rocksdb_int.hrl").
 
 -define(KB, 1024).
 -define(MB, 1024 * 1024).
 -define(GB, 1024 * 1024 * 1024).
 
--ifdef(DEBUG).
--define(dbg(Fmt, Args), io:fwrite(user,"~p:~p: "++(Fmt),[?MODULE,?LINE|Args])).
--else.
--define(dbg(Fmt, Args), ok).
--endif.
-
 lookup(Tab, Default) ->
     try ets:lookup(?MODULE, Tab) of
         [{_, Params}] ->
@@ -113,21 +109,21 @@ store_params(Params) ->
     NTabs = length(Params),
     Env0= mnesia_rocksdb_tuning:describe_env(),
     Env = Env0#tuning{n_tabs = NTabs},
-    ?dbg("Env = ~p~n", [Env]),
+    ?log(debug, "Env = ~p~n", [Env]),
     TotalFiles = lists:sum([mnesia_rocksdb_tuning:max_files(Sz) ||
                                {_, Sz} <- Params]),
-    ?dbg("TotalFiles = ~p~n", [TotalFiles]),
+    ?log(debug, "TotalFiles = ~p~n", [TotalFiles]),
     MaxFs = Env#tuning.max_files,
-    ?dbg("MaxFs = ~p~n", [MaxFs]),
+    ?log(debug, "MaxFs = ~p~n", [MaxFs]),
     FsHeadroom = MaxFs * 0.6,
-    ?dbg("FsHeadroom = ~p~n", [FsHeadroom]),
+    ?log(debug, "FsHeadroom = ~p~n", [FsHeadroom]),
     FilesFactor = if TotalFiles =< FsHeadroom ->
                           1;  % don't have to scale down
                      true ->
                           FsHeadroom / TotalFiles
                   end,
     Env1 = Env#tuning{files_factor = FilesFactor},
-    ?dbg("Env1 = ~p~n",            [Env1]),
+    ?log(debug, "Env1 = ~p~n",            [Env1]),
     lists:foreach(
       fun({Tab, Sz}) when is_atom(Tab);
                           is_atom(element(1,Tab)),

src/mnesia_rocksdb_sup.erl

@@ -1,3 +1,4 @@
+%% -*- mode: erlang; erlang-indent-level: 4; indent-tabs-mode: nil -*-
 %%----------------------------------------------------------------
 %% Copyright (c) 2013-2016 Klarna AB
 %%

src/mnesia_rocksdb_tuning.erl

@@ -1,3 +1,4 @@
+%% -*- mode: erlang; erlang-indent-level: 4; indent-tabs-mode: nil -*-
 %%----------------------------------------------------------------
 %% Copyright (c) 2013-2016 Klarna AB
 %%

src/mnesia_rocksdb_tuning.hrl

@@ -1,3 +1,4 @@
+%% -*- mode: erlang; erlang-indent-level: 4; indent-tabs-mode: nil -*-
 %%----------------------------------------------------------------
 %% Copyright (c) 2013-2016 Klarna AB
 %%

src/mrdb_index.erl

@@ -0,0 +1,192 @@
+%% -*- mode: erlang; erlang-indent-level: 4; indent-tabs-mode: nil -*-
+-module(mrdb_index).
+
+-export([
+          with_iterator/3
+        , iterator_move/2
+        , iterator/2
+        , iterator_close/1
+        ]).
+
+-record(mrdb_ix_iter, { i    :: mrdb:iterator()
+                      , type = set :: set | bag
+                      , sub  :: mrdb:ref() | pid()
+                      }).
+
+-type ix_iterator() :: #mrdb_ix_iter{}.
+-type index_value() :: any().
+-type iterator_action() :: mrdb:iterator_action().
+
+-type object() :: tuple().
+
+-record(subst, { i :: mrdb:iterator()
+               , vals_f
+               , cur
+               , mref }).
+
+-define(TIMEOUT, 5000).
+
+-import(mnesia_rocksdb_lib, [ encode_key/2 ]).
+
+-export_type([ ix_iterator/0 ]).
+
+-spec with_iterator(mrdb:ref_or_tab(), mrdb:index_position(), fun( (ix_iterator()) -> Res)) -> Res.
+with_iterator(Tab, IxPos, Fun) when is_function(Fun, 1) ->
+    {ok, I} = iterator(Tab, IxPos),
+    try Fun(I)
+    after
+        iterator_close(I)
+    end.
+
+-spec iterator(mrdb:ref_or_tab(), mrdb:index_position()) -> {ok, ix_iterator()}
+                                                          | {error, _}.
+iterator(Tab, IxPos) ->
+    #{semantics := Sem} = R = mrdb:ensure_ref(Tab),
+    #{ix_vals_f := IxValsF} = IxR = ensure_index_ref(IxPos, R),
+    case mrdb:iterator(IxR, []) of
+        {ok, I} ->
+            case Sem of
+                bag ->
+                    P = sub_new(R, IxValsF),
+                    {ok, #mrdb_ix_iter{ i = I
+                                      , sub = P }};
+                _ ->
+                    {ok, #mrdb_ix_iter{i = I, sub = R}}
+            end;
+        Err ->
+            Err
+    end.
+
+-spec iterator_move(ix_iterator(), iterator_action()) -> {ok, index_value(), object()}
+                                                       | {error, _}.
+iterator_move(#mrdb_ix_iter{type = set} = IxI, Dir) -> iterator_move_set(IxI, Dir);
+iterator_move(#mrdb_ix_iter{type = bag} = IxI, Dir) -> iterator_move_bag(IxI, Dir).
+
+iterator_move_set(#mrdb_ix_iter{i = I, sub = Sub}, Dir) ->
+    case mrdb:iterator_move(I, Dir) of
+        {ok, {{FKey, PKey}}} ->
+            {ok, FKey, opt_read(Sub, PKey)};
+        Other ->
+            Other
+    end.
+
+iterator_move_bag(#mrdb_ix_iter{i = I, sub = Sub}, Dir) ->
+    case call_sub(Sub, {move_rel, Dir}) of
+        not_found ->
+            case mrdb:iterator_move(I, Dir) of
+                {ok, {FKey, PKey}} ->
+                    call_sub(Sub, {move_abs, FKey, PKey});
+                Other ->
+                    Other
+            end;
+        Other ->
+            Other
+    end.
+
+opt_read(R, Key) ->
+    case mrdb:read(R, Key, []) of
+        [Obj] ->
+            Obj;
+        [] ->
+            []
+    end.
+
+sub_new(R, ValsF) when is_function(ValsF, 1) ->
+    Me = self(),
+    {Pid, MRef} = spawn_monitor(
+                    fun() ->
+                            MRef = monitor(process, Me),
+                            case mrdb:iterator(R) of
+                                {ok, I} ->
+                                    Me ! {self(), ok},
+                                    sub_loop(#subst{ mref   = MRef
+                                                   , i      = I
+                                                   , vals_f = ValsF
+                                                   , cur    = undefined});
+                                Error ->
+                                    Me ! {self(), Error}
+                            end
+                    end),
+    receive
+        {'DOWN', MRef, _, _, Crash} ->
+            mrdb:abort({error, Crash});
+        {Pid, ok} ->
+            demonitor(MRef),
+            Pid;
+        {Pid, Error} ->
+            demonitor(MRef),
+            mrdb:abort(Error)
+    end.
+
+sub_loop(#subst{i = I, mref = MRef} = St) ->
+    receive
+        {'DOWN', MRef, _, _, _} ->
+            mrdb:iterator_close(I);
+        {Pid, Ref, close} ->
+            mrdb:iterator_close(I),
+            Pid ! {Ref, ok};
+        {Pid, Ref, cur} ->
+            Pid ! {Ref, St#subst.cur},
+            sub_loop(St);
+        {Pid, Ref, {move, Cur, Dir}} when is_binary(Dir) ->
+            {Res, St1} = sub_abs_move(Cur, Dir, St),
+            Pid ! {Ref, Res},
+            sub_loop(St1);
+        {Pid, Ref, {move_rel, Dir}} ->
+            {Res, St1} = sub_rel_move(Dir, St),
+            Pid ! {Ref, Res},
+            sub_loop(St1)
+    end.
+
+sub_abs_move(Cur, Dir, #subst{i = I} = St) ->
+    case mrdb:iterator_move(I, Dir) of
+        {ok, _} = Ok ->
+            {Ok, St#subst{cur = Cur}};
+        Other ->
+            {Other, St#subst{cur = undefined}}
+    end.
+
+sub_rel_move(Dir, #subst{i = I, vals_f = VF, cur = Prev} = St) ->
+    case mrdb:iterator_move(I, Dir) of
+        {ok, Obj} = Ok ->
+            case lists:member(Prev, VF(Obj)) of
+                true ->
+                    {Ok, St};
+                false ->
+                    {not_found, St#subst{cur = undefined}}
+            end;
+        Other ->
+            {Other, St#subst{cur = undefined}}
+    end.
+
+call_sub(Pid, Req) ->
+    MRef = monitor(process, Pid),
+    Pid ! {self(), MRef, Req},
+    receive
+        {MRef, Reply} ->
+            demonitor(MRef),
+            Reply;
+        {'DOWN', MRef, _, _, Reason} ->
+            error(Reason)
+    after ?TIMEOUT ->
+            error(timeout)
+    end.
+
+-spec iterator_close(ix_iterator()) -> ok.
+iterator_close(#mrdb_ix_iter{i = I, sub = Sub}) ->
+    mrdb:iterator_close(I),
+    iterator_close_sub(Sub).
+
+iterator_close_sub(P) when is_pid(P) ->
+    call_sub(P, close);
+iterator_close_sub(_) ->
+    ok.
+
+ensure_index_ref(IxPos, #{name := Name, attr_pos := AP, properties := #{index := Ixs}}) ->
+    {_,ordered} = Ix = lists:keyfind(index_pos(IxPos, AP), 1, Ixs),
+    mrdb:get_ref({Name, index, Ix}).
+
+index_pos(P, AP) when is_atom(P) ->
+    maps:get(P, AP);
+index_pos(P, _) ->
+    P.

