Replace pg_class.relhasexclusion with pg_index.indisexclusion.

There isn't any need to track this state on a table-wide basis, and trying
to do so introduces undesirable semantic fuzziness.  Move the flag to
pg_index, where it clearly describes just a single index and can be
immutable after index creation.

src/backend/catalog/heap.c

@@ -703,7 +703,6 @@ InsertPgClassTuple(Relation pg_class_desc,
 	values[Anum_pg_class_relchecks - 1] = Int16GetDatum(rd_rel->relchecks);
 	values[Anum_pg_class_relhasoids - 1] = BoolGetDatum(rd_rel->relhasoids);
 	values[Anum_pg_class_relhaspkey - 1] = BoolGetDatum(rd_rel->relhaspkey);
-	values[Anum_pg_class_relhasexclusion - 1] = BoolGetDatum(rd_rel->relhasexclusion);
 	values[Anum_pg_class_relhasrules - 1] = BoolGetDatum(rd_rel->relhasrules);
 	values[Anum_pg_class_relhastriggers - 1] = BoolGetDatum(rd_rel->relhastriggers);
 	values[Anum_pg_class_relhassubclass - 1] = BoolGetDatum(rd_rel->relhassubclass);

src/backend/catalog/index.c

@@ -96,10 +96,11 @@ static void UpdateIndexRelation(Oid indexoid, Oid heapoid,
 					Oid *classOids,
 					int16 *coloptions,
 					bool primary,
+					bool isexclusion,
 					bool immediate,
 					bool isvalid);
 static void index_update_stats(Relation rel,
-				   bool hasindex, bool isprimary, bool hasexclusion,
+				   bool hasindex, bool isprimary,
 				   Oid reltoastidxid, double reltuples);
 static void IndexCheckExclusion(Relation heapRelation,
 					Relation indexRelation,
@@ -523,6 +524,7 @@ UpdateIndexRelation(Oid indexoid,
 					Oid *classOids,
 					int16 *coloptions,
 					bool primary,
+					bool isexclusion,
 					bool immediate,
 					bool isvalid)
 {
@@ -591,6 +593,7 @@ UpdateIndexRelation(Oid indexoid,
 	values[Anum_pg_index_indnatts - 1] = Int16GetDatum(indexInfo->ii_NumIndexAttrs);
 	values[Anum_pg_index_indisunique - 1] = BoolGetDatum(indexInfo->ii_Unique);
 	values[Anum_pg_index_indisprimary - 1] = BoolGetDatum(primary);
+	values[Anum_pg_index_indisexclusion - 1] = BoolGetDatum(isexclusion);
 	values[Anum_pg_index_indimmediate - 1] = BoolGetDatum(immediate);
 	values[Anum_pg_index_indisclustered - 1] = BoolGetDatum(false);
 	values[Anum_pg_index_indisvalid - 1] = BoolGetDatum(isvalid);
@@ -819,7 +822,6 @@ index_create(Relation heapRelation,
 	indexRelation->rd_rel->relam = accessMethodObjectId;
 	indexRelation->rd_rel->relkind = RELKIND_INDEX;
 	indexRelation->rd_rel->relhasoids = false;
-	indexRelation->rd_rel->relhasexclusion = is_exclusion;
 
 	/*
 	 * store index's pg_class entry
@@ -854,7 +856,7 @@ index_create(Relation heapRelation,
 	 * ----------------
 	 */
 	UpdateIndexRelation(indexRelationId, heapRelationId, indexInfo,
-						classObjectId, coloptions, isprimary,
+						classObjectId, coloptions, isprimary, is_exclusion,
 						!deferrable,
 						!concurrent);
 
@@ -1024,7 +1026,6 @@ index_create(Relation heapRelation,
 		index_update_stats(heapRelation,
 						   true,
 						   isprimary,
-						   is_exclusion,
 						   InvalidOid,
 						   heapRelation->rd_rel->reltuples);
 		/* Make the above update visible */
@@ -1190,7 +1191,6 @@ index_constraint_create(Relation heapRelation,
 		index_update_stats(heapRelation,
 						   true,
 						   true,
-						   false,
 						   InvalidOid,
 						   heapRelation->rd_rel->reltuples);
 
@@ -1375,7 +1375,7 @@ BuildIndexInfo(Relation index)
 	ii->ii_PredicateState = NIL;
 
