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In array_agg(), don't create a new context for every group.

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Previously, each new array created a new memory context that started
out at 8kB. This is incredibly wasteful when there are lots of small
groups of just a few elements each.

Change initArrayResult() and friends to accept a "subcontext" argument
to indicate whether the caller wants the ArrayBuildState allocated in
a new subcontext or not. If not, it can no longer be released
separately from the rest of the memory context.

Fixes bug report by Frank van Vugt on 2013-10-19.

Tomas Vondra. Reviewed by Ali Akbar, Tom Lane, and me.
This commit is contained in:
Jeff Davis
2015-02-21 17:24:48 -08:00
parent e9fd5545de
commit b419865a81
6 changed files with 92 additions and 44 deletions
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14
src/backend/utils/adt/array_userfuncs.c
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@ -520,8 +520,13 @@ array_agg_transfn(PG_FUNCTION_ARGS)
elog(ERROR, "array_agg_transfn called in non-aggregate context");
}
state = PG_ARGISNULL(0) ? NULL : (ArrayBuildState *) PG_GETARG_POINTER(0);
if (PG_ARGISNULL(0))
state = initArrayResult(arg1_typeid, aggcontext, false);
else
state = (ArrayBuildState *) PG_GETARG_POINTER(0);
elem = PG_ARGISNULL(1) ? (Datum) 0 : PG_GETARG_DATUM(1);
state = accumArrayResult(state,
elem,
PG_ARGISNULL(1),
@ -595,7 +600,12 @@ array_agg_array_transfn(PG_FUNCTION_ARGS)
elog(ERROR, "array_agg_array_transfn called in non-aggregate context");
}
state = PG_ARGISNULL(0) ? NULL : (ArrayBuildStateArr *) PG_GETARG_POINTER(0);
if (PG_ARGISNULL(0))
state = initArrayResultArr(arg1_typeid, InvalidOid, aggcontext, false);
else
state = (ArrayBuildStateArr *) PG_GETARG_POINTER(0);
state = accumArrayResultArr(state,
PG_GETARG_DATUM(1),
PG_ARGISNULL(1),