src/mrdb_mutex.erl

@@ -0,0 +1,81 @@
+%% -*- mode: erlang; erlang-indent-level: 4; indent-tabs-mode: nil -*-
+-module(mrdb_mutex).
+
+-export([ do/2 ]).
+
+-export([ ensure_tab/0 ]).
+
+-define(LOCK_TAB, ?MODULE).
+
+%% We use a wrapping ets counter (default: 0) as a form of semaphor.
+%% The claim operation is done using an atomic list of two updates:
+%% first, incrementing with 0 - this returns the previous value
+%% then, incrementing with 1, but wrapping at 1, ensuring that we get 1 back,
+%% regardless of previous value. This means that if [0,1] is returned, the resource
+%% was not locked previously; if [1,1] is returned, it was.
+%%
+%% Releasing the resource is done by deleting the resource. If we just decrement,
+%% we will end up with lingering unlocked resources, so we might as well delete.
+%% Either operation is atomic, and the claim op creates the object if it's missing.
+
+do(Rsrc, F) when is_function(F, 0) ->
+    true = claim(Rsrc),
+    try F()
+    after
+        release(Rsrc)
+    end.
+
+claim(Rsrc) ->
+    case claim_(Rsrc) of
+        true -> true;
+        false -> busy_wait(Rsrc, 1000)
+    end.
+
+claim_(Rsrc) ->
+    case ets:update_counter(?LOCK_TAB, Rsrc, [{2, 0},
+                                              {2, 1, 1, 1}], {Rsrc, 0}) of
+        [0, 1] ->
+            %% have lock
+            true;
+        [1, 1] ->
+            false
+    end.
+
+%% The busy-wait function makes use of the fact that we can read a timer to find out
+%% if it still has time remaining. This reduces the need for selective receive, looking
+%% for a timeout message. We yield, then retry the claim op. Yielding at least used to
+%% also be necessary for the `read_timer/1` value to refresh.
+%%
+busy_wait(Rsrc, Timeout) ->
+    Ref = erlang:send_after(Timeout, self(), {claim, Rsrc}),
+    do_wait(Rsrc, Ref).
+
+do_wait(Rsrc, Ref) ->
+    erlang:yield(),
+    case erlang:read_timer(Ref) of
+        false ->
+            erlang:cancel_timer(Ref),
+            error(lock_wait_timeout);
+        _ ->
+            case claim_(Rsrc) of
+                true ->
+                    erlang:cancel_timer(Ref),
+                    ok;
+                false ->
+                    do_wait(Rsrc, Ref)
+            end
+    end.
+
+release(Rsrc) ->
+    ets:delete(?LOCK_TAB, Rsrc),
+    ok.
+
+
+%% Called by the process holding the ets table.
+ensure_tab() ->
+    case ets:info(?LOCK_TAB, name) of
+        undefined ->
+            ets:new(?LOCK_TAB, [set, public, named_table, {write_concurrency, true}]);
+        _ ->
+            true
+    end.

src/mrdb_select.erl

@@ -0,0 +1,285 @@
+%% -*- mode: erlang; erlang-indent-level: 4; indent-tabs-mode: nil -*-
+-module(mrdb_select).
+
+-export([ select/3    %% (Ref, MatchSpec, Limit)
+        , select/4    %% (Ref, MatchSpec, AccKeys, Limit)
+        , select/1    %% (Cont)
+        , fold/5      %% (Ref, Fun, Acc, MatchSpec, Limit)
+        , rdb_fold/5  %% (Ref, Fun, Acc, Prefix, Limit)
+        ]).
+
+-export([continuation_info/2]).
+
+-import(mnesia_rocksdb_lib, [ keypos/1
+                            , decode_key/2
+                            , decode_val/3
+                            ]).
+
+-include("mnesia_rocksdb.hrl").
+
+-record(sel, { alias                            % TODO: not used
+             , tab
+             , ref
+             , keypat
+             , ms                               % TODO: not used
+             , compiled_ms
+             , limit
+             , key_only = false                 % TODO: not used
+             , direction = forward              % TODO: not used
+             }).
+
+select(Ref, MS, Limit) when is_map(Ref), is_list(MS) ->
+    select(Ref, MS, false, Limit).
+
+select(Ref, MS, AccKeys, Limit)
+  when is_map(Ref), is_list(MS), is_boolean(AccKeys) ->
+    Sel = mk_sel(Ref, MS, Limit),
+    mrdb:with_rdb_iterator(Ref, fun(I) -> i_select(I, Sel, AccKeys, []) end).
+
+mk_sel(#{name := Tab} = Ref, MS, Limit) ->
+    Keypat = keypat(MS, keypos(Tab), Ref),
+    #sel{tab = Tab,
+         ref = Ref,
+         keypat = Keypat,
+         ms = MS,
+         compiled_ms = ets:match_spec_compile(MS),
+         key_only = needs_key_only(MS),
+         limit = Limit}.
+
+select(Cont) ->
+    case Cont of
+        '$end_of_table' -> '$end_of_table';
+        _ when is_function(Cont, 1) ->
+            Cont(cont)
+    end.
+
+continuation_info(Item, C) when is_atom(Item), is_function(C, 1) ->
+    continuation_info_(Item, C(sel));
+continuation_info(_, _) -> undefined.
+
+continuation_info_(ref,       #sel{ref       = Ref}) -> Ref;
+continuation_info_(ms,        #sel{ms        = MS }) -> MS;
+continuation_info_(limit,     #sel{limit     = L  }) -> L;
+continuation_info_(direction, #sel{direction = Dir}) -> Dir;
+continuation_info_(_, _) -> undefined.
+
+fold(Ref, Fun, Acc, MS, Limit) ->
+   {AccKeys, F} =
+        if is_function(Fun, 3) ->
+                {true, fun({K, Obj}, Acc1) ->
+                               Fun(Obj, K, Acc1)
+                       end};
+           is_function(Fun, 2) ->
+                {false, Fun};
+           true ->
+                mrdb:abort(invalid_fold_fun)
+        end,
+    fold_(select(Ref, MS, AccKeys, Limit), F, Acc).
+
+fold_('$end_of_table', _, Acc) ->
+    Acc;
+fold_(L, Fun, Acc) when is_list(L) ->
+    lists:foldl(Fun, Acc, L);
+fold_({L, Cont}, Fun, Acc) ->
+    fold_(select(Cont), Fun, lists:foldl(Fun, Acc, L)).
+
+rdb_fold(Ref, Fun, Acc, Prefix, Limit) ->
+    mrdb:with_rdb_iterator(
+      Ref, fun(I) ->
+                   MovRes = rocksdb:iterator_move(I, first(Ref)),
+                   i_rdb_fold(MovRes, I, Prefix, Fun, Acc, Limit)
+           end).
+
+first(#{vsn := 1}) -> <<?DATA_START>>;
+first(_) -> first.
+
+i_rdb_fold({ok, K, V}, I, Pfx, Fun, Acc, Limit) when Limit > 0 ->
+    case is_prefix(Pfx, K) of
+        true ->
+            i_rdb_fold(rocksdb:iterator_move(I, next), I, Pfx, Fun,
+                       Fun(K, V, Acc), decr(Limit));
+        false ->
+            Acc
+    end;
+i_rdb_fold(_, _, _, _, Acc, _) ->
+    Acc.
+
+i_select(I, #sel{ keypat = Pfx
+                , compiled_ms = MS
+                , limit = Limit
+                , ref = #{vsn := Vsn, encoding := Enc} } = Sel, AccKeys, Acc) ->
+    StartKey = case {Pfx, Vsn, Enc}  of
+                   {<<>>, 1, {sext, _}} ->
+                       <<?DATA_START>>;
+                   {_, _, {term, _}} ->
+                       <<>>;
+                   _ ->
+                       Pfx
+               end,
+    select_traverse(rocksdb:iterator_move(I, StartKey), Limit,
+                    Pfx, MS, I, Sel, AccKeys, Acc).
+
+needs_key_only([Pat]) ->
+    needs_key_only_(Pat);
+needs_key_only([_|_] = Pats) ->
+    lists:all(fun needs_key_only_/1, Pats).
+
+needs_key_only_({HP, _, Body}) ->
+    BodyVars = lists:flatmap(fun extract_vars/1, Body),
+    %% Note that we express the conditions for "needs more than key" and negate.
+    not(wild_in_body(BodyVars) orelse
+        case bound_in_headpat(HP) of
+            {all,V} -> lists:member(V, BodyVars);
+            Vars when is_list(Vars) -> any_in_body(lists:keydelete(2,1,Vars), BodyVars)
+        end).
+
+extract_vars([H|T]) ->
+    extract_vars(H) ++ extract_vars(T);
+extract_vars(T) when is_tuple(T) ->
+    extract_vars(tuple_to_list(T));
+extract_vars(T) when T=='$$'; T=='$_' ->
+    [T];
+extract_vars(T) when is_atom(T) ->
+    case is_wild(T) of
+        true ->
+            [T];
+        false ->
+            []
+    end;
+extract_vars(_) ->
+    [].
+
+any_in_body(Vars, BodyVars) ->
+    lists:any(fun({_,Vs}) ->
+                      intersection(Vs, BodyVars) =/= []
+              end, Vars).
+
+intersection(A,B) when is_list(A), is_list(B) ->
+    A -- (A -- B).
+
+is_wild('_') ->
+    true;
+is_wild(A) when is_atom(A) ->
+    case atom_to_list(A) of
+        "\$" ++ S ->
+            try begin
+                    _ = list_to_integer(S),
+                    true
+                end
+            catch
+                error:_ ->
+                    false
+            end;
+        _ ->
+            false
+    end.
+
+wild_in_body(BodyVars) ->
+    intersection(BodyVars, ['$$','$_']) =/= [].
+
+bound_in_headpat(HP) when is_atom(HP) ->
+    {all, HP};
+bound_in_headpat(HP) when is_tuple(HP) ->
+    [_|T] = tuple_to_list(HP),
+    map_vars(T, 2).
+
+map_vars([H|T], P) ->
+    case extract_vars(H) of
+        [] ->
+            map_vars(T, P+1);
+        Vs ->
+            [{P, Vs}|map_vars(T, P+1)]
+    end;
+map_vars([], _) ->
+    [].
+
+select_traverse({ok, K, V}, Limit, Pfx, MS, I, #sel{ref = R} = Sel,
+                AccKeys, Acc) ->
+    case is_prefix(Pfx, K) of
+        true ->
+            DecKey = decode_key(K, R),
+            Rec = decode_val(V, DecKey, R),
+            case ets:match_spec_run([Rec], MS) of
+                [] ->
+                    select_traverse(
+                      rocksdb:iterator_move(I, next), Limit, Pfx, MS,
+                      I, Sel, AccKeys, Acc);
+                [Match] ->
+                    Acc1 = if AccKeys ->
+                                  [{K, Match}|Acc];
+                              true ->
+                                  [Match|Acc]
+                           end,
+                    traverse_continue(K, decr(Limit), Pfx, MS, I, Sel, AccKeys, Acc1)
+            end;
+        false when Limit == infinity ->
+            lists:reverse(Acc);
+        false ->
+            {lists:reverse(Acc), '$end_of_table'}
+    end;
+select_traverse({error, _}, Limit, _, _, _, _, _, Acc) ->
+    select_return(Limit, {lists:reverse(Acc), '$end_of_table'}).
+
+select_return(infinity, {L, '$end_of_table'}) ->
+    L;
+select_return(_, Ret) ->
+    Ret.
+
+is_prefix(A, B) when is_binary(A), is_binary(B) ->
+    Sa = byte_size(A),
+    case B of
+        <<A:Sa/binary, _/binary>> ->
+            true;
+        _ ->
+            false
+    end.
+
+decr(I) when is_integer(I) ->
+    I-1;
+decr(infinity) ->
+    infinity.
+
+traverse_continue(K, 0, Pfx, MS, _I, #sel{limit = Limit, ref = Ref} = Sel, AccKeys, Acc) ->
+    {lists:reverse(Acc),
+     fun(sel) -> Sel;
+        (cont) ->
+             mrdb:with_rdb_iterator(
+               Ref,
+               fun(NewI) ->
+                       select_traverse(iterator_next(NewI, K),
+                                       Limit, Pfx, MS, NewI, Sel,
+                                       AccKeys, [])
+               end)
+     end};
+traverse_continue(_K, Limit, Pfx, MS, I, Sel, AccKeys, Acc) ->
+    select_traverse(rocksdb:iterator_move(I, next), Limit, Pfx, MS, I, Sel, AccKeys, Acc).
+
+iterator_next(I, K) ->
+    case rocksdb:iterator_move(I, K) of
+        {ok, K, _} ->
+            rocksdb:iterator_move(I, next);
+        Other ->
+            Other
+    end.
+
+keypat([H|T], KeyPos, Ref) ->
+    keypat(T, KeyPos, Ref, keypat_pfx(H, KeyPos, Ref)).
+
+keypat(_, _, _, <<>>) -> <<>>;
+keypat([H|T], KeyPos, Ref, Pfx0) ->
+    Pfx = keypat_pfx(H, KeyPos, Ref),
+    keypat(T, KeyPos, Ref, common_prefix(Pfx, Pfx0));
+keypat([], _, _, Pfx) ->
+    Pfx.
+
+common_prefix(<<H, T/binary>>, <<H, T1/binary>>) ->
+    <<H, (common_prefix(T, T1))/binary>>;
+common_prefix(_, _) ->
+    <<>>.
+
+keypat_pfx({HeadPat,_Gs,_}, KeyPos, #{encoding := {sext,_}}) when is_tuple(HeadPat) ->
+    KP      = element(KeyPos, HeadPat),
+    sext:prefix(KP);
+keypat_pfx(_, _, _) ->
+    <<>>.
+