 	/* fetch exclusion constraint info if any */
-	if (index->rd_rel->relhasexclusion)
+	if (indexStruct->indisexclusion)
 	{
 		RelationGetExclusionInfo(index,
 								 &ii->ii_ExclusionOps,
@@ -1486,7 +1486,6 @@ FormIndexDatum(IndexInfo *indexInfo,
  *
  * hasindex: set relhasindex to this value
  * isprimary: if true, set relhaspkey true; else no change
- * hasexclusion: if true, set relhasexclusion true; else no change
  * reltoastidxid: if not InvalidOid, set reltoastidxid to this value;
  *		else no change
  * reltuples: set reltuples to this value
@@ -1503,7 +1502,7 @@ FormIndexDatum(IndexInfo *indexInfo,
  */
 static void
 index_update_stats(Relation rel,
-				   bool hasindex, bool isprimary, bool hasexclusion,
+				   bool hasindex, bool isprimary,
 				   Oid reltoastidxid, double reltuples)
 {
 	BlockNumber relpages = RelationGetNumberOfBlocks(rel);
@@ -1542,9 +1541,9 @@ index_update_stats(Relation rel,
 	 * It is safe to use a non-transactional update even though our
 	 * transaction could still fail before committing.	Setting relhasindex
 	 * true is safe even if there are no indexes (VACUUM will eventually fix
-	 * it), likewise for relhaspkey and relhasexclusion.  And of course the
-	 * relpages and reltuples counts are correct (or at least more so than the
-	 * old values) regardless.
+	 * it), likewise for relhaspkey.  And of course the relpages and reltuples
+	 * counts are correct (or at least more so than the old values)
+	 * regardless.
 	 */
 
 	pg_class = heap_open(RelationRelationId, RowExclusiveLock);
@@ -1597,14 +1596,6 @@ index_update_stats(Relation rel,
 			dirty = true;
 		}
 	}
-	if (hasexclusion)
-	{
-		if (!rd_rel->relhasexclusion)
-		{
-			rd_rel->relhasexclusion = true;
-			dirty = true;
-		}
-	}
 	if (OidIsValid(reltoastidxid))
 	{
 		Assert(rd_rel->relkind == RELKIND_TOASTVALUE);
@@ -1760,13 +1751,11 @@ index_build(Relation heapRelation,
 	index_update_stats(heapRelation,
 					   true,
 					   isprimary,
-					   (indexInfo->ii_ExclusionOps != NULL),
 					   (heapRelation->rd_rel->relkind == RELKIND_TOASTVALUE) ?
 					   RelationGetRelid(indexRelation) : InvalidOid,
 					   stats->heap_tuples);
 
 	index_update_stats(indexRelation,
-					   false,
 					   false,
 					   false,
 					   InvalidOid,

src/backend/commands/vacuum.c

@@ -524,21 +524,12 @@ vac_update_relstats(Relation relation,
 
 	/*
 	 * If we have discovered that there are no indexes, then there's no
-	 * primary key either, nor any exclusion constraints.  This could be done
-	 * more thoroughly...
+	 * primary key either.  This could be done more thoroughly...
 	 */
-	if (!hasindex)
+	if (pgcform->relhaspkey && !hasindex)
 	{
-		if (pgcform->relhaspkey)
-		{
-			pgcform->relhaspkey = false;
-			dirty = true;
-		}
-		if (pgcform->relhasexclusion && pgcform->relkind != RELKIND_INDEX)
-		{
-			pgcform->relhasexclusion = false;
-			dirty = true;
-		}
+		pgcform->relhaspkey = false;
+		dirty = true;
 	}
 
 	/* We also clear relhasrules and relhastriggers if needed */

src/backend/parser/parse_utilcmd.c

@@ -949,7 +949,7 @@ generateClonedIndexStmt(CreateStmtContext *cxt, Relation source_idx,
 	 * certainly isn't.  If it is or might be from a constraint, we have to
 	 * fetch the pg_constraint record.
 	 */
-	if (index->primary || index->unique || idxrelrec->relhasexclusion)
+	if (index->primary || index->unique || idxrec->indisexclusion)
 	{
 		Oid			constraintId = get_index_constraint(source_relid);
 
@@ -970,7 +970,7 @@ generateClonedIndexStmt(CreateStmtContext *cxt, Relation source_idx,
 			index->initdeferred = conrec->condeferred;
 
 			/* If it's an exclusion constraint, we need the operator names */
-			if (idxrelrec->relhasexclusion)
+			if (idxrec->indisexclusion)
 			{
 				Datum	   *elems;
 				int			nElems;