In my previous post, I have shown that loading Adaptive Plans in the SQL Plan Baseline leads to using the original plan. Well, actually, this is true when you capture them via the OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES parameter.
Thanks to a tweet by Neil Chandler, I’ve realized that it was a good idea to show also the case when the plan is loaded manually.
When the adaptive plan switches to the alternative plan, the plan_hash_value also changes, and can be loaded manually in the baseline with DBMS_SPM.
Let’s reset everything and retry quickly to:
- Capture the plan automatically (this will lead to the original plan)
- Load the plan manually (I will specify to load the alternative plan, if resolved)
- Drop the plan captured automatically
- Use the newly accepted baseline
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SQL> connect / as sysdba Connected. SQL> DECLARE 2 v_dropped_plans number; 3 BEGIN 4 v_dropped_plans := DBMS_SPM.DROP_SQL_PLAN_BASELINE ( 5 sql_handle => 'SQL_6c4c6680810dd01a' 6 ); 7 DBMS_OUTPUT.PUT_LINE('dropped ' || v_dropped_plans || ' plans'); 8 END; 9 / PL/SQL procedure successfully completed. SQL> select sql_handle, plan_name, sql_text, enabled, accepted, fixed from dba_sql_plan_baselines; no rows selected SQL> alter system flush shared_pool; System altered. SQL> select sql_id, plan_hash_value, child_number from v$sql where sql_id='1km5kczcgr0fr'; no rows selected SQL> connect ludo/ludo Connected. SQL> ALTER SESSION SET OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES = TRUE; Session altered. SELECT /*+ GATHER_PLAN_STATISTICS */ 2 a.data AS tab1_data, 3 b.data AS tab2_data 4 FROM tab1 a 5 JOIN tab2 b ON b.tab1_id = a.id 6 WHERE a.code = 'ONE'; TAB1_DATA TAB2_DATA ---------- ---------- ... 30 rows selected. SQL> r 1 SELECT /*+ GATHER_PLAN_STATISTICS */ 2 a.data AS tab1_data, 3 b.data AS tab2_data 4 FROM tab1 a 5 JOIN tab2 b ON b.tab1_id = a.id 6* WHERE a.code = 'ONE' TAB1_DATA TAB2_DATA ---------- ---------- ... 30 rows selected. SQL> ALTER SESSION SET OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES = FALSE; Session altered. SQL> select sql_id, plan_hash_value, child_number from v$sql where sql_id='1km5kczcgr0fr'; SQL_ID PLAN_HASH_VALUE CHILD_NUMBER --------------------------------------- --------------- ------------ 1km5kczcgr0fr 2672205743 1 SELECT /*+ GATHER_PLAN_STATISTICS */ a.data AS tab1_data, 2 3 b.data AS tab2_data 4 FROM tab1 a 5 JOIN tab2 b ON b.tab1_id = a.id 6 WHERE a.code = 'ONE'; TAB1_DATA TAB2_DATA ---------- ---------- ... 30 rows selected. SQL> select sql_id, plan_hash_value, child_number from v$sql where sql_id='1km5kczcgr0fr'; SQL_ID PLAN_HASH_VALUE CHILD_NUMBER --------------------------------------- --------------- ------------ 1km5kczcgr0fr 2672205743 1 1km5kczcgr0fr 2672205743 2 SQL> ALTER SESSION SET OPTIMIZER_USE_SQL_PLAN_BASELINES = FALSE; Session altered. SELECT /*+ GATHER_PLAN_STATISTICS */ 2 a.data AS tab1_data, 3 b.data AS tab2_data 4 FROM tab1 a 5 JOIN tab2 b ON b.tab1_id = a.id 6 WHERE a.code = 'ONE'; TAB1_DATA TAB2_DATA ---------- ---------- ... 30 rows selected. SQL> select sql_id, plan_hash_value, child_number from v$sql where sql_id='1km5kczcgr0fr'; SQL_ID PLAN_HASH_VALUE CHILD_NUMBER --------------------------------------- --------------- ------------ 1km5kczcgr0fr 1599395313 0 1km5kczcgr0fr 2672205743 1 1km5kczcgr0fr 2672205743 2 SQL> connect / as sysdba Connected. SQL> VARIABLE cnt NUMBER SQL> EXECUTE :cnt := DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE( sql_id => '1km5kczcgr0fr',plan_hash_value => '1599395313'); PL/SQL procedure successfully completed. SQL> select sql_handle, plan_name, sql_text, enabled, accepted, fixed from dba_sql_plan_baselines; SQL_HANDLE PLAN_NAME SQL_TEXT ENABLED ACCEPTED FIXED ------------------------- ----------------------------------- -------------------------------------- --------- --------- --------- SQL_6c4c6680810dd01a SQL_PLAN_6sm36h20hvn0u55a25f73 SELECT /*+ GATHER_PLAN_STATISTICS */ YES YES NO a.data AS tab1_data, b.data A SQL_6c4c6680810dd01a SQL_PLAN_6sm36h20hvn0ud64ac9be SELECT /*+ GATHER_PLAN_STATISTICS */ YES YES NO a.data AS tab1_data, b.data A SQL> select * from table (DBMS_XPLAN.DISPLAY_SQL_PLAN_BASELINE('SQL_6c4c6680810dd01a', format=>'+adaptive')); PLAN_TABLE_OUTPUT ---------------------------------------------------------------------------------- -------------------------------------------------------------------------------- SQL handle: SQL_6c4c6680810dd01a SQL text: SELECT /*+ GATHER_PLAN_STATISTICS */ a.data AS tab1_data, b.data AS tab2_data FROM tab1 a JOIN tab2 b ON b.tab1_id = a.id WHERE a.code = 'ONE' -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Plan name: SQL_PLAN_6sm36h20hvn0u55a25f73 Plan id: 1436704627 Enabled: YES Fixed: NO Accepted: YES Origin: AUTO-CAPTURE Plan rows: From dictionary -------------------------------------------------------------------------------- Plan hash value: 2672205743 --------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 25 | 425 | 3 (0)| 00:00:01 | | 1 | NESTED LOOPS | | 25 | 425 | 3 (0)| 00:00:01 | | 2 | NESTED LOOPS | | 25 | 425 | 3 (0)| 00:00:01 | | 3 | TABLE ACCESS BY INDEX ROWID BATCHED| TAB1 | 1 | 11 | 2 (0)| 00:00:01 | | * 4 | INDEX RANGE SCAN | TAB1_CODE | 1 | | 1 (0)| 00:00:01 | | * 5 | INDEX RANGE SCAN | TAB2_TAB1_FKI | 25 | | 0 (0)| 00:00:01 | | 6 | TABLE ACCESS BY INDEX ROWID | TAB2 | 25 | 150 | 1 (0)| 00:00:01 | --------------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 4 - access("A"."CODE"='ONE') 5 - access("B"."TAB1_ID"="A"."ID") Note ----- - this is an adaptive plan (rows marked '-' are inactive) -------------------------------------------------------------------------------- Plan name: SQL_PLAN_6sm36h20hvn0ud64ac9be Plan id: 3595225534 Enabled: YES Fixed: NO Accepted: YES Origin: MANUAL-LOAD Plan rows: From dictionary -------------------------------------------------------------------------------- Plan hash value: 1599395313 ---------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ---------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | 3 (100)| | | * 1 | HASH JOIN | | 25 | 425 | 3 (0)| 00:00:01 | | 2 | TABLE ACCESS BY INDEX ROWID BATCHED| TAB1 | 1 | 11 | 2 (0)| 00:00:01 | | * 3 | INDEX RANGE SCAN | TAB1_CODE | 1 | | 1 (0)| 00:00:01 | | 4 | TABLE ACCESS FULL | TAB2 | 25 | 150 | 1 (0)| 00:00:01 | ---------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 1 - access("B"."TAB1_ID"="A"."ID") 3 - access("A"."CODE"='ONE') Note ----- - this is an adaptive plan (rows marked '-' are inactive) 65 rows selected. SQL> VARIABLE cnt NUMBER SQL> EXECUTE :cnt := DBMS_SPM.DROP_SQL_PLAN_BASELINE( SQL_HANDLE => 'SQL_6c4c6680810dd01a',plan_name => 'SQL_PLAN_6sm36h20hvn0u55a25f73'); PL/SQL procedure successfully completed. SQL> select sql_handle, plan_name, sql_text, enabled, accepted, fixed from dba_sql_plan_baselines; SQL_HANDLE PLAN_NAME SQL_TEXT ENABLED ACCEPTED FIXED ------------------------- ----------------------------------- -------------------------------------- --------- --------- --------- SQL_6c4c6680810dd01a SQL_PLAN_6sm36h20hvn0ud64ac9be SELECT /*+ GATHER_PLAN_STATISTICS */ YES YES NO a.data AS tab1_data, b.data A SQL> conn ludo/ludo Connected. SELECT /*+ GATHER_PLAN_STATISTICS */ 2 a.data AS tab1_data, 3 b.data AS tab2_data 4 FROM tab1 a 5 JOIN tab2 b ON b.tab1_id = a.id 6 WHERE a.code = 'ONE'; TAB1_DATA TAB2_DATA ---------- ---------- ... 30 rows selected. SQL> SELECT * FROM TABLE(DBMS_XPLAN.display_cursor(format => 'allstats last adaptive')); PLAN_TABLE_OUTPUT ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ SQL_ID 1km5kczcgr0fr, child number 2 ------------------------------------- SELECT /*+ GATHER_PLAN_STATISTICS */ a.data AS tab1_data, b.data AS tab2_data FROM tab1 a JOIN tab2 b ON b.tab1_id = a.id WHERE a.code = 'ONE' Plan hash value: 1599395313 --------------------------------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | OMem | 1Mem | Used-Mem | --------------------------------------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 24 |00:00:00.01 | 71 | | | | |* 1 | HASH JOIN | | 1 | 25 | 24 |00:00:00.01 | 71 | 1888K| 1888K| 1921K (0)| | 2 | TABLE ACCESS BY INDEX ROWID BATCHED| TAB1 | 1 | 1 | 10001 |00:00:00.01 | 62 | | | | |* 3 | INDEX RANGE SCAN | TAB1_CODE | 1 | 1 | 10001 |00:00:00.01 | 37 | | | | | 4 | TABLE ACCESS FULL | TAB2 | 1 | 100 | 100 |00:00:00.01 | 9 | | | | --------------------------------------------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 1 - access("B"."TAB1_ID"="A"."ID") 3 - access("A"."CODE"='ONE') Note ----- - SQL plan baseline SQL_PLAN_6sm36h20hvn0ud64ac9be used for this statement 28 rows selected. |
To recap:
- The capture process will always load the original plan
- It is possible to decide to load manually the original one or the alternative one (if resolved)
- Using automatic capture is a bad idea
HTH
—
Ludo
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Hi,
Is it possible to use adaptive sql plan when sql plan management is enabled?
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