test/mnesia_rocksdb_SUITE.erl

@@ -1,3 +1,4 @@
+%% -*- mode: erlang; erlang-indent-level: 4; indent-tabs-mode: nil -*-
 -module(mnesia_rocksdb_SUITE).
 
 -export([
@@ -12,10 +13,25 @@
         , end_per_testcase/2
         ]).
 
--export([error_handling/1]).
+-export([ encoding_sext_attrs/1
+        , encoding_binary_binary/1
+        , encoding_defaults/1
+        ]).
+-export([ mrdb_batch/1
+        , mrdb_transactions/1
+	, mrdb_abort_reasons/1
+        , mrdb_repeated_transactions/1
+        , mrdb_abort/1
+        , mrdb_two_procs/1
+        , mrdb_two_procs_tx_restart/1
+        , mrdb_two_procs_snap/1
+        , mrdb_three_procs/1
+        ]).
 
 -include_lib("common_test/include/ct.hrl").
 
+-define(TABS_CREATED, tables_created).
+
 suite() ->
     [].
 
@@ -23,18 +39,40 @@ all() ->
     [{group, all_tests}].
 
 groups() ->
-    [{all_tests, [sequence], [error_handling]}].
+    [
+      {all_tests, [sequence], [ {group, checks}
+                              , {group, mrdb} ]}
+                              %% , error_handling ]}
+    , {checks, [sequence], [ encoding_sext_attrs
+                           , encoding_binary_binary
+                           , encoding_defaults ]}
+    , {mrdb, [sequence], [ mrdb_batch
+                         , mrdb_transactions
+			 , mrdb_abort_reasons
+                         , mrdb_repeated_transactions
+                         , mrdb_abort
+                         , mrdb_two_procs
+                         , mrdb_two_procs_tx_restart
+                         , mrdb_two_procs_snap
+                         , mrdb_three_procs ]}
+    ].
 
 
-error_handling(_Config) ->
+%% error_handling(Config) ->
-    mnesia_rocksdb_error_handling:run().
+%%     mnesia_rocksdb_error_handling:run(Config).
 
 init_per_suite(Config) ->
-    Config.
+    tr_ct:set_activation_checkpoint(?TABS_CREATED, Config).
 
 end_per_suite(_Config) ->
     ok.
 
+init_per_group(G, Config) when G==mrdb
+                             ; G==checks ->
+    mnesia:stop(),
+    ok = mnesia_rocksdb_tlib:start_mnesia(reset),
+    Config;
+
 init_per_group(_, Config) ->
     Config.
 
