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Fix sharing Agg transition state of DISTINCT or ordered aggs.

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If a query contained two aggregates that could share the transition value,
we would correctly collect the input into a tuplesort only once, but
incorrectly run the transition function over the accumulated input twice,
in finalize_aggregates(). That caused a crash, when we tried to call
tuplesort_performsort() on an already-freed NULL tuplestore.

Backport to 9.6, where sharing of transition state and this bug were
introduced.

Analysis by Tom Lane.

Discussion: https://www.postgresql.org/message-id/ac5b0b69-744c-9114-6218-8300ac920e61@iki.fi
This commit is contained in:
Heikki Linnakangas 2016-12-20 09:20:17 +02:00
parent 3f07eff104
commit ce92fc4e25
3 changed files with 30 additions and 3 deletions
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21
src/backend/executor/nodeAgg.c
View File

@ -1565,16 +1565,19 @@ finalize_aggregates(AggState *aggstate,
Datum *aggvalues = econtext->ecxt_aggvalues;
bool *aggnulls = econtext->ecxt_aggnulls;
int aggno;
int transno;
Assert(currentSet == 0 ||
((Agg *) aggstate->ss.ps.plan)->aggstrategy != AGG_HASHED);
aggstate->current_set = currentSet;
for (aggno = 0; aggno < aggstate->numaggs; aggno++)
/*
* If there were any DISTINCT and/or ORDER BY aggregates, sort their
* inputs and run the transition functions.
*/
for (transno = 0; transno < aggstate->numtrans; transno++)
{
AggStatePerAgg peragg = &peraggs[aggno];
int transno = peragg->transno;
AggStatePerTrans pertrans = &aggstate->pertrans[transno];
AggStatePerGroup pergroupstate;
@ -1593,6 +1596,18 @@ finalize_aggregates(AggState *aggstate,
pertrans,
pergroupstate);
}
}
/*
* Run the final functions.
*/
for (aggno = 0; aggno < aggstate->numaggs; aggno++)
{
AggStatePerAgg peragg = &peraggs[aggno];
int transno = peragg->transno;
AggStatePerGroup pergroupstate;
pergroupstate = &pergroup[transno + (currentSet * (aggstate->numtrans))];
if (DO_AGGSPLIT_SKIPFINAL(aggstate->aggsplit))
finalize_partialaggregate(aggstate, peragg, pergroupstate,

9
src/test/regress/expected/aggregates.out
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@ -1816,6 +1816,15 @@ NOTICE: avg_transfn called with 3
2 | 4
(1 row)
-- same as previous one, but with DISTINCT, which requires sorting the input.
select my_avg(distinct one),my_sum(distinct one) from (values(1),(3),(1)) t(one);
NOTICE: avg_transfn called with 1
NOTICE: avg_transfn called with 3
my_avg | my_sum
--------+--------
2 | 4
(1 row)
-- shouldn't share states due to the distinctness not matching.
select my_avg(distinct one),my_sum(one) from (values(1),(3)) t(one);
NOTICE: avg_transfn called with 1

3
src/test/regress/sql/aggregates.sql
View File

@ -727,6 +727,9 @@ select my_avg(one),my_avg(one) from (values(1),(3)) t(one);
-- aggregate state should be shared as transfn is the same for both aggs.
select my_avg(one),my_sum(one) from (values(1),(3)) t(one);
-- same as previous one, but with DISTINCT, which requires sorting the input.
select my_avg(distinct one),my_sum(distinct one) from (values(1),(3),(1)) t(one);
-- shouldn't share states due to the distinctness not matching.
select my_avg(distinct one),my_sum(one) from (values(1),(3)) t(one);