v1-try_index_open.patch

diff --git a/src/backend/access/index/indexam.c b/src/backend/access/index/indexam.c
index b25b03f7ab..f598eb7f74 100644
--- a/src/backend/access/index/indexam.c
+++ b/src/backend/access/index/indexam.c
@@ -114,6 +114,8 @@ static IndexScanDesc index_beginscan_internal(Relation indexRelation,
  * ----------------------------------------------------------------
  */
 
+static inline void validate_index_relation_kind(Relation r);
+
 /* ----------------
  *		index_open - open an index relation by relation OID
  *
@@ -135,12 +137,30 @@ index_open(Oid relationId, LOCKMODE lockmode)
 
 	r = relation_open(relationId, lockmode);
 
-	if (r->rd_rel->relkind != RELKIND_INDEX &&
-		r->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)
-		ereport(ERROR,
-				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-				 errmsg("\"%s\" is not an index",
-						RelationGetRelationName(r))));
+	validate_index_relation_kind(r);
+
+	return r;
+}
+
+/* ----------------
+ *		try_index_open - open a index relation by relation OID
+ *
+ *		Same as index_open, except return NULL instead of failing
+ *		if the relation does not exist.
+ * ----------------
+ */
+Relation
+try_index_open(Oid relationId, LOCKMODE lockmode)
+{
+	Relation	r;
+
+	r = try_relation_open(relationId, lockmode);
+
+	/* leave if index does not exist */
+	if (!r)
+		return NULL;
+
+	validate_index_relation_kind(r);
 
 	return r;
 }
@@ -168,6 +188,24 @@ index_close(Relation relation, LOCKMODE lockmode)
 		UnlockRelationId(&relid, lockmode);
 }
 
+/* ----------------
+ *		validate_index_relation_kind - check the index relation's kind
+ *
+ *		Make sure relkind is index or partitioned index
+ * ----------------
+ */
+static inline void
+validate_index_relation_kind(Relation r)
+{
+	if (r->rd_rel->relkind != RELKIND_INDEX &&
+		r->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is not an index",
+						RelationGetRelationName(r))));
+}
+
+
 /* ----------------
  *		index_insert - insert an index tuple into a relation
  * ----------------
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 143fae01eb..07fc6d57f3 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -3624,7 +3624,24 @@ reindex_index(Oid indexId, bool skip_constraint_checks, char persistence,
 	 * Open the target index relation and get an exclusive lock on it, to
 	 * ensure that no one else is touching this particular index.
 	 */
-	iRel = index_open(indexId, AccessExclusiveLock);
+	if ((params->options & REINDEXOPT_MISSING_OK) != 0)
+		iRel = try_index_open(indexId, AccessExclusiveLock);
+	else
+		iRel = index_open(indexId, AccessExclusiveLock);
+
+	/* if index relation is gone, leave */
+	if (!iRel)
+	{
+		/* Roll back any GUC changes before exit */
+		AtEOXact_GUC(false, save_nestlevel);
+
+		/* Restore userid and security context */
+		SetUserIdAndSecContext(save_userid, save_sec_context);
+
+		/* Close rels, but keep locks */
+		table_close(heapRelation, NoLock);
+		return;
+	}
 
 	if (progress)
 		pgstat_progress_update_param(PROGRESS_CREATEIDX_ACCESS_METHOD_OID,
diff --git a/src/include/access/genam.h b/src/include/access/genam.h
index f31dec6ee0..958fe85235 100644
--- a/src/include/access/genam.h
+++ b/src/include/access/genam.h
@@ -139,6 +139,7 @@ typedef struct IndexOrderByDistance
 #define IndexScanIsValid(scan) PointerIsValid(scan)
 
 extern Relation index_open(Oid relationId, LOCKMODE lockmode);
+extern Relation try_index_open(Oid relationId, LOCKMODE lockmode);
 extern void index_close(Relation relation, LOCKMODE lockmode);
 
 extern bool index_insert(Relation indexRelation,