@@ -46,3 +84,564 @@ init_per_testcase(_, Config) ->
 
 end_per_testcase(_, _Config) ->
     ok.
+
+encoding_sext_attrs(Config) ->
+    tr_ct:with_trace(fun encoding_sext_attrs_/1, Config,
+                     tr_patterns(mnesia_rocksdb,
+                                 [{mnesia_rocksdb,'_',x}], tr_opts())).
+
+encoding_sext_attrs_(Config) ->
+    Created = create_tabs([{t, [{attributes, [k, v]}]}], Config),
+    ok = mrdb:insert(t, {t, 1, a}),
+    ok = mnesia:dirty_write({t, 2, b}),
+    expect_error(fun() -> mrdb:insert(t, {t, a}) end, ?LINE,
+                 error, {mrdb_abort, badarg}),
+    expect_error(fun() -> mnesia:dirty_write({t, a}) end, ?LINE,
+                 exit, '_'),
+    delete_tabs(Created),
+    ok.
+
+encoding_defaults(Config) ->
+    UP = fun(T) -> mnesia:table_info(T, user_properties) end,
+    Created = create_tabs([ {a, [ {attributes, [k, v]}
+                                , {type, set}]}
+                          , {b, [ {attributes, [k, v, w]}
+                                , {type, ordered_set}]}
+                          , {c, [ {attributes, [k, v]}
+                                , {type, bag} ]}], Config),
+    [{mrdb_encoding,{term,{value,term}}}]  = UP(a),
+    [{mrdb_encoding,{sext,{object,term}}}] = UP(b),
+    [{mrdb_encoding,{sext,{value,term}}}]  = UP(c),
+    delete_tabs(Created),
+    ok.
+
+encoding_binary_binary(Config) ->
+    Created = create_tabs([ {a, [ {attributes, [k,v]}
+                                  , {user_properties,
+                                     [{mrdb_encoding, {raw, raw}}]}]}
+                          , {b, [ {attributes, [k, v, w]}
+                                , {user_properties,
+                                   [{mrdb_encoding, {raw, {object, term}}}]}]}
+                          ], Config),
+    expect_error(fun() ->
+                         create_tab(
+                           c, [ {attributes, [k, v, w]}
+                              , {user_properties,
+                                 [{mrdb_encoding, {raw, {value, raw}}}]}])
+                 end, ?LINE, error, '_'),
+    delete_tabs(Created),
+    ok.
+
+expect_error(F, Line, Type, Expected) ->
+    try F() of
+        Unexpected -> error({unexpected, Line, Unexpected})
+    catch
+        Type:Expected ->
+            ct:log("Caught expected ~p:~p (Line: ~p)", [Type, Expected, Line]),
+            ok;
+        Type:Error when Expected == '_' ->
+            ct:log("Caught expected ~p:_ (Line:~p): ~p", [Type, Line, Error]),
+            ok
+    end.
+
+mrdb_batch(Config) ->
+    Created = create_tabs([{b, []}], Config),
+    D0 = get_dict(),
+    mrdb:activity(
+      batch, rdb,
+      fun() ->
+              [mrdb:insert(b, {b, K, K})
+               || K <- lists:seq(1, 10)]
+      end),
+    dictionary_unchanged(D0),
+    [[{b,K,K}] = mrdb:read(b, K) || K <- lists:seq(1, 10)],
+    expect_error(
+      fun() -> mrdb:activity(
+                 batch, rdb,
+                 fun() ->
+                         mrdb:insert(b, {b, 11, 11}),
+                         error(willful_abort)
+                 end)
+      end, ?LINE, error, '_'),
+    dictionary_unchanged(D0),
+    [] = mrdb:read(b, 11),
+    TRef = mrdb:get_ref(b),
+    mrdb:activity(
+      batch, rdb,
+      fun() ->
+              mrdb:insert(TRef, {b, 12, 12})
+      end),
+    dictionary_unchanged(D0),
+    [{b, 12, 12}] = mrdb:read(b, 12),
+    mrdb:as_batch(b, fun(R) ->
+                             mrdb:insert(R, {b, 13, 13})
+                     end),
+    dictionary_unchanged(D0),
+    [{b, 13, 13}] = mrdb:read(b, 13),
+    delete_tabs(Created),
+    ok.
+
+mrdb_transactions(Config) ->
+    tr_ct:with_trace(fun mrdb_transactions_/1, Config,
+                     tr_patterns(
+                       mnesia_rocksdb_admin,
+                       [{mnesia_rocksdb_admin,'_',x}], tr_opts())).
+
+mrdb_transactions_(Config) ->
+    Created = create_tabs([{tx, []}], Config),
+    mrdb:insert(tx, {tx, a, 1}),
+    [_] = mrdb:read(tx, a),
+    D0 = get_dict(),
+    mrdb:activity(
+      tx, rdb,
+      fun() ->
+              [{tx,a,N}] = mrdb:read(tx, a),
+              N1 = N+1,
+              ok = mrdb:insert(tx, {tx,a,N1}),
+              [{tx,a,N1}] = mrdb:read(tx, a),
+              ok
+      end),
+    dictionary_unchanged(D0),
+    [{tx,a,2}] = mrdb:read(tx,a),
+    delete_tabs(Created),
+    ok.
+
+mrdb_abort_reasons(_Config) ->
+    Prev = mnesia_rocksdb_admin:set_and_cache_env(mnesia_compatible_aborts, true),
+    X = some_value,
+    compare_txs('throw', fun() -> throw(X) end),
+    compare_txs('exit' , fun() -> exit(X) end),
+    compare_txs('error', fun() -> error(X) end),
+    compare_txs('abort', fun() -> mnesia:abort(X) end),
+    compare_txs('abort' , fun() -> mrdb:abort(X) end),
+    mnesia_rocksdb_admin:set_and_cache_env(mnesia_compatible_aborts, Prev),
+    ok.
+
+compare_txs(Type, F) ->
+    {caught, exit, {aborted, EMn}} = mnesia_tx(F),
+    {caught, exit, {aborted, EMr}} = mrdb_tx(F),
+    ct:log("Mnesia = ~p/~p", [Type, EMn]),
+    ct:log("Mrdb   = ~p/~p", [Type, EMr]),
+    case {Type, EMn, EMr} of
+	{error, {some_value, [_|_]}, {some_value, []}} -> ok;
+	{throw, {throw, some_value}, {throw, some_value}} -> ok;
+	{exit, some_value, some_value} -> ok;
+	{abort, some_value, some_value} -> ok
+    end.
+
+mnesia_tx(F) ->
+    try
+	mnesia:activity(transaction, F)
+    catch
+	C:E ->
+	    {caught, C, E}
+    end.
+
+mrdb_tx(F) ->
+    try
+	mrdb:activity(transaction, rdb, F)
+    catch
+	C:E ->
+	    {caught, C, E}
+    end.
+
+mrdb_repeated_transactions(Config) ->
+    Created = create_tabs([{rtx, []}], Config),
+    mrdb:insert(rtx, {rtx, a, 0}),
+    [_] = mrdb:read(rtx, a),
+    Fun = fun() ->
+                  [{rtx, a, N}] = mrdb:read(rtx, a),
+                  N1 = N+1,
+                  ok = mrdb:insert(rtx, {rtx, a, N1})
+          end,
+    D0 = get_dict(),
+    [ok = mrdb:activity(tx, rdb, Fun) || _ <- lists:seq(1,100)],
+    dictionary_unchanged(D0),
+    [{rtx,a,100}] = mrdb:read(rtx, a),
+    delete_tabs(Created),
+    ok.
+
+mrdb_abort(Config) ->
+    Created = create_tabs([{tx_abort, []}], Config),
+    mrdb:insert(tx_abort, {tx_abort, a, 1}),
+    Pre = mrdb:read(tx_abort, a),
+    D0 = get_dict(),
+    TRes = try mrdb:activity(
+                 tx, rdb,
+                 fun() ->
+                         [{tx_abort, a, N}] = mrdb:read(tx_abort, a),
+                         error(abort_here),
+                         ok = mrdb:insert(tx_abort, [{tx_abort, a, N+1}]),
+                         noooo
+                 end)
+           catch
+               error:abort_here ->
+                   ok
+           end,
+    dictionary_unchanged(D0),
+    ok = TRes,
+    Pre = mrdb:read(tx_abort, a),
+    delete_tabs(Created),
+    ok.
+
+mrdb_two_procs(Config) ->
+    tr_ct:with_trace(fun mrdb_two_procs_/1, Config,
+                     tr_flags(
+                       {self(), [call, sos, p]},
+                       tr_patterns(
+                         mrdb, [ {mrdb, insert, 2, x}
+                               , {mrdb, read, 2, x}
+                               , {mrdb, activity, x}], tr_opts()))).
+
+mrdb_two_procs_(Config) ->
+    R = ?FUNCTION_NAME,
+    Parent = self(),
+    Created = create_tabs([{R, []}], Config),
+    mrdb:insert(R, {R, a, 1}),
+    Pre = mrdb:read(R, a),
+    F0 = fun() ->
+                 wait_for_other(Parent, ?LINE),
+                 ok = mrdb:insert(R, {R, a, 17}),
+                 wait_for_other(Parent, ?LINE)
+         end,
+    {POther, MRef} = spawn_opt(
+                       fun() ->
+                               D0 = get_dict(),
+                               ok = mrdb:activity(tx, rdb, F0),
+                               dictionary_unchanged(D0)
+                       end, [monitor]),
+    F1 = fun() ->
+                 Pre = mrdb:read(R, a),
+                 go_ahead_other(POther),
+                 await_other_down(POther, MRef, ?LINE),
+                 [{R, a, 17}] = mrdb:read(R, a),
+                 ok = mrdb:insert(R, {R, a, 18})
+         end,
+    go_ahead_other(1, POther),
+    Do0 = get_dict(),
+    try mrdb:activity({tx, #{no_snapshot => true,
+                             retries => 0}}, rdb, F1) of
+        ok -> error(unexpected)
+    catch
+        error:{error, "Resource busy" ++ _} ->
+            ok
+    end,
+    dictionary_unchanged(Do0),
+    [{R, a, 17}] = mrdb:read(R, a),
+    delete_tabs(Created),
+    ok.
+
+mrdb_two_procs_tx_restart(Config) ->
+    tr_ct:with_trace(fun mrdb_two_procs_tx_restart_/1, Config,
+                     light_tr_opts()).
+
+mrdb_two_procs_tx_restart_(Config) ->
+    R = ?FUNCTION_NAME,
+    Parent = self(),
+    Created = create_tabs([{R, []}], Config),
+    mrdb:insert(R, {R, a, 1}),
+    Pre = mrdb:read(R, a),
+    F0 = fun() ->
+                 wait_for_other(Parent, ?LINE),
+                 ok = mrdb:insert(R, {R, a, 17}),
+                 wait_for_other(Parent, ?LINE)
+         end,
+    {POther, MRef} = spawn_opt(
+                       fun() ->
+                               ok = mrdb:activity(tx, rdb, F0)
+                       end, [monitor]),
+    F1 = fun() ->
+                 OtherWrite = [{R, a, 17}],
+                 Att = get_attempt(),
+                 Expected = case Att of
+                                1 -> Pre;
+                                _ -> OtherWrite
+                            end,
+                 Expected = mrdb:read(R, a),
+                 go_ahead_other(POther),
+                 await_other_down(POther, MRef, ?LINE),
+                 OtherWrite = mrdb:read(R, a),
+                 ok = mrdb:insert(R, {R, a, 18})
+         end,
