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commit    87eb25535d0db49fec9b3ddb2f1c4dfd97c8805e
Author:   Peter Geoghegan <pg@bowt.ie>
Date:     Wed Jul 29 23:00:54 2020 +0000
First released in: 9.5.23, 9.6.19, 10.14, 11.9

    Backpatch tuplesort.c assertion.
    
    Backpatch an assertion (that was originally added to Postgres 12 by
    commit dd299df8189) that seems broadly useful.  The assertion can detect
    violations of the HOT invariant (i.e. no two index tuples can point to
    the same heap TID) when CREATE INDEX somehow incorrectly allows that to
    take place.
    
    For example, a IndexBuildHeapScan/heapam_index_build_range_scan bug
    might result in two tuples that both point to the same heap TID.  If
    these two tuples also happen to be duplicates, the assertion will fail.
    
    Discussion: https://postgr.es/m/CAH2-WzmBxu4o=pMsniur+bwHqCGCmV_AOLkuK6BuU7ngA6evqw@mail.gmail.com
    Backpatch: 9.5-11 only


 src/backend/utils/sort/tuplesort.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index 549baf4b4f6..f770b570eb6 100644
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -4076,6 +4076,9 @@ comparetup_index_btree(const SortTuple *a, const SortTuple *b,
 			return (pos1 < pos2) ? -1 : 1;
 	}
 
+	/* ItemPointer values should never be equal */
+	Assert(false);
+
 	return 0;
 }
 
@@ -4128,6 +4131,9 @@ comparetup_index_hash(const SortTuple *a, const SortTuple *b,
 			return (pos1 < pos2) ? -1 : 1;
 	}
 
+	/* ItemPointer values should never be equal */
+	Assert(false);
+
 	return 0;
 }
 


[parent: baecd2715b5c]