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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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2
src/backend/utils/adt/xml.c
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@ -3948,7 +3948,7 @@ xpath(PG_FUNCTION_ARGS)
ArrayType *namespaces = PG_GETARG_ARRAYTYPE_P(2);
ArrayBuildState *astate;
astate = initArrayResult(XMLOID, CurrentMemoryContext);
astate = initArrayResult(XMLOID, CurrentMemoryContext, true);
xpath_internal(xpath_expr_text, data, namespaces,
NULL, astate);
PG_RETURN_ARRAYTYPE_P(makeArrayResult(astate, CurrentMemoryContext));