+    go_ahead_other(1, POther),
+    Do0 = get_dict(),
+    mrdb:activity({tx, #{no_snapshot => true}}, rdb, F1),
+    dictionary_unchanged(Do0),
+    [{R, a, 18}] = mrdb:read(R, a),
+    delete_tabs(Created),
+    ok.
+
+
+%
+%% For testing purposes, we use side-effects inside the transactions
+%% to synchronize the concurrent transactions. If a transaction fails due
+%% to "Resource busy", it can re-run, but then mustn't attempt to sync with
+%% the other transaction, which is already committed.
+%%
+%% To achieve this, we rely on the `mrdb:current_context()` function, which gives
+%% us information about which is the current attempt; we only sync on the first
+%% attempt, and ignore the sync ops on retries.
+%%
+-define(IF_FIRST(N, Expr),
+        if N == 1 ->
+                Expr;
+           true ->
+                ok
+        end).
+
+mrdb_two_procs_snap(Config) ->
+    %% _snap is now the default tx mode
+    R = ?FUNCTION_NAME,
+    Parent = self(),
+    Created = create_tabs([{R, []}], Config),
+    mrdb:insert(R, {R, a, 1}),
+    Pre = mrdb:read(R, a),
+    mrdb:insert(R, {R, b, 11}),
+    PreB = mrdb:read(R, b),
+    F0 = fun() ->
+                 ok = mrdb:insert(R, {R, a, 17}),
+                 wait_for_other(Parent, ?LINE)
+         end,
+    {POther, MRef} =
+        spawn_opt(fun() ->
+                          D0 = get_dict(),
+                          ok = mrdb:activity(tx, rdb, F0),
+                          dictionary_unchanged(D0)
+                  end, [monitor]),
+    F1 = fun() ->
+                 Att = get_attempt(),
+                 go_ahead_other(Att, POther),
+                 ARes = mrdb:read(R, a),
+                 ARes = case Att of
+                            1 -> Pre;
+                            2 -> [{R, a, 17}]
+                        end,
+                 await_other_down(POther, MRef, ?LINE),
+                 PreB = mrdb:read(R, b),
+                 mrdb:insert(R, {R, b, 18}),
+                 1477
+         end,
+    Do0 = get_dict(),
+    1477 = mrdb:activity(tx, rdb, F1),
+    dictionary_unchanged(Do0),
+    [{R, a, 17}] = mrdb:read(R, a),
+    [{R, b, 18}] = mrdb:read(R, b),
+    delete_tabs(Created),
+    ok.
+
+%% We spawn two helper processes, making it 3 transactions, with the one
+%% in the parent process. P2 writes to key `a`, which the other two try to read.
+%% We make sure that P2 commits before finishing the other two, and P3 and the 
+%% main thread sync, so as to maximize the contention for the retry lock.
+mrdb_three_procs(Config) ->
+    tr_ct:with_trace(fun mrdb_three_procs_/1, Config, light_tr_opts()).
+
+mrdb_three_procs_(Config) ->
+    R = ?FUNCTION_NAME,
+    Parent = self(),
+    Created = create_tabs([{R, []}], Config),
+    A0 = {R, a, 1},
+    A1 = {R, a, 11},
+    A2 = {R, a, 12},
+    ok = mrdb:insert(R, A0),
+    F1 = fun() ->
+                 ok = mrdb:insert(R, A1),
+                 ok = mrdb:insert(R, {R, p1, 1})
+         end,
+    {P1, MRef1} =
+        spawn_opt(fun() ->
+                          D0 = get_dict(),
+                          do_when_p_allows(
+                            1, Parent, ?LINE,
+                            fun() ->
+                                    ok = mrdb:activity({tx,#{retries => 0}}, rdb, F1)
+                            end),
+                          dictionary_unchanged(D0)
+                  end, [monitor]),
+    F2 = fun() ->
+                 [A0] = mrdb:read(R, a),
+                 Att = get_attempt(),
+                 wait_for_other(Att, Parent, ?LINE),
+                 do_when_p_allows(
+                   Att, Parent, ?LINE,
+                   fun() ->
+                           [A1] = mrdb:read(R, a),
+                           ok = mrdb:insert(R, A2),
+                           ok = mrdb:insert(R, {R, p2, 1})
+                   end)
+         end,
+    {P2, MRef2} =
+        spawn_opt(fun() ->
+                          D0 = get_dict(),
+                          try mrdb:activity(
+                                {tx, #{retries => 0,
+                                       no_snapshot => true}}, rdb, F2) of
+                              ok -> error(unexpected)
+                          catch
+                              error:{error, "Resource busy" ++ _} ->
+                                  ok
+                          end,
+                          dictionary_unchanged(D0)
+                  end, [monitor]),
+    Do0 = get_dict(),
+    ok = mrdb:activity(tx, rdb,
+                       fun() ->
+                               Att = get_attempt(),
+                               ARes = case Att of
+                                          1 -> [A0];
+                                          2 -> [A1]
+                                      end,
+                               %% First, ensure that P2 tx is running
+                               go_ahead_other(Att, P2),
+                               ARes = mrdb:read(R, a),
+                               allow_p(Att, P1, ?LINE),
+                               ARes = mrdb:read(R, a),
+                               allow_p(Att, P2, ?LINE),
+                               ARes = mrdb:read(R, a),
+                               await_other_down(P1, MRef1, ?LINE),
+                               await_other_down(P2, MRef2, ?LINE),
+                               ok = mrdb:insert(R, {R, p0, 1})
+                       end),
+    dictionary_unchanged(Do0),
+    [{R, p1, 1}] = mrdb:read(R, p1),
+    [] = mrdb:read(R, p2),
+    [A1] = mrdb:read(R, a),
+    [{R, p0, 1}] = mrdb:read(R, p0),
+    delete_tabs(Created),
+    ok.
+
+tr_opts() ->
+    #{patterns => [ {mrdb, '_', '_', x}
+                  , {mrdb_lib, '_', '_', x}
+                  , {tr_ttb, event, 3, []}
+                  , {?MODULE, go_ahead_other, 3, x}
+                  , {?MODULE, wait_for_other, 3, x}
+                  , {?MODULE, await_other_down, 3, x}
+                  , {?MODULE, do_when_p_allows, 4, x}
+                  , {?MODULE, allow_p, 3, x}
+                  ]}.
+
+light_tr_opts() ->
+    tr_flags(
+      {self(), [call, sos, p]},
+      tr_patterns(
+        mrdb, [ {mrdb, insert, 2, x}
+              , {mrdb, read, 2, x}
+              , {mrdb, activity, x} ], tr_opts())).
+
+tr_patterns(Mod, Ps, #{patterns := Pats} = Opts) ->
+    Pats1 = [P || P <- Pats, element(1,P) =/= Mod],
+    Opts#{patterns => Ps ++ Pats1}.
+
+tr_flags(Flags, Opts) when is_map(Opts) ->
+    Opts#{flags => Flags}.
+
+wait_for_other(Parent, L) ->
+    wait_for_other(get_attempt(), Parent, 1000, L).
+
+wait_for_other(Att, Parent, L) ->
+    wait_for_other(Att, Parent, 1000, L).
+
+wait_for_other(1, Parent, Timeout, L) ->
+    MRef = monitor(process, Parent),
+    Parent ! {self(), ready},
+    receive
+        {Parent, cont} ->
+            demonitor(MRef),
+            ok;
+        {'DOWN', MRef, _, _, Reason} ->
+            ct:log("Parent died, Reason = ~p", [Reason]),
+            exit(Reason)
+    after Timeout ->
+              demonitor(MRef),
+              error({inner_timeout, L})
+    end;
+wait_for_other(_, _, _, _) ->
+    ok.
+
+do_when_p_allows(Att, P, Line, F) ->
+    wait_for_other(Att, P, Line),
+    F(),
+    %% Tell P that we're done
+    go_ahead_other(Att, P, Line),
+    %% Wait for P to acknowlege
+    wait_for_other(Att, P, Line).
+
+allow_p(Att, P, Line) ->
+    go_ahead_other(Att, P),
+    %% This is where P does its thing.
+    wait_for_other(Att, P, Line),
+    %% Acknowledge
+    go_ahead_other(Att, P, Line).
+
+go_ahead_other(POther) ->
+    go_ahead_other(get_attempt(), POther).
+
+go_ahead_other(Att, POther) ->
+    go_ahead_other(Att, POther, 1000).
+
+go_ahead_other(Att, POther, Timeout) ->
+    ?IF_FIRST(Att, go_ahead_other_(POther, Timeout)).
+
+go_ahead_other_(POther, Timeout) ->
+    receive
+        {POther, ready} ->
+            POther ! {self(), cont}
+    after Timeout ->
+            error(go_ahead_timeout)
+    end.
+
+%% Due to transaction restarts, we may already have collected
+%% a DOWN message. In this case, P will already be dead, and there
+%% will not be a 'DOWN' messsage still in the msg queue.
+%% This is fine (we assume it is), and we just make sure that the
+%% process didn't die abnormally.
+await_other_down(P, MRef, Line) ->
+    Attempt = get_attempt(),
+    ?IF_FIRST(Attempt, await_other_down_(P, MRef, Line)).
+
+await_other_down_(P, MRef, Line) ->
+    receive {'DOWN', MRef, _, _, Reason} ->
+                case Reason of
+                    normal -> ok;
+                    _ ->
+                        error({abnormal_termination,
+                               [ {pid, P}
+                               , {mref, MRef}
+                               , {line, Line}
+                               , {reason, Reason}]})
+                end
+    after 1000 ->
+              error({monitor_timeout, Line})
+    end.
+
+get_attempt() ->
+    #{activity := #{attempt := Attempt}} = mrdb:current_context(),
+    Attempt.
+
+create_tabs(Tabs, Config) ->
+    Res = lists:map(fun create_tab/1, Tabs),
+    tr_ct:trace_checkpoint(?TABS_CREATED, Config),
+    Res.
+
+create_tab({T, Opts}) -> create_tab(T, Opts).
+
+create_tab(T, Opts) ->
+    {atomic, ok} = mnesia:create_table(T, [{rdb,[node()]} | Opts]),
+    T.
+
+delete_tabs(Tabs) ->
+    [{atomic,ok} = mnesia:delete_table(T) || T <- Tabs],
+    ok.
+
+get_dict() ->
+    {dictionary, D} = process_info(self(), dictionary),
+    [X || {K,_} = X <- D,
+          K =/= log_timestamp].
+
+dictionary_unchanged(Old) ->
+    New = get_dict(),
+    #{ deleted := []
+     , added   := [] } = #{ deleted => Old -- New
+                          , added   => New -- Old },
+    ok.

