Fix subtly-incorrect matching of parent and child partitioned indexes.

When creating a partitioned index, DefineIndex tries to identify
any existing indexes on the partitions that match the partitioned
index, so that it can absorb those as child indexes instead of
building new ones.  Part of the matching is to compare IndexInfo
structs --- but that wasn't done quite right.  We're comparing
the IndexInfo built within DefineIndex itself to one made from
existing catalog contents by BuildIndexInfo.  Notably, while
BuildIndexInfo will run index expressions and predicates through
expression preprocessing, that has not happened to DefineIndex's
struct.  The result is failure to match and subsequent creation
of duplicate indexes.

The easiest and most bulletproof fix is to build a new IndexInfo
using BuildIndexInfo, thereby guaranteeing that the processing done
is identical.

While here, let's also extract the opfamily and collation data
from the new partitioned index, removing ad-hoc logic that
duplicated knowledge about how those are constructed.

Per report from Christophe Pettus.  Back-patch to v11 where
we invented partitioned indexes.

Richard Guo and Tom Lane

Discussion: https://postgr.es/m/8864BFAA-81FD-4BF9-8E06-7DEB8D4164ED@thebuild.com

1 files changed, 17 insertions, 6 deletions

diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 15a57ea9c3d..667f2a4cd16 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -1213,18 +1213,27 @@ DefineIndex(Oid relationId,
 			int			nparts = partdesc->nparts;
 			Oid		   *part_oids = palloc(sizeof(Oid) * nparts);
 			bool		invalidate_parent = false;
+			Relation	parentIndex;
 			TupleDesc	parentDesc;
-			Oid		   *opfamOids;
 
 			pgstat_progress_update_param(PROGRESS_CREATEIDX_PARTITIONS_TOTAL,
 										 nparts);
 
+			/* Make a local copy of partdesc->oids[], just for safety */
 			memcpy(part_oids, partdesc->oids, sizeof(Oid) * nparts);
 
+			/*
+			 * We'll need an IndexInfo describing the parent index.  The one
+			 * built above is almost good enough, but not quite, because (for
+			 * example) its predicate expression if any hasn't been through
+			 * expression preprocessing.  The most reliable way to get an
+			 * IndexInfo that will match those for child indexes is to build
+			 * it the same way, using BuildIndexInfo().
+			 */
+			parentIndex = index_open(indexRelationId, lockmode);
+			indexInfo = BuildIndexInfo(parentIndex);
+
 			parentDesc = RelationGetDescr(rel);
-			opfamOids = palloc(sizeof(Oid) * numberOfKeyAttributes);
-			for (i = 0; i < numberOfKeyAttributes; i++)
-				opfamOids[i] = get_opclass_family(classObjectId[i]);
 
 			/*
 			 * For each partition, scan all existing indexes; if one matches
@@ -1295,9 +1304,9 @@ DefineIndex(Oid relationId,
 					cldIdxInfo = BuildIndexInfo(cldidx);
 					if (CompareIndexInfo(cldIdxInfo, indexInfo,
 										 cldidx->rd_indcollation,
-										 collationObjectId,
+										 parentIndex->rd_indcollation,
 										 cldidx->rd_opfamily,
-										 opfamOids,
+										 parentIndex->rd_opfamily,
 										 attmap))
 					{
 						Oid			cldConstrOid = InvalidOid;
@@ -1424,6 +1433,8 @@ DefineIndex(Oid relationId,
 				free_attrmap(attmap);
 			}
 
+			index_close(parentIndex, lockmode);
+
 			/*
 			 * The pg_index row we inserted for this index was marked
 			 * indisvalid=true.  But if we attached an existing index that is