2026-03-12 20:23:15

tpt/ast/02_advanced_rewrite.sql

@@ -0,0 +1,48 @@
+-- Copyright 2018 Tanel Poder. All rights reserved. More info at http://tanelpoder.com
+-- Licensed under the Apache License, Version 2.0. See LICENSE.txt for terms & conditions.
+
+-- GRANT EXECUTE ON sys.dbms_advanced_rewrite TO &user 
+-- there's no public synonym for this package so you should reference it by schema name
+
+exec sys.DBMS_ADVANCED_REWRITE.DROP_REWRITE_EQUIVALENCE ('test_rewrite');
+
+begin
+   sys.DBMS_ADVANCED_REWRITE.DECLARE_REWRITE_EQUIVALENCE (
+      'test_rewrite'
+    , 'select username,created from test_users u where username in (select owner from test_objects o where o.owner = u.username)'
+    , 'select /*+ qb_name(main) no_unnest(@subq) */ username,created from test_users u where username in (select /*+ qb_name(subq) */ owner from test_objects o where o.owner = u.username) and /* careful! */ 1=1'
+    , validate => true
+    , rewrite_mode => 'general'
+   );
+end;
+/
+
+
+alter session set query_rewrite_enabled = true -- this is true by default;
+alter session set query_rewrite_integrity = trusted;
+
+-- if you see a FILTER operation (not a HASH JOIN SEMI) then the rewrite worked
+select username,created from test_users u where username in (select owner from test_objects o where o.owner = u.username);
+@x9a
+
+
+-- an example of how to add a missing ORDER BY to a statement which assumes that GROUP BY always orders data too
+-- (this is not true in 10.2+ where GROUP BY and DISTINCT operations can be done using hashing instead of sorting)
+
+exec sys.DBMS_ADVANCED_REWRITE.DROP_REWRITE_EQUIVALENCE ('test_rewrite_order');
+
+begin
+   sys.DBMS_ADVANCED_REWRITE.DECLARE_REWRITE_EQUIVALENCE (
+      'test_rewrite_order'
+    , 'select owner,count(*) from test_objects group by owner'
+    , 'select * from (select owner,count(*) from test_objects group by owner order by owner)'
+    , validate => true
+    , rewrite_mode => 'text_match'
+   );
+end;
+/
+
+select owner,count(*) from test_objects group by owner;
+@x9a
+
+