test/mnesia_rocksdb_error_handling.erl

@@ -1,116 +0,0 @@
--module(mnesia_rocksdb_error_handling).
-
--export([run/0,
-         run/4]).
-
-
-run() ->
-    setup(),
-    %% run only one test for 'fatal', to save time.
-    [run(Type, Op, L, MaintainSz) || MaintainSz <- [false, true],
-                                     Type <- [set, bag],
-                                     Op <- [insert, update, delete],
-                                     L <- levels()]
-        ++ [run(set, insert, fatal, false)].
-
-run(Type, Op, Level, MaintainSz) ->
-    setup(),
-    {ok, Tab} = create_tab(Type, Level, MaintainSz),
-    mnesia:dirty_write({Tab, a, 1}),                    % pre-existing data
-    with_mock(Level, Op, Tab, fun() ->
-                                      try_write(Op, Type, Tab),
-                                      expect_error(Level, Tab)
-                              end).
-
-levels() ->
-    [debug, verbose, warning, error].
-
-setup() ->
-    mnesia:stop(),
-    start_mnesia().
-
-create_tab(Type, Level, MaintainSz) ->
-    TabName = tab_name(Type, Level, MaintainSz),
-    %% create error store before the table
-    case ets:info(?MODULE) of
-        undefined ->
-            ?MODULE = ets:new(?MODULE, [bag, public, named_table]),
-            ok;
-        _ ->
-            ok
-    end,
-    UserProps = user_props(Level, MaintainSz),
-    {atomic, ok} = mnesia:create_table(TabName, [{rdb, [node()]},
-                                                 {user_properties, UserProps}]),
-    {ok, TabName}.
-
-tab_name(Type, Level, MaintainSz) ->
-    binary_to_atom(iolist_to_binary(
-                     ["t" | [["_", atom_to_list(A)]
-                                || A <- [?MODULE, Type, Level, MaintainSz]]]), utf8).
-
-user_props(Level, MaintainSz) ->
-    [{maintain_sz, MaintainSz},
-     {rocksdb_opts, [ {on_write_error, Level}
-                    , {on_write_error_store, ?MODULE} ]}].
-
-start_mnesia() ->
-    mnesia_rocksdb_tlib:start_mnesia(reset),
-    ok.
-
-with_mock(Level, Op, Tab, F) ->
-    mnesia:subscribe(system),
-    mnesia:set_debug_level(debug),
-    meck:new(mnesia_rocksdb_lib, [passthrough]),
-    meck:expect(mnesia_rocksdb_lib, put, 4, {error, some_put_error}),
-    meck:expect(mnesia_rocksdb_lib, write, 3, {error, some_write_error}),
-    meck:expect(mnesia_rocksdb_lib, delete, 3, {error,some_delete_error}),
-    try {Level, Op, Tab, F()} of
-        {_, _, _, ok} ->
-            ok;
-        Other ->
-            io:fwrite("OTHER: ~p~n", [Other]),
-            ok
-    catch
-        exit:{{aborted,_},_} ->
-            Level = error,
-            ok
-    after
-        mnesia:set_debug_level(none),
-        mnesia:unsubscribe(system),
-        meck:unload(mnesia_rocksdb_lib)
-    end.
-
-try_write(insert, set, Tab) ->
-    mnesia:dirty_write({Tab, b, 2});
-try_write(insert, bag, Tab) ->
-    mnesia:dirty_write({Tab, a, 2});
-try_write(update, _, Tab) ->
-    mnesia:dirty_write({Tab, a, 1});
-try_write(delete, _, Tab) ->
-    mnesia:dirty_delete({Tab, a}).
-
-
-expect_error(Level, Tab) ->
-    Tag = rpt_tag(Level),
-    receive
-        {mnesia_system_event, {mnesia_fatal, Fmt, Args, _Core}} ->
-            Tag = mnesia_fatal,
-            io:fwrite("EVENT(~p, ~p):~n  ~s", [Tag, Tab, io_lib:fwrite(Fmt, Args)]),
-            ok;
-        {mnesia_system_event, {Tag, Fmt, Args}} ->
-            io:fwrite("EVENT(~p, ~p):~n  ~s", [Tag, Tab, io_lib:fwrite(Fmt, Args)]),
-            ok
-    after 1000 ->
-            error({expected_error, [Level, Tab]})
-
-    end,
-    %% Also verify that an error entry has been written into the error store.
-    1 = ets:select_delete(?MODULE, [{{{Tab, '_'}, '_', '_'}, [], [true]}]),
-    ok.
-
-rpt_tag(fatal  ) -> mnesia_fatal;
-rpt_tag(error  ) -> mnesia_error;
-rpt_tag(warning) -> mnesia_warning;
-rpt_tag(verbose) -> mnesia_info;
-rpt_tag(debug  ) -> mnesia_info.

test/mnesia_rocksdb_fallback.erl

@@ -22,7 +22,7 @@
 
 -define(m(A,B), fun() -> L = ?LINE,
                          case {A,B} of
-                             {__X, __X} ->
+                             {X__, X__} ->
                                  B;
                              Other ->
                                  error({badmatch, [Other,

test/mnesia_rocksdb_indexes_SUITE.erl

@@ -16,13 +16,51 @@
 %% under the License.
 %%----------------------------------------------------------------
 
--module(mnesia_rocksdb_indexes).
+-module(mnesia_rocksdb_indexes_SUITE).
+
+-export([
+          all/0
+        , groups/0
+        , suite/0
+        , init_per_suite/1
+        , end_per_suite/1
+        , init_per_group/2
+        , end_per_group/2
+        , init_per_testcase/2
+        , end_per_testcase/2
+        ]).
+
+-export([
+          index_plugin_mgmt/1
+        , add_indexes/1
+        , create_bag_index/1
+        , create_ordered_index/1
+        , test_1_ram_copies/1
+        , test_1_disc_copies/1
+        , fail_1_disc_only/1
+        , plugin_ram_copies1/1
+        , plugin_ram_copies2/1
+        , plugin_disc_copies/1
+        , fail_plugin_disc_only/1
+        , plugin_disc_copies_bag/1
+        , plugin_rdb_ordered/1
+        , index_iterator/1
+        ]).
+
+-include_lib("common_test/include/ct.hrl").
 
 -export([run/0,
+         run/1,
          r1/0]).
 
+-define(TAB(T), list_to_atom(lists:flatten(io_lib:fwrite("~w_~w", [T, ?LINE])))).
+
 run() ->
+    run([]).
+
+run(Config) ->
     mnesia:stop(),
+    maybe_set_dir(Config),
     ok = mnesia_rocksdb_tlib:start_mnesia(reset),
     test(1, ram_copies, r1),
     test(1, disc_copies, d1),
@@ -33,15 +71,86 @@ run() ->
     add_del_indexes(),
     {atomic,ok} = mnesia_schema:add_index_plugin(
                     {pfx},mnesia_rocksdb, ix_prefixes),
-    test_index_plugin(pr1, ram_copies, ordered),
+    test_index_plugin(cfg([pr1, ram_copies, ordered], Config)),
-    test_index_plugin(pr2, ram_copies, bag),
+    test_index_plugin(cfg([pr2, ram_copies, bag], Config)),
-    test_index_plugin(pd1, disc_copies, ordered),
+    test_index_plugin(cfg([pd1, disc_copies, ordered], Config)),
-    fail(test_index_plugin, [pd2, disc_only_copies, ordered]),
+    fail(test_index_plugin, [cfg([pd2, disc_only_copies, ordered], Config)]),
-    test_index_plugin(pd2, disc_copies, bag),
+    test_index_plugin(cfg([pd2, disc_copies, bag], Config)),
-    test_index_plugin(pl2, rdb, ordered),
+    test_index_plugin(cfg([pl2, rdb, ordered], Config)),
-    test_index_plugin_mgmt(),
+    index_plugin_mgmt(Config),
     ok.
 
+suite() ->
+    [].
+
+all() ->
+    [{group, all_tests}].
+
+groups() ->
+    [
+      {all_tests, [sequence], [ {group, mgmt}, {group, access}, {group, plugin} ]}
+    , {mgmt, [sequence], [
+                           create_bag_index
+                         , create_ordered_index
+                         , index_plugin_mgmt
+                         , add_indexes
+                         ]}
+    , {access, [sequence], [
+                             test_1_ram_copies
+                           , test_1_disc_copies
+                           , fail_1_disc_only
+                           , index_iterator
+                           ]}
+    , {plugin, [sequence], [
+                             plugin_ram_copies1
+                           , plugin_ram_copies2
+                           , plugin_disc_copies
+                           , fail_plugin_disc_only
+                           , plugin_disc_copies_bag
+                           , plugin_rdb_ordered
+                           ]}
+    ].
+
+%% ======================================================================
+
+init_per_suite(Config) ->
+    mnesia:stop(),
+    maybe_set_dir(Config),
+    Config.
+
+end_per_suite(_) ->
+    ok.
+
+init_per_group(Grp, Config) ->
+    mnesia_rocksdb_tlib:restart_reset_mnesia(),
+    case Grp of
+        plugin ->
+            {atomic,ok} = mnesia_schema:add_index_plugin(
+                            {pfx},mnesia_rocksdb, ix_prefixes);
+        _ ->
+            ok
+    end,
+    Config.
+
+end_per_group(_, _) ->
+    ok.
+
+init_per_testcase(_, Config) ->
+    Config.
+
+end_per_testcase(_, _) ->
+    ok.
+
+%% ======================================================================
+
+cfg([Tab, Type, IxType], Config) ->
+    [{my_config, #{tab => Tab, type => Type, ixtype => IxType}} | Config];
+cfg(Cfg, Config) when is_map(Cfg) -> [{my_config, Cfg} | Config].
+
+cfg(Config) -> ?config(my_config, Config).
+
+%% ======================================================================
+
 r1() ->
     mnesia:stop(),
     ok = mnesia_rocksdb_tlib:start_mnesia(reset),
@@ -51,17 +160,28 @@ r1() ->
     dbg:tpl(mnesia_schema,x),
     dbg:tpl(mnesia_index,x),
     dbg:p(all,[c]),
-    test_index_plugin(pd2, disc_only_copies, ordered).
+    test_index_plugin(cfg([pd2, disc_only_copies, ordered], [])).
 
 fail(F, Args) ->
     try apply(?MODULE, F, Args),
          error(should_fail)
     catch
-        error:_ ->
+        error:R when R =/= should_fail ->
             io:fwrite("apply(~p, ~p, ~p) -> fails as expected~n",
                       [?MODULE, F, Args])
     end.
 
