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commit    5db9367e51136cb270feb79c741f68c1413dce78
Author:   David Rowley <drowley@postgresql.org>
Date:     Fri Jan 10 01:31:31 2025 +0000
First released in: 18.0, 17.3

    Fix UNION planner datatype issue
    
    66c0185a3 gave the planner the ability to have union child queries
    provide the union planner with pre-sorted input so that UNION queries
    could be more efficiently implemented using Merge Append.
    
    That commit overlooked checking that the UNION target list and the union
    child target list's types all match.  In some corner cases, this could
    result in the planner producing sorts using the sort operator of the
    top-level UNION's target list type rather than of the union child's
    target list's type.  The implications of this range from silently
    working correctly, despite using the wrong sort operator all the way up
    to a segmentation fault.
    
    Here we fix by adjusting the planner so it makes no attempt to have the
    subquery produce pre-sorted results when the data type of the UNION
    target list and the types from the subquery target list don't match
    exactly.
    
    Backpatch to 17, where 66c0185a3 was introduced.
    
    Reported-by: Jason Smith <dqetool@126.com>
    Diagnosed-by: Tom Lane <tgl@sss.pgh.pa.us>
    Bug: 18764
    Discussion: https://postgr.es/m/18764-63ad667ea26e877a%40postgresql.org
    Backpatch-through: 17


 src/backend/optimizer/plan/planner.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 39ade99155f..6eeeb0e1d03 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -8086,7 +8086,10 @@ group_by_has_partkey(RelOptInfo *input_rel,
  * child query's targetlist entries may already have a tleSortGroupRef
  * assigned for other purposes, such as GROUP BYs.  Here we keep the
  * SortGroupClause list in the same order as 'op' groupClauses and just adjust
- * the tleSortGroupRef to reference the TargetEntry's 'ressortgroupref'.
+ * the tleSortGroupRef to reference the TargetEntry's 'ressortgroupref'.  If
+ * any of the columns in the targetlist don't match to the setop's colTypes
+ * then we return an empty list.  This may leave some TLEs with unreferenced
+ * ressortgroupref markings, but that's harmless.
  */
 static List *
 generate_setop_child_grouplist(SetOperationStmt *op, List *targetlist)
@@ -8094,25 +8097,42 @@ generate_setop_child_grouplist(SetOperationStmt *op, List *targetlist)
 	List	   *grouplist = copyObject(op->groupClauses);
 	ListCell   *lg;
 	ListCell   *lt;
+	ListCell   *ct;
 
 	lg = list_head(grouplist);
+	ct = list_head(op->colTypes);
 	foreach(lt, targetlist)
 	{
 		TargetEntry *tle = (TargetEntry *) lfirst(lt);
 		SortGroupClause *sgc;
+		Oid			coltype;
 
 		/* resjunk columns could have sortgrouprefs.  Leave these alone */
 		if (tle->resjunk)
 			continue;
 
-		/* we expect every non-resjunk target to have a SortGroupClause */
+		/*
+		 * We expect every non-resjunk target to have a SortGroupClause and
+		 * colTypes.
+		 */
 		Assert(lg != NULL);
+		Assert(ct != NULL);
 		sgc = (SortGroupClause *) lfirst(lg);
+		coltype = lfirst_oid(ct);
+
+		/* reject if target type isn't the same as the setop target type */
+		if (coltype != exprType((Node *) tle->expr))
+			return NIL;
+
 		lg = lnext(grouplist, lg);
+		ct = lnext(op->colTypes, ct);
 
 		/* assign a tleSortGroupRef, or reuse the existing one */
 		sgc->tleSortGroupRef = assignSortGroupRef(tle, targetlist);
 	}
+
 	Assert(lg == NULL);
+	Assert(ct == NULL);
+
 	return grouplist;
 }


[parent: c559f61b5471]