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On select, mnesia_rocksdb would only calculate a key prefix for the

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first select clause in a multi-clause select pattern. This could give
erroneous results if the first pattern was more specific (on the key)
than following patterns. This change calculates a prefix for all clauses
and keeps the shortest common prefix.
This commit is contained in:
Ulf Wiger 2018-02-16 18:43:59 +01:00
parent ff823c4ee1
commit 0345e3558b
1 changed files with 20 additions and 21 deletions
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41
src/mnesia_rocksdb.erl
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@ -1403,7 +1403,7 @@ do_select(Ref, Tab, _Type, MS, AccKeys, Limit) when is_boolean(AccKeys) ->
limit = Limit},
with_iterator(Ref, fun(I) -> i_do_select(I, Sel, AccKeys, []) end).
i_do_select(I, #sel{keypat = {Pfx, _KP},
i_do_select(I, #sel{keypat = Pfx,
compiled_ms = MS,
limit = Limit} = Sel, AccKeys, Acc) ->
StartKey =
@ -1534,27 +1534,26 @@ iterator_next(I, K) ->
Other
end.
keypat([{HeadPat,Gs,_}|_], KeyPos) when is_tuple(HeadPat) ->
KP = element(KeyPos, HeadPat),
KeyVars = extract_vars(KP),
Guards = relevant_guards(Gs, KeyVars),
Pfx = sext:prefix(KP),
{Pfx, [{KP, Guards, [true]}]};
keypat(_, _) ->
{<<>>, [{'_',[],[true]}]}.
keypat([H|T], KeyPos) ->
keypat(T, KeyPos, keypat_pfx(H, KeyPos)).
relevant_guards(Gs, Vars) ->
case Vars -- ['_'] of
[] ->
[];
Vars1 ->
Fun =
fun(G) ->
Vg = extract_vars(G),
intersection(Vg, Vars1) =/= [] andalso (Vg--Vars1) == []
end,
lists:filter(Fun, Gs)
end.
keypat(_, _, <<>>) -> <<>>;
keypat([H|T], KeyPos, Pfx0) ->
Pfx = keypat_pfx(H, KeyPos),
keypat(T, KeyPos, 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) when is_tuple(HeadPat) ->
KP = element(KeyPos, HeadPat),
sext:prefix(KP);
keypat_pfx(_, _) ->
<<>>.
%% ----------------------------------------------------------------------------
%% COMMON PRIVATE