+test_1_ram_copies( _Cfg) -> test(1, ram_copies, r1).
+test_1_disc_copies(_Cfg) -> test(1, disc_copies, d1).
+fail_1_disc_only(  _Cfg) -> fail(test, [1, disc_only_copies, do1]).
+
+plugin_ram_copies1(Cfg) -> test_index_plugin(cfg([pr1, ram_copies, ordered], Cfg)).
+plugin_ram_copies2(Cfg) -> test_index_plugin(cfg([pr2, ram_copies, bag], Cfg)).
+plugin_disc_copies(Cfg) -> test_index_plugin(cfg([pd1, disc_copies, ordered], Cfg)).
+fail_plugin_disc_only(Cfg) -> fail(test_index_plugin, [cfg([pd2, disc_only_copies, ordered], Cfg)]).
+plugin_disc_copies_bag(Cfg) -> test_index_plugin(cfg([pd2, disc_copies, bag], Cfg)).
+plugin_rdb_ordered(Cfg) -> test_index_plugin(cfg([pl2, rdb, ordered], Cfg)).
+
 test(N, Type, T) ->
     {atomic, ok} = mnesia:create_table(T, [{Type,[node()]},
                                            {attributes,[k,a,b,c]},
@@ -81,7 +201,8 @@ add_del_indexes() ->
     {atomic, ok} = mnesia:add_table_index(l1, a),
     io:fwrite("add_del_indexes() -> ok~n", []).
 
-test_index_plugin(Tab, Type, IxType) ->
+test_index_plugin(Config) ->
+    #{tab := Tab, type := Type, ixtype := IxType} = cfg(Config),
     {atomic, ok} = mnesia:create_table(Tab, [{Type, [node()]},
                                              {index, [{{pfx}, IxType}]}]),
     mnesia:dirty_write({Tab, "foobar", "sentence"}),
@@ -100,10 +221,25 @@ test_index_plugin(Tab, Type, IxType) ->
             Res2 = lists:sort(mnesia:dirty_index_read(Tab,<<"whi">>, {pfx})),
             [{Tab,"foobar","sentence"}] = mnesia:dirty_index_read(
                                             Tab, <<"foo">>, {pfx})
-    end,
+    end.
-    io:fwrite("test_index_plugin(~p, ~p, ~p) -> ok~n", [Tab,Type,IxType]).
 
-test_index_plugin_mgmt() ->
+create_bag_index(_Config) ->
+    {aborted, {combine_error, _, _}} =
+        mnesia:create_table(bi, [{rdb, [node()]}, {index, [{val, bag}]}]),
+    ok.
+
+create_ordered_index(_Config) ->
+    {atomic, ok} =
+        mnesia:create_table(oi, [{rdb, [node()]}, {index, [{val, ordered}]}]),
+    ok.
+
+add_indexes(_Config) ->
+    T = ?TAB(t1),
+    {atomic, ok} = mnesia:create_table(T, [{rdb, [node()]}, {attributes, [k, a, b, c]}]),
+    {atomic, ok} = mnesia:add_table_index(T, a),
+    ok.
+
+index_plugin_mgmt(_Config) ->
     {aborted,_} = mnesia:create_table(x, [{index,[{unknown}]}]),
     {aborted,_} = mnesia:create_table(x, [{index,[{{unknown},bag}]}]),
     {aborted,_} = mnesia:create_table(x, [{index,[{{unknown},ordered}]}]),
@@ -166,9 +302,48 @@ test_index(3, T) ->
     io:fwrite("test_index(1, ~p) -> ok~n", [T]),
     ok.
 
+index_iterator(_Cfg) ->
+    T = ?TAB(it),
+    Attrs = [ {rdb,[node()]}
+            , {record_name, i}
+            , {attributes, [k,a,b]}
+            , {index, [a,b]} ],
+    {atomic, ok} = mnesia:create_table(T, Attrs),
+    ct:log("created tab T=~p: ~p", [T, Attrs]),
+    L1 = [{i,K,a,y} || K <- lists:seq(4,6)],
+    L2 = [{i,K,b,x} || K <- lists:seq(1,3)],
+    true = lists:all(fun(X) -> X == ok end,
+                     [mnesia:dirty_write(T, Obj) || Obj <- L1 ++ L2]),
+    ct:log("inserted ~p", [L1 ++ L2]),
+    ResA = [{a,X} || X <- L1] ++ [{b,Y} || Y <- L2],
+    ResB = [{x,X} || X <- L2] ++ [{y,Y} || Y <- L1],
+    F = fun iter_all/1,
+    ResA = mrdb_index:with_iterator(T, a, F),
+    ct:log("mrdb_index:with_iterator(T, a, F) -> ~p", [ResA]),
+    ResB = mrdb_index:with_iterator(T, b, F),
+    ct:log("mrdb_index:with_iterator(T, b, F) -> ~p", [ResB]),
+    ok.
+
+iter_all(I) ->
+    iter_all(mrdb_index:iterator_move(I, first), I).
+
+iter_all({ok, IxVal, Obj}, I) ->
+    [{IxVal, Obj} | iter_all(mrdb_index:iterator_move(I, next), I)];
+iter_all(_, _) ->
+    [].
+
 indexes(1) ->
     [a,{b,ordered},{c,bag}];
 indexes(2) ->
     [a,b,{c,bag}];
 indexes(3) ->
     [a,{b,ordered},{c,ordered}].
+
+maybe_set_dir(Config) ->
+    case proplists:get_value(priv_dir, Config) of
+        undefined ->
+            ok;
+        PDir ->
+            Dir = filename:join(PDir, "mnesia_indexes"),
+            application:set_env(mnesia, dir, Dir)
+    end.

