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Extend ExecBuildAggTrans() to support a NULL pointer check.

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Optionally push a step to check for a NULL pointer to the pergroup
state.

This will be important for disk-based hash aggregation in combination
with grouping sets. When memory limits are reached, a given tuple may
find its per-group state for some grouping sets but not others. For
the former, it advances the per-group state as normal; for the latter,
it skips evaluation and the calling code will have to spill the tuple
and reprocess it in a later batch.

Add the NULL check as a separate expression step because in some
common cases it's not needed.

Discussion: https://postgr.es/m/20200221202212.ssb2qpmdgrnx52sj%40alap3.anarazel.de
This commit is contained in:
Jeff Davis
2020-03-04 17:20:20 -08:00
parent 3ed2005ff5
commit c954d49046
6 changed files with 101 additions and 7 deletions
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17
src/backend/executor/execExprInterp.c
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@ -435,6 +435,7 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
&&CASE_EEOP_AGG_DESERIALIZE,
&&CASE_EEOP_AGG_STRICT_INPUT_CHECK_ARGS,
&&CASE_EEOP_AGG_STRICT_INPUT_CHECK_NULLS,
&&CASE_EEOP_AGG_PLAIN_PERGROUP_NULLCHECK,
&&CASE_EEOP_AGG_PLAIN_TRANS_INIT_STRICT_BYVAL,
&&CASE_EEOP_AGG_PLAIN_TRANS_STRICT_BYVAL,
&&CASE_EEOP_AGG_PLAIN_TRANS_BYVAL,
@ -1603,6 +1604,22 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
EEO_NEXT();
}
/*
* Check for a NULL pointer to the per-group states.
*/
EEO_CASE(EEOP_AGG_PLAIN_PERGROUP_NULLCHECK)
{
AggState *aggstate = castNode(AggState, state->parent);
AggStatePerGroup pergroup_allaggs = aggstate->all_pergroups
[op->d.agg_plain_pergroup_nullcheck.setoff];
if (pergroup_allaggs == NULL)
EEO_JUMP(op->d.agg_plain_pergroup_nullcheck.jumpnull);
EEO_NEXT();
}
/*
* Different types of aggregate transition functions are implemented
* as different types of steps, to avoid incurring unnecessary