2026-03-12 20:23:15

tpt/demos/spm_synonym.sql

@@ -0,0 +1,52 @@
+-- Copyright 2019 Tanel Poder. All rights reserved. More info at https://blog.tanelpoder.com
+-- Licensed under the Apache License, Version 2.0. See LICENSE.txt for terms & conditions.
+
+-- this demos that a SQL Plan Baseline will still apply, even a synonym repoints to a different table.
+-- the table has to have the same name (as otherwise the plan hash value changes), but the schema
+-- is not part of plan hash value.
+
+PROMPT This script will drop some tables called "T". 
+PROMPT Hit enter to continue, CTRL+C to cancel...
+PAUSE 
+
+ALTER SESSION SET optimizer_use_sql_plan_baselines=TRUE;
+
+DROP TABLE system.t;
+DROP TABLE scott.t;
+DROP SYNONYM syn;
+
+CREATE TABLE system.t AS SELECT * FROM dba_objects;
+CREATE TABLE  scott.t AS SELECT * FROM system.t;
+
+CREATE INDEX system.i ON system.t (object_id);
+CREATE INDEX scott.i ON  scott.t (object_id);
+
+EXEC DBMS_STATS.GATHER_TABLE_STATS('SYSTEM','T', cascade=>TRUE);
+EXEC DBMS_STATS.GATHER_TABLE_STATS('SCOTT' ,'T', cascade=>TRUE);
+
+-- First point SYN to system schema
+CREATE SYNONYM syn FOR system.t;
+
+SELECT COUNT(owner) FROM syn t WHERE object_id = 12345;
+
+@x
+
+SELECT /*+ FULL(t) */ COUNT(owner) FROM syn t WHERE object_id = 12345;
+
+@x
+
+@create_sql_baseline bfwpapz4cfwz2 2966233522 3v3yzqv6dp704
+
+SELECT COUNT(owner) FROM syn t WHERE object_id = 12345;
+
+@x
+
+-- Then point SYN to scott schema and run the same query text
+DROP SYNONYM syn;
+CREATE SYNONYM syn FOR scott.t;
+
+SELECT COUNT(owner) FROM syn t WHERE object_id = 12345;
+
+@x
+
+@drop_sql_baseline SQL_547b571057dbd3d4