Fix dependency handling at swap phase of REINDEX CONCURRENTLY

When swapping the dependencies of the old and new indexes, the code has
been correctly switching all links in pg_depend from the old to the new
index for both referencing and referenced entries.  However it forgot
the fact that the new index may itself have existing entries in
pg_depend, like references to the parent table attributes.  This
resulted in duplicated entries in pg_depend after running REINDEX
CONCURRENTLY.

Fix this problem by removing any existing entries in pg_depend for the
new index before switching the dependencies of the old index to the new
one.  More regression tests are added to check the consistency of
entries in pg_depend for indexes, including partitions.

Author: Michael Paquier
Discussion: https://postgr.es/m/20191025064318.GF8671@paquier.xyz
Backpatch-through: 12

1 files changed, 5 insertions, 1 deletions

diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 345628c42b9..2fe080863fe 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -1668,8 +1668,12 @@ index_concurrently_swap(Oid newIndexId, Oid oldIndexId, const char *oldName)
 	}
 
 	/*
-	 * Move all dependencies of and on the old index to the new one
+	 * Move all dependencies of and on the old index to the new one.  First
+	 * remove any dependencies that the new index may have to provide an
+	 * initial clean state for the dependency switch, and then move all the
+	 * dependencies from the old index to the new one.
 	 */
+	deleteDependencyRecordsFor(RelationRelationId, newIndexId, false);
 	changeDependenciesOf(RelationRelationId, oldIndexId, newIndexId);
 	changeDependenciesOn(RelationRelationId, oldIndexId, newIndexId);