test/mnesia_rocksdb_migration_SUITE.erl

@@ -0,0 +1,190 @@
+-module(mnesia_rocksdb_migration_SUITE).
+
+-export([
+         all/0
+       , suite/0
+       , groups/0
+       , init_per_suite/1
+       , end_per_suite/1
+       , init_per_group/2
+       , end_per_group/2
+       , init_per_testcase/2
+       , end_per_testcase/2
+        ]).
+
+-export([
+         manual_migration/1
+       , migrate_with_encoding_change/1
+       , auto_migration/1
+        ]).
+
+-include_lib("common_test/include/ct.hrl").
+
+-define(TABS_CREATED, tables_created).
+
+suite() ->
+    [].
+
+all() ->
+    [{group, all_tests}].
+
+groups() ->
+    [
+     {all_tests, [sequence], [ manual_migration
+                             , migrate_with_encoding_change ]}
+    ].
+
+init_per_suite(Config) ->
+    Config.
+
+end_per_suite(_Config) ->
+    ok.
+
+init_per_group(_, Config) ->
+    Config.
+
+end_per_group(_, _Config) ->
+    ok.
+
+init_per_testcase(_, Config) ->
+    mnesia:stop(),
+    ok = mnesia_rocksdb_tlib:start_mnesia(reset),
+    Config.
+%%    create_migrateable_db(Config).
+
+end_per_testcase(_, _Config) ->
+    ok.
+
+manual_migration(Config) ->
+    tr_ct:with_trace(fun manual_migration_/1, Config, tr_opts()).
+
+manual_migration_(Config) ->
+    create_migrateable_db(Config),
+    Tabs = tables(),
+    ct:log("Analyze (before): ~p", [analyze_tabs(Tabs)]),
+    Res = mnesia_rocksdb_admin:migrate_standalone(rdb, Tabs),
+    ct:log("migrate_standalone(rdb, ~p) -> ~p", [Tabs, Res]),
+    AnalyzeRes = analyze_tabs(Tabs),
+    ct:log("AnalyzeRes = ~p", [AnalyzeRes]),
+    MigRes = mnesia_rocksdb_admin:migrate_standalone(rdb, Tabs),
+    ct:log("MigRes = ~p", [MigRes]),
+    AnalyzeRes2 = analyze_tabs(Tabs),
+    ct:log("AnalyzeRes2 = ~p", [AnalyzeRes2]),
+    ct:log("Admin State = ~p", [sys:get_state(mnesia_rocksdb_admin)]),
+    ok.
+
+migrate_with_encoding_change(_Config) ->
+    ok = create_tab(t, [{user_properties, [{mrdb_encoding, {sext,{object,term}}},
+                                           {rocksdb_standalone, true}]},
+                        {index,[val]}
+                       ]),
+    mrdb:insert(t, {t, <<"1">>, <<"a">>}),
+    mrdb:insert(t, {t, <<"2">>, <<"b">>}),
+    TRef = mrdb:get_ref(t),
+    {ok, V1} = mrdb:rdb_get(TRef, sext:encode(<<"1">>), []),
+    {ok, V2} = mrdb:rdb_get(TRef, sext:encode(<<"2">>), []),
+    {t,[],<<"a">>} = binary_to_term(V1),
+    {t,[],<<"b">>} = binary_to_term(V2),
+    Opts = #{encoding => {raw, raw}},
+    MigRes = mnesia_rocksdb_admin:migrate_standalone(rdb, [{t, Opts}]),
+    ct:log("MigRes (t) = ~p", [MigRes]),
+    %%
+    %% Ensure that metadata reflect the migrated table
+    %% (now a column family, and the rocksdb_standalone prop gone)
+    %%
+    TRef1 = mrdb:get_ref(t),
+    ct:log("TRef1(t) = ~p", [TRef1]),
+    #{type := column_family,
+      properties := #{user_properties := UPs}} = TRef1,
+    error = maps:find(rocksdb_standalone, UPs),
+    UPsR = lists:sort(maps:values(UPs)),
+    UPsM = lists:sort(mnesia:table_info(t, user_properties)),
+    {UPsR,UPsM} = {UPsM,UPsR},
+    ct:log("user properties (t): ~p", [UPsM]),
+    [{<<"2">>, <<"b">>},
+     {<<"1">>, <<"a">>}] = mrdb:rdb_fold(
+                             t, fun(K,V,A) -> [{K,V}|A] end, [], <<>>),
+    ct:log("All data present in new column family", []),
+    ct:log("Contents of mnesia dir: ~p",
+           [ok(file:list_dir(mnesia:system_info(directory)))]),
+    ct:log("mnesia stopped", []),
+    mnesia:stop(),
+    mnesia:start(),
+    ct:log("mnesia started", []),
+    mnesia:info(),
+    ok = mnesia:wait_for_tables([t], 3000),
+    ct:log("tables loaded", []),
+    [{t,<<"1">>,<<"a">>},
+     {t,<<"2">>,<<"b">>}] = mrdb:select(
+                              t, [{'_',[],['$_']}]),
+    [{<<"2">>,<<"b">>},
+     {<<"1">>,<<"a">>}] = mrdb:rdb_fold(
+                            t, fun(K,V,A) -> [{K,V}|A] end, [], <<>>),
+    ok.
+
+auto_migration(_Config) ->
+    ok.
+
+ok({ok, Value}) -> Value.
+
+tr_opts() ->
+    #{ patterns => [ {mnesia_rocksdb_admin, '_', []}
+                   , {mnesia_rocksdb_lib, '_', []}
+                   , {rocksdb, '_', x} | trace_exports(mrdb, x) ] }.
+
+trace_exports(M, Pat) ->
+    Fs = M:module_info(exports),
+    [{M, F, A, Pat} || {F, A} <- Fs].
+
+tables() ->
+    [a].
+
+create_migrateable_db(Config) ->
+    Os = [{user_properties, [{rocksdb_standalone, true}]}],
+    TabNames = tables(),
+    Tabs = [{T, Os} || T <- TabNames],
+    create_tabs(Tabs, Config),
+    verify_tabs_are_standalone(TabNames),
+    fill_tabs(TabNames),
+    Config.
+
+fill_tabs(Tabs) ->
+    lists:foreach(fun(Tab) ->
+                          [mrdb:insert(Tab, {Tab, X, a}) || X <- lists:seq(1,3)]
+                  end, Tabs).
+
+create_tabs(Tabs, Config) ->
+    Res = lists:map(fun create_tab/1, Tabs),
+    tr_ct:trace_checkpoint(?TABS_CREATED, Config),
+    Res.
+
+create_tab({T, Opts}) ->
+    create_tab(T, Opts).
+
+create_tab(T, Opts) ->
+    {atomic, ok} = mnesia:create_table(T, [{rdb, [node()]} | Opts]),
+    ok.
+
+verify_tabs_are_standalone(Tabs) ->
+    case analyze_tabs(Tabs) of
+        {_, []} ->
+            ok;
+        {[], NotSA} ->
+            error({not_standalone, NotSA})
+    end.
+
+analyze_tabs(Tabs) ->
+    Dir = mnesia:system_info(directory),
+    Files = filelib:wildcard(filename:join(Dir, "*-_tab.extrdb")),
+    ct:log("Files = ~p", [Files]),
+    TabNames = lists:map(
+                 fun(F) ->
+                         {match,[TStr]} =
+                            re:run(F, "^.+/([^/]+)-_tab\\.extrdb$",
+                                   [{capture, [1], list}]),
+                         list_to_existing_atom(TStr)
+                 end, Files),
+    ct:log("TabNames = ~p", [TabNames]),
+    NotSA = Tabs -- TabNames,
+    {TabNames -- NotSA, NotSA}.
+

test/mnesia_rocksdb_proper_semantics_test.erl

@@ -78,6 +78,18 @@ setup_mnesia() ->
     ok = mnesia:delete_schema([node()]),
     ok = mnesia:create_schema([node()]),
     ok = mnesia:start(),
+    %%
+    %% dbg:tracer(),
+    %% dbg:tpl(mnesia_rocksdb_admin, x),
+    %% dbg:tpl(mnesia_rocksdb,x),
+    %% dbg:ctpl(mnesia_rocksdb, check_definition_entry),
+    %% dbg:ctpl(mnesia_rocksdb, '-check_definition/4-fun-0-'),
+    %% dbg:tpl(mnesia_rocksdb_lib,x),
+    %% dbg:tp(mnesia,x),
+    %% dbg:tpl(mrdb,x),
+    %% dbg:tp(rocksdb,x),
+    %% dbg:p(all,[c]),
+    %%
     {ok, rocksdb_copies} = mnesia_rocksdb:register().
 
 setup() ->

test/mnesia_rocksdb_tlib.erl

@@ -20,23 +20,32 @@
 
 -export([start_mnesia/0,
          start_mnesia/1,
+         restart_reset_mnesia/0,
          create_table/1,
          create_table/3,
          trace/2]).
 
+restart_reset_mnesia() ->
+    mnesia:stop(),
+    start_mnesia(reset).
 
 start_mnesia() ->
     start_mnesia(false).
 
 start_mnesia(Mode) ->
     if Mode==reset ->
-            mnesia:delete_schema([node()]),
+            DRes = mnesia:delete_schema([node()]),
-            mnesia:create_schema([node()],
+            ct:log("Delete schema: ~p", [DRes]),
-                                 [{backend_types,
+            CRes = mnesia:create_schema([node()],
-                                   [{rdb,mnesia_rocksdb}]}]);
+                                        [{backend_types,
+                                          [{rdb,mnesia_rocksdb}]}]),
+            ct:log("Create schema: ~p", [CRes]);
        true -> ok
     end,
-    mnesia:start().
+    SRes = mnesia:start(),
+    ct:log("Mnesia start: ~p", [SRes]),
+    true = lists:member(rdb, mnesia_schema:backend_types()),
+    SRes.
 
 create_table(Backend) ->
     create_table(Backend, [k,v], [v]).

test/mrdb_bench.erl

@@ -0,0 +1,74 @@
+-module(mrdb_bench).
+
+-compile(export_all).
+
+init() ->
+    mnesia:delete_schema([node()]),
+    mnesia_rocksdb:create_schema([node()]),
+    mnesia:start(),
+    [mnesia:create_table(Name, [{Type, [node()]}, {record_name, r}])
+     || {Name, Type} <- tabs()],
+    ok.
+
+tabs() ->
+    [{rc, ram_copies},
+     {dc, disc_copies},
+     {do, disc_only_copies},
+     {rocks, rocksdb_copies},
+     {rdb, rocksdb_copies}].
+
+fill(N) ->
+    [{T, timer:tc(fun() -> fill_(T, N) end)} || {T,_} <- tabs()].
+
+fill_(_, 0) ->
+    ok;
+fill_(T, N) when N > 0 ->
+    write(T, {r, N, <<"1234567890">>}),
+    fill_(T, N-1).
+
+write(rdb, Obj) ->
+    mrdb:insert(rdb, Obj);
+write(T, Obj) ->
+    mnesia:dirty_write(T, Obj).
+
+
+fold() ->
+    [{T, timer:tc(fun() -> fold_(T) end)} || {T,_} <- tabs()].
+
+fold_(rdb) ->
+    mrdb:fold(rdb, fun(_, Acc) -> Acc end, ok);
+fold_(T) ->
+    mnesia:activity(
+      async_dirty,
+      fun() ->
+	      mnesia:foldl(fun(_, Acc) -> Acc end, ok, T)
+      end).
+				    
+tx(N) ->
+    [{T, timer:tc(fun() -> tx_(T, N) end)} || {T,_} <- tabs()].
+
+%% tx_(T, N) ->
+%% tx_(T, N, N, 10).
+
+tx_(_, 0) -> ok;
+tx_(T, N) when N > 0 ->
+    one_tx(T, N),
+    tx_(T, N-1).
+
+one_tx(rdb, N) ->
+    mrdb:activity(transaction, rocksdb_copies,
+		  fun() ->
+			  [{r, N, Str}] = mrdb:read(rdb, N),
+			  Str2 = <<Str/binary, "x">>,
+			  mrdb:insert(rdb, {r, N, Str2}),
+			  [{r, N, Str2}] = mrdb:read(rdb, N)
+		  end);
+one_tx(T, N) ->
+    mnesia:activity(transaction,
+		    fun() ->
+			    [{r, N, Str}] = mnesia:read(T, N),
+			    Str2 = <<Str/binary, "x">>,
+			    mnesia:write(T, {r, N, Str2}, write),
+			    [{r, N, Str2}] = mnesia:read(T, N)
+		    end).
+			   

test/mrdb_ttb.erl

@@ -0,0 +1,31 @@
+-module(mrdb_ttb).
+
+-export([ on_nodes/2
+        , stop/0
+        , stop_nofetch/0
+        , format/2
+        , format/3 ]).
+
+-export([ patterns/0
+        , flags/0 ]).
+
+on_nodes(Ns, File) ->
+    tr_ttb:on_nodes(Ns, File, ?MODULE).
+
+patterns() ->
+    mrdb:patterns().
+
+flags() ->
+    {all, call}.
+
+stop() ->
+    tr_ttb:stop().
+
+stop_nofetch() ->
+    tr_ttb:stop_nofetch().
+
+format(Dir, Out) ->
+    tr_ttb:format(Dir, Out).
+
+format(Dir, Out, Opts) ->
+    tr_ttb:format(Dir, Out, Opts).