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commit    3a5817695a8360011864c1834f8a90ffdfc7f840
Author:   David Rowley <drowley@postgresql.org>
Date:     Wed Sep 28 22:43:00 2022 +0000
First released in: 16.0, 15.0

    Restrict Datum sort optimization to byval types only
    
    91e9e89dc modified nodeSort.c so that it used datum sorts when the
    targetlist of the outer node contained only a single column.  That commit
    failed to recognise that the Datum returned by tuplesort_getdatum() must
    be pfree'd when the type is a byref type.  Ronan Dunklau did originally
    propose the patch with that restriction, but that, probably through my own
    fault, got lost during further development work.
    
    Due to the timing of this report (PG15 RC1 is almost out the door), let's
    just restrict the datum sort optimization to apply for byval types only.
    We might want to look harder into making this work for byref types in
    PG16.
    
    Reported-by: Önder Kalacı
    Diagnosis-by: Tom Lane
    Discussion: https://postgr.es/m/CACawEhVxe0ufR26UcqtU7GYGRuubq3p6ZWPGXL4cxy_uexpAAQ@mail.gmail.com
    Backpatch-through: 15, where 91e9e89dc was introduced.


 src/backend/executor/nodeSort.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/backend/executor/nodeSort.c b/src/backend/executor/nodeSort.c
index 3c28d60c3ef..37ad35704bc 100644
--- a/src/backend/executor/nodeSort.c
+++ b/src/backend/executor/nodeSort.c
@@ -220,6 +220,7 @@ SortState *
 ExecInitSort(Sort *node, EState *estate, int eflags)
 {
 	SortState  *sortstate;
+	TupleDesc	outerTupDesc;
 
 	SO1_printf("ExecInitSort: %s\n",
 			   "initializing sort node");
@@ -274,11 +275,13 @@ ExecInitSort(Sort *node, EState *estate, int eflags)
 	ExecInitResultTupleSlotTL(&sortstate->ss.ps, &TTSOpsMinimalTuple);
 	sortstate->ss.ps.ps_ProjInfo = NULL;
 
+	outerTupDesc = ExecGetResultType(outerPlanState(sortstate));
+
 	/*
-	 * We perform a Datum sort when we're sorting just a single column,
+	 * We perform a Datum sort when we're sorting just a single byval column,
 	 * otherwise we perform a tuple sort.
 	 */
-	if (ExecGetResultType(outerPlanState(sortstate))->natts == 1)
+	if (outerTupDesc->natts == 1 && TupleDescAttr(outerTupDesc, 0)->attbyval)
 		sortstate->datumSort = true;
 	else
 		sortstate->datumSort = false;


[parent: 2a66b9bfb74e]