Remove pg_am.amindexnulls.

The only use we have had for amindexnulls is in determining whether an
index is safe to cluster on; but since the addition of the amclusterable
flag, that usage is pretty redundant.

In passing, clean up assorted sloppiness from the last patch that touched
pg_am.h: Natts_pg_am was wrong, and ambuildempty was not documented.

1 files changed, 0 insertions, 37 deletions

diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
index 560f42b65e8..19c3cf9674c 100644
--- a/src/backend/commands/cluster.c
+++ b/src/backend/commands/cluster.c
@@ -436,43 +436,6 @@ check_index_is_clusterable(Relation OldHeap, Oid indexOid, bool recheck, LOCKMOD
 				 errmsg("cannot cluster on partial index \"%s\"",
 						RelationGetRelationName(OldIndex))));
 
-	if (!OldIndex->rd_am->amindexnulls)
-	{
-		AttrNumber	colno;
-
-		/*
-		 * If the AM doesn't index nulls, then it's a partial index unless we
-		 * can prove all the rows are non-null.  Note we only need look at the
-		 * first column; multicolumn-capable AMs are *required* to index nulls
-		 * in columns after the first.
-		 */
-		colno = OldIndex->rd_index->indkey.values[0];
-		if (colno > 0)
-		{
-			/* ordinary user attribute */
-			if (!OldHeap->rd_att->attrs[colno - 1]->attnotnull)
-				ereport(ERROR,
-						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-						 errmsg("cannot cluster on index \"%s\" because access method does not handle null values",
-								RelationGetRelationName(OldIndex)),
-						 recheck
-						 ? errhint("You might be able to work around this by marking column \"%s\" NOT NULL, or use ALTER TABLE ... SET WITHOUT CLUSTER to remove the cluster specification from the table.",
-						 NameStr(OldHeap->rd_att->attrs[colno - 1]->attname))
-						 : errhint("You might be able to work around this by marking column \"%s\" NOT NULL.",
-					  NameStr(OldHeap->rd_att->attrs[colno - 1]->attname))));
-		}
-		else if (colno < 0)
-		{
-			/* system column --- okay, always non-null */
-		}
-		else
-			/* index expression, lose... */
-			ereport(ERROR,
-					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-					 errmsg("cannot cluster on expressional index \"%s\" because its index access method does not handle null values",
-							RelationGetRelationName(OldIndex))));
-	}
-
 	/*
 	 * Disallow if index is left over from a failed CREATE INDEX CONCURRENTLY;
 	 * it might well not contain entries for every heap row, or might not even