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Commit7da5159

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Fix incorrect presorted DISTINCT aggregate if condition
Here we fix a faulty "if" condition which failed to correctly handle twoor more consecutive NULL transition values when checking if the new valueis DISTINCT from the old value for presorted aggregates. Given a suitablynon-strict aggregate transition function, a byref aggregate could cause acrash due to calling the type's equality function and passing along a(Datum) 0 value to test for equality, the equality function would then tryto dereference that 0 Datum and segfault. For byval types, there'd havebeen no crash and the equality function would have seen that the two 0Datums matched, which (only by chance) meant the calling code would haveworked correctly.Here we ensure that we only call the equality function when neither ofthe input values are NULL.This code is all new as of1349d27, so no backpatch needed.Reported-by: Fujii MasaoDiscussion:https://postgr.es/m/860c6d6f-a3c5-3ae9-9da2-827177bede06@oss.nttdata.com
1 parent836c31b commit7da5159

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3 files changed

+15
-3
lines changed

3 files changed

+15
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lines changed

‎src/backend/executor/execExprInterp.c

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -4250,9 +4250,9 @@ ExecEvalPreOrderedDistinctSingle(AggState *aggstate, AggStatePerTrans pertrans)
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if (!pertrans->haslast||
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pertrans->lastisnull!=isnull||
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!DatumGetBool(FunctionCall2Coll(&pertrans->equalfnOne,
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pertrans->aggCollation,
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pertrans->lastdatum,value)))
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(!isnull&&!DatumGetBool(FunctionCall2Coll(&pertrans->equalfnOne,
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pertrans->aggCollation,
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pertrans->lastdatum,value))))
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{
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if (pertrans->haslast&& !pertrans->inputtypeByVal)
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pfree(DatumGetPointer(pertrans->lastdatum));

‎src/test/regress/expected/aggregates.out

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1506,6 +1506,14 @@ group by ten;
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-> Seq Scan on tenk1
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(5 rows)
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-- Ensure consecutive NULLs are properly treated as distinct from each other
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select array_agg(distinct val)
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from (select null as val from generate_series(1, 2));
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array_agg
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-----------
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{NULL}
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(1 row)
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-- Ensure no ordering is requested when enable_presorted_aggregate is off
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set enable_presorted_aggregate to off;
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explain (costs off)

‎src/test/regress/sql/aggregates.sql

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -567,6 +567,10 @@ select
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from tenk1
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group by ten;
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-- Ensure consecutive NULLs are properly treated as distinct from each other
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select array_agg(distinct val)
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from (selectnullas valfrom generate_series(1,2));
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-- Ensure no ordering is requested when enable_presorted_aggregate is off
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set enable_presorted_aggregate to off;
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explain (costs off)

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