2026-03-12 20:23:15

tpt/demos/cse.sql

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+-- 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.
+
+--------------------------------------------------------------------------------
+--
+-- File name:   demos/cse.sql
+--
+-- Purpose:     Advanced Oracle Troubleshooting Seminar demo script
+--
+--              Demonstrating common subexpression elimination transformation
+--
+-- Author:      Tanel Poder ( http://www.tanelpoder.com )
+--
+-- Copyright:   (c) 2007-2009 Tanel Poder
+--
+--------------------------------------------------------------------------------
+
+set serverout on size 1000000
+
+create or replace function imhere( par in varchar2 )
+    return varchar2
+as
+begin
+    dbms_output.put_line('i''m here!: '||par);
+    return par;
+end;
+/
+
+
+@pd eliminate_common_subexpr
+
+set echo on
+
+select /*+ ORDERED_PREDICATES tanel1 */ * 
+from dual 
+where 
+   (imhere(dummy) = 'X' and length(dummy) = 10) 
+or (imhere(dummy) = 'X' and length(dummy) = 11)
+/
+
+alter session set "_eliminate_common_subexpr"=false;
+
+select /*+ ORDERED_PREDICATES tanel2 */ * 
+from dual 
+where 
+   (imhere(dummy) = 'X' and length(dummy) = 10) 
+or (imhere(dummy) = 'X' and length(dummy) = 11)
+/
+
+set echo off
+
+select /*+ tanel3 */ * 
+from dual 
+where 
+   (imhere(dummy) = 'X' and length(dummy) = 10) 
+or (imhere(dummy) = 'X' and length(dummy) = 11)
+/