From 400c6c6c610dd6af96b4bc5bf39a967cd1e6597b Mon Sep 17 00:00:00 2001
From: Alexey Kondratov <kondratov.aleksey@gmail.com>
Date: Wed, 20 Jan 2021 20:21:12 +0300
Subject: [PATCH v3 1/2] Extract common part from ATExecSetTableSpaceNoStorage
 for a future usage

---
 src/backend/commands/tablecmds.c | 96 +++++++++++++++++++-------------
 src/include/commands/tablecmds.h |  2 +
 2 files changed, 58 insertions(+), 40 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 8687e9a97c..edf14d1e65 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -13291,6 +13291,58 @@ ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode)
 	list_free(reltoastidxids);
 }
 
+/*
+ * SetRelTablespace - modify relation tablespace in the pg_class entry.
+ *
+ * 'reloid' is an Oid of relation to be modified.
+ * 'tablespaceOid' is an Oid of new tablespace.
+ *
+ * Catalog modification is done only if tablespaceOid is different from
+ * the currently set.  Returned bool value is indicating whether any changes
+ * were made or not.
+ */
+bool
+SetRelTablespace(Oid reloid, Oid tablespaceOid)
+{
+	Relation		pg_class;
+	HeapTuple		tuple;
+	Form_pg_class	rd_rel;
+	bool			changed = false;
+	Oid			oldTablespaceOid;
+
+	/* Get a modifiable copy of the relation's pg_class row. */
+	pg_class = table_open(RelationRelationId, RowExclusiveLock);
+
+	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(reloid));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for relation %u", reloid);
+	rd_rel = (Form_pg_class) GETSTRUCT(tuple);
+
+	/* No work if no change in tablespace. */
+	oldTablespaceOid = rd_rel->reltablespace;
+	if (tablespaceOid != oldTablespaceOid ||
+		(tablespaceOid == MyDatabaseTableSpace && OidIsValid(oldTablespaceOid)))
+	{
+		/* Update the pg_class row. */
+		rd_rel->reltablespace = (tablespaceOid == MyDatabaseTableSpace) ?
+			InvalidOid : tablespaceOid;
+		CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);
+
+		/* Record dependency on tablespace */
+		changeDependencyOnTablespace(RelationRelationId,
+									 reloid, rd_rel->reltablespace);
+
+		changed = true;
+	}
+
+	InvokeObjectPostAlterHook(RelationRelationId, reloid, 0);
+
+	heap_freetuple(tuple);
+	table_close(pg_class, RowExclusiveLock);
+
+	return changed;
+}
+
 /*
  * Special handling of ALTER TABLE SET TABLESPACE for relations with no
  * storage that have an interest in preserving tablespace.
@@ -13301,11 +13353,7 @@ ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode)
 static void
 ATExecSetTableSpaceNoStorage(Relation rel, Oid newTableSpace)
 {
-	HeapTuple	tuple;
-	Oid			oldTableSpace;
-	Relation	pg_class;
-	Form_pg_class rd_rel;
-	Oid			reloid = RelationGetRelid(rel);
+	Oid	reloid = RelationGetRelid(rel);
 
 	/*
 	 * Shouldn't be called on relations having storage; these are processed in
@@ -13319,41 +13367,9 @@ ATExecSetTableSpaceNoStorage(Relation rel, Oid newTableSpace)
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("only shared relations can be placed in pg_global tablespace")));
 
-	/*
-	 * No work if no change in tablespace.
-	 */
-	oldTableSpace = rel->rd_rel->reltablespace;
-	if (newTableSpace == oldTableSpace ||
-		(newTableSpace == MyDatabaseTableSpace && oldTableSpace == 0))
-	{
-		InvokeObjectPostAlterHook(RelationRelationId, reloid, 0);
-		return;
-	}
-
-	/* Get a modifiable copy of the relation's pg_class row */
-	pg_class = table_open(RelationRelationId, RowExclusiveLock);
-
-	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(reloid));
-	if (!HeapTupleIsValid(tuple))
-		elog(ERROR, "cache lookup failed for relation %u", reloid);
-	rd_rel = (Form_pg_class) GETSTRUCT(tuple);
-
-	/* update the pg_class row */
-	rd_rel->reltablespace = (newTableSpace == MyDatabaseTableSpace) ? InvalidOid : newTableSpace;
-	CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);
-
-	/* Record dependency on tablespace */
-	changeDependencyOnTablespace(RelationRelationId,
-								 reloid, rd_rel->reltablespace);
-
-	InvokeObjectPostAlterHook(RelationRelationId, reloid, 0);
-
-	heap_freetuple(tuple);
-
-	table_close(pg_class, RowExclusiveLock);
-
-	/* Make sure the reltablespace change is visible */
-	CommandCounterIncrement();
+	if (SetRelTablespace(reloid, newTableSpace))
+		/* Make sure the reltablespace change is visible */
+		CommandCounterIncrement();
 }
 
 /*
diff --git a/src/include/commands/tablecmds.h b/src/include/commands/tablecmds.h
index 08c463d3c4..35553fd41a 100644
--- a/src/include/commands/tablecmds.h
+++ b/src/include/commands/tablecmds.h
@@ -61,6 +61,8 @@ extern void ExecuteTruncateGuts(List *explicit_rels, List *relids, List *relids_
 
 extern void SetRelationHasSubclass(Oid relationId, bool relhassubclass);
 
+extern bool SetRelTablespace(Oid reloid, Oid tablespaceOid);
+
 extern ObjectAddress renameatt(RenameStmt *stmt);
 
 extern ObjectAddress RenameConstraint(RenameStmt *stmt);

base-commit: 920f853dc948b98a5dc96580c4ee011a302e33e4
-- 
2.20.1