Remove "recheck" argument from check_index_is_clusterable()

The last usage of this argument in this routine can be tracked down to
7e2f9062, aka 11 years ago.  Getting rid of this argument can also be an
advantage for extensions calling check_index_is_clusterable(), as it
removes any need to worry about the meaning of what a recheck would be
at this level.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20220411140609.GF26620@telsasoft.com

src/backend/commands/cluster.c

@@ -232,7 +232,7 @@ cluster(ParseState *pstate, ClusterStmt *stmt, bool isTopLevel)
 	if (rel != NULL)
 	{
 		Assert(rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);
-		check_index_is_clusterable(rel, indexOid, true, AccessShareLock);
+		check_index_is_clusterable(rel, indexOid, AccessShareLock);
 		rtcs = get_tables_to_cluster_partitioned(cluster_context, indexOid);
 
 		/* close relation, releasing lock on parent table */
@@ -434,7 +434,7 @@ cluster_rel(Oid tableOid, Oid indexOid, ClusterParams *params)
 
 	/* Check heap and index are valid to cluster on */
 	if (OidIsValid(indexOid))
-		check_index_is_clusterable(OldHeap, indexOid, recheck, AccessExclusiveLock);
+		check_index_is_clusterable(OldHeap, indexOid, AccessExclusiveLock);
 
 	/*
 	 * Quietly ignore the request if this is a materialized view which has not
@@ -480,7 +480,7 @@ cluster_rel(Oid tableOid, Oid indexOid, ClusterParams *params)
  * protection here.
  */
 void
-check_index_is_clusterable(Relation OldHeap, Oid indexOid, bool recheck, LOCKMODE lockmode)
+check_index_is_clusterable(Relation OldHeap, Oid indexOid, LOCKMODE lockmode)
 {
 	Relation	OldIndex;
 

src/backend/commands/tablecmds.c

@@ -14055,7 +14055,7 @@ ATExecClusterOn(Relation rel, const char *indexName, LOCKMODE lockmode)
 						indexName, RelationGetRelationName(rel))));
 
 	/* Check index is valid to cluster on */
-	check_index_is_clusterable(rel, indexOid, false, lockmode);
+	check_index_is_clusterable(rel, indexOid, lockmode);
 
 	/* And do the work */
 	mark_index_clustered(rel, indexOid, false);

src/include/commands/cluster.h

@@ -34,7 +34,7 @@ typedef struct ClusterParams
 extern void cluster(ParseState *pstate, ClusterStmt *stmt, bool isTopLevel);
 extern void cluster_rel(Oid tableOid, Oid indexOid, ClusterParams *params);
 extern void check_index_is_clusterable(Relation OldHeap, Oid indexOid,
-									   bool recheck, LOCKMODE lockmode);
+									   LOCKMODE lockmode);
 extern void mark_index_clustered(Relation rel, Oid indexOid, bool is_internal);
 
 extern Oid	make_new_heap(Oid OIDOldHeap, Oid NewTableSpace, Oid NewAccessMethod,