2026-03-12 20:23:15

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parent eab4b36eca
commit 93039b8489
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--- a/tpt/aot/demo2.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:   demo2.sql
+--
+-- Purpose:     Advanced Oracle Troubleshooting Seminar demo script
+--              Makes a single fetch to generate lots of LIOs by
+--              nested looping over full table scans.
+--              Requires lotslios.sql script from TPT scripts.
+--
+-- Author:      Tanel Poder ( http://www.tanelpoder.com )
+-- Copyright:   (c) Tanel Poder
+--
+--------------------------------------------------------------------------------
+
+prompt Starting Demo2...
+
+-- @@lotslios 1000000000000
+
+--------------------------------------------------------------------------------
+--
+-- File name:   demos/bind_peeking_nested_loops.sql
+-- Purpose:     this script demos how a "wrong" bind variable value
+--              can cause an execution plan to be compiled which is 
+--              very inefficient for the next execution with different bind variable
+--              values (with large number of matching rows) 
+--              the second execution of the query takes very long time to complete
+--              despite adaptive bind variable peeking, which would kick in during the 
+--              next (3rd) execution
+--
+--              This problem happens even on Oracle 11.2 despite adaptive bind peeking
+--              and cardinality feedback (due design, not a bug)
+--              
+-- Author:      Tanel Poder (tanel@e2sn.com)
+-- Copyright:   (c) http://tech.e2sn.com
+--
+--------------------------------------------------------------------------------
+
+DROP TABLE t1;
+DROP TABLE t2;
+DROP TABLE t3;
+
+CREATE TABLE t1 AS SELECT * FROM dba_objects;
+CREATE TABLE t2 AS SELECT * FROM dba_objects;
+CREATE TABLE t3 AS SELECT * FROM dba_objects;
+
+CREATE INDEX i1 ON t1(owner);
+CREATE INDEX i2 ON t2(owner);
+CREATE INDEX i3 ON t3(owner);
+
+EXEC DBMS_STATS.GATHER_TABLE_STATS(user,'T1',cascade=>TRUE, method_opt=>'FOR ALL INDEXED COLUMNS SIZE 254');
+EXEC DBMS_STATS.GATHER_TABLE_STATS(user,'T2',cascade=>TRUE, method_opt=>'FOR ALL INDEXED COLUMNS SIZE 254');
+EXEC DBMS_STATS.GATHER_TABLE_STATS(user,'T3',cascade=>TRUE, method_opt=>'FOR ALL INDEXED COLUMNS SIZE 254');
+
+ALTER SESSION SET OPTIMIZER_INDEX_COST_ADJ=1;
+
+VAR v VARCHAR2(100)
+
+EXEC :v:='SCOTT'
+
+SET TIMING ON
+
+--PROMPT Running query first time, this should be fast (and should use nested loops execution plan)
+
+SELECT
+    MIN(t1.created), MAX(t1.created)
+FROM
+    t1
+  , t2
+  , t3
+WHERE
+    t1.object_id = t2.object_id
+AND t2.object_id = t3.object_id
+AND t1.owner = :v
+AND t2.owner = :v
+AND t3.owner = :v
+/
+
+SET TIMING OFF
+
+--SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(null,null,'ALLSTATS LAST ADVANCED'));
+SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(null,null));
+
+EXEC :v:='SYS'
+
+SET TIMING ON
+
+PROMPT Running the "report"...
+--PROMPT Now running the same query with different bind variables (this query should take very long time)
+
+SELECT
+    MIN(t1.created), MAX(t1.created)
+FROM
+    t1
+  , t2
+  , t3
+WHERE
+    t1.object_id = t2.object_id
+AND t2.object_id = t3.object_id
+AND t1.owner = :v
+AND t2.owner = :v
+AND t3.owner = :v
+/
+