Move autogenerated array types out of the way during ALTER ... RENAME.

Commit 9aa3c782 added code to allow CREATE TABLE/CREATE TYPE to not fail
when the desired type name conflicts with an autogenerated array type, by
dint of renaming the array type out of the way.  But I (tgl) overlooked
that the same case arises in ALTER TABLE/TYPE RENAME.  Fix that too.
Back-patch to all supported branches.

Report and patch by Vik Fearing, modified a bit by me

Discussion: https://postgr.es/m/0f4ade49-4f0b-a9a3-c120-7589f01d1eb8@2ndquadrant.com

src/backend/catalog/pg_type.c

@@ -695,6 +695,7 @@ RenameTypeInternal(Oid typeOid, const char *newTypeName, Oid typeNamespace)
 	HeapTuple	tuple;
 	Form_pg_type typ;
 	Oid			arrayOid;
+	Oid			oldTypeOid;
 
 	pg_type_desc = heap_open(TypeRelationId, RowExclusiveLock);
 
@@ -708,13 +709,28 @@ RenameTypeInternal(Oid typeOid, const char *newTypeName, Oid typeNamespace)
 
 	arrayOid = typ->typarray;
 
-	/* Just to give a more friendly error than unique-index violation */
-	if (SearchSysCacheExists2(TYPENAMENSP,
-							  CStringGetDatum(newTypeName),
-							  ObjectIdGetDatum(typeNamespace)))
-		ereport(ERROR,
-				(errcode(ERRCODE_DUPLICATE_OBJECT),
-				 errmsg("type \"%s\" already exists", newTypeName)));
+	/* Check for a conflicting type name. */
+	oldTypeOid = GetSysCacheOid2(TYPENAMENSP,
+								 CStringGetDatum(newTypeName),
+								 ObjectIdGetDatum(typeNamespace));
+
+	/*
+	 * If there is one, see if it's an autogenerated array type, and if so
+	 * rename it out of the way.  (But we must skip that for a shell type
+	 * because moveArrayTypeName will do the wrong thing in that case.)
+	 * Otherwise, we can at least give a more friendly error than unique-index
+	 * violation.
+	 */
+	if (OidIsValid(oldTypeOid))
+	{
+		if (get_typisdefined(oldTypeOid) &&
+			moveArrayTypeName(oldTypeOid, newTypeName, typeNamespace))
+			 /* successfully dodged the problem */ ;
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_DUPLICATE_OBJECT),
+					 errmsg("type \"%s\" already exists", newTypeName)));
+	}
 
 	/* OK, do the rename --- tuple is a copy, so OK to scribble on it */
 	namestrcpy(&(typ->typname), newTypeName);
@@ -726,8 +742,12 @@ RenameTypeInternal(Oid typeOid, const char *newTypeName, Oid typeNamespace)
 	heap_freetuple(tuple);
 	heap_close(pg_type_desc, RowExclusiveLock);
 
-	/* If the type has an array type, recurse to handle that */
-	if (OidIsValid(arrayOid))
+	/*
+	 * If the type has an array type, recurse to handle that.  But we don't
+	 * need to do anything more if we already renamed that array type above
+	 * (which would happen when, eg, renaming "foo" to "_foo").
+	 */
+	if (OidIsValid(arrayOid) && arrayOid != oldTypeOid)
 	{
 		char	   *arrname = makeArrayTypeName(newTypeName, typeNamespace);
 

src/test/regress/expected/alter_table.out

@@ -128,6 +128,55 @@ SELECT * FROM tmp_new2;
 
 DROP TABLE tmp_new;
 DROP TABLE tmp_new2;
+--
+-- check renaming to a table's array type's autogenerated name
+-- (the array type's name should get out of the way)
+--
+CREATE TABLE tmp_array (id int);
+CREATE TABLE tmp_array2 (id int);
+SELECT typname FROM pg_type WHERE oid = 'tmp_array[]'::regtype;
+  typname   
+------------
+ _tmp_array
+(1 row)
+
+SELECT typname FROM pg_type WHERE oid = 'tmp_array2[]'::regtype;
+   typname   
+-------------
+ _tmp_array2
+(1 row)
+
+ALTER TABLE tmp_array2 RENAME TO _tmp_array;
+SELECT typname FROM pg_type WHERE oid = 'tmp_array[]'::regtype;
+   typname   
+-------------
+ __tmp_array
+(1 row)
+
+SELECT typname FROM pg_type WHERE oid = '_tmp_array[]'::regtype;
+   typname    
+--------------
+ ___tmp_array
+(1 row)
+
+DROP TABLE _tmp_array;
+DROP TABLE tmp_array;
+-- renaming to table's own array type's name is an interesting corner case
+CREATE TABLE tmp_array (id int);
+SELECT typname FROM pg_type WHERE oid = 'tmp_array[]'::regtype;
+  typname   
+------------
+ _tmp_array
+(1 row)
+
+ALTER TABLE tmp_array RENAME TO _tmp_array;
+SELECT typname FROM pg_type WHERE oid = '_tmp_array[]'::regtype;
+   typname   
+-------------
+ __tmp_array
+(1 row)
+
+DROP TABLE _tmp_array;
 -- ALTER TABLE ... RENAME on non-table relations
 -- renaming indexes (FIXME: this should probably test the index's functionality)
 ALTER INDEX IF EXISTS __onek_unique1 RENAME TO tmp_onek_unique1;

src/test/regress/sql/alter_table.sql

@@ -165,6 +165,26 @@ SELECT * FROM tmp_new2;
 DROP TABLE tmp_new;
 DROP TABLE tmp_new2;
 
+--
+-- check renaming to a table's array type's autogenerated name
+-- (the array type's name should get out of the way)
+--
+CREATE TABLE tmp_array (id int);
+CREATE TABLE tmp_array2 (id int);
+SELECT typname FROM pg_type WHERE oid = 'tmp_array[]'::regtype;
+SELECT typname FROM pg_type WHERE oid = 'tmp_array2[]'::regtype;
+ALTER TABLE tmp_array2 RENAME TO _tmp_array;
+SELECT typname FROM pg_type WHERE oid = 'tmp_array[]'::regtype;
+SELECT typname FROM pg_type WHERE oid = '_tmp_array[]'::regtype;
+DROP TABLE _tmp_array;
+DROP TABLE tmp_array;
+
+-- renaming to table's own array type's name is an interesting corner case
+CREATE TABLE tmp_array (id int);
+SELECT typname FROM pg_type WHERE oid = 'tmp_array[]'::regtype;
+ALTER TABLE tmp_array RENAME TO _tmp_array;
+SELECT typname FROM pg_type WHERE oid = '_tmp_array[]'::regtype;
+DROP TABLE _tmp_array;
 
 -- ALTER TABLE ... RENAME on non-table relations
 -- renaming indexes (FIXME: this should probably test the index's functionality)