Sometimes a simple question turns out to be harder than expected.
“Can we see if a particular SQL execution in AWR used a baselined plan?”
Initial thoughts might be:
Q: Does DBMS_XPLAN.DISPLAY_AWR tell us this?
A: Apparently not. See below. This question could also be rephrased as two other possible questions:
Q:Isn’t there a column on DBA_HIST_SQLSTAT which tell us this?
A: No. You’d think there should be. There is a SQL_PROFILE column. There isn’t a SQL_PLAN_BASELINE column.
There also isn’t an EXACT_MATCHING_SIGNATURE although there is a FORCE_MATCHING_SIGNATURE.
Q: Is it in DBA_HIST_SQL_PLAN.OTHER_XML?
A. No although this is where DBMS_XPLAN.DISPLAY_AWR gets it’s notes about cardinality feedback and dynamic sampling from.
First of all, Let’s see that it’s not shown in DBMS_XPLAN.DISPLAY_AWR.
Let’s get a sql statement baselined, in AWR and not in memory.
The usual setup
SQL> create table t1
2 (col1 number
3 ,col2 varchar2(50)
4 ,flag varchar2(2));
Table created.
SQL> insert into t1
2 select rownum
3 , lpad('X',50,'X')
4 , case when rownum = 1
5 then 'Y1'
6 when rownum = 2
7 then 'Y2'
8 when mod(rownum,2) = 0
9 then 'N1'
10 else 'N2'
11 end
12 from dual
13* connect by rownum <= 100000
SQL> /
100000 rows created.
SQL> commit;
Commit complete.
Get a plan and put it in a baseline:
SQL> var n varchar2(2);
SQL> exec :n := 'N1';
PL/SQL procedure successfully completed.
SQL> select count(*), max(col2) from t1 where flag = :n;
select * from table(dbms_xplan.display_cursor);
COUNT(*) MAX(COL2)
---------- --------------------------------------------------
49999 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
SQL> select * from table(dbms_xplan.display_cursor);
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
SQL_ID 731b98a8u0knf, child number 0
-------------------------------------
select count(*), max(col2) from t1 where flag = :n
Plan hash value: 3724264953
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 221 (100)| |
| 1 | SORT AGGREGATE | | 1 | 30 | | |
|* 2 | TABLE ACCESS FULL| T1 | 50254 | 1472K| 221 (1)| 00:00:03 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter("FLAG"=:N)
Note
-----
- dynamic sampling used for this statement (level=2)
SQL> declare
2 l_op pls_integer;
3 begin
4 l_op :=
5 dbms_spm.load_plans_from_cursor_cache('731b98a8u0knf');
6* end;
SQL> /
PL/SQL procedure successfully completed.
Verify that DBMS_XPLAN.DISPLAY_CURSOR reports baseline usage:
SQL> select count(*), max(col2) from t1 where flag = :n;
COUNT(*) MAX(COL2)
---------- --------------------------------------------------
49999 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
SQL> select * from table(dbms_xplan.display_cursor);
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
SQL_ID 731b98a8u0knf, child number 0
-------------------------------------
select count(*), max(col2) from t1 where flag = :n
Plan hash value: 3724264953
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 221 (100)| |
| 1 | SORT AGGREGATE | | 1 | 30 | | |
|* 2 | TABLE ACCESS FULL| T1 | 50254 | 1472K| 221 (1)| 00:00:03 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter("FLAG"=:N)
Note
-----
- dynamic sampling used for this statement (level=2)
- SQL plan baseline SQL_PLAN_13w748wknkcwd616acf47 used for this statement
See that dynamic_sampling note most likely comes from OTHER_XML and Baseline note doesn’t, it comes from V$SQL:
SQL>select sql_id
2 , to_char(exact_matching_signature) sig
3 , plan_hash_value
4 , sql_plan_baseline
5 from v$sql
6* where sql_id = '731b98a8u0knf'
SQL> /
SQL_ID SIG PLAN_HASH_VALUE SQL_PLAN_BASELINE
------------- ---------------------------------------- --------------- ------------------------------
731b98a8u0knf 1292784087274697613 3724264953 SQL_PLAN_13w748wknkcwd616acf47
SQL> set long 10000
SQL> select other_xml
2 from v$sql_plan
3 where sql_id = '731b98a8u0knf'
4* and other_xml is not null
SQL> /
OTHER_XML
--------------------------------------------------------------------------------
<other_xml><info type="db_version">11.2.0.3</info><info type="parse_schema"><![C
DATA["E668983_DBA"]]></info><info type="dynamic_sampling">2</info><info type="pl
an_hash">3724264953</info><info type="plan_hash_2">1634389831</info><peeked_bind
s><bind nam=":N" pos="1" dty="1" csi="178" frm="1" mxl="32">4e31</bind></peeked_
binds><outline_data><hint><![CDATA[IGNORE_OPTIM_EMBEDDED_HINTS]]></hint><hint><!
[CDATA[OPTIMIZER_FEATURES_ENABLE('11.2.0.3')]]></hint><hint><![CDATA[DB_VERSION(
'11.2.0.3')]]></hint><hint><![CDATA[OPT_PARAM('query_rewrite_enabled' 'false')]]
></hint><hint><![CDATA[ALL_ROWS]]></hint><hint><![CDATA[OUTLINE_LEAF(@"SEL$1")]]
></hint><hint><![CDATA[FULL(@"SEL$1" "T1"@"SEL$1")]]></hint></outline_data></oth
er_xml>
Now, let’s add statement to AWR, do an AWR snap and flush the SP:
SQL> exec dbms_workload_repository.add_colored_sql('731b98a8u0knf');
PL/SQL procedure successfully completed.
SQL> exec dbms_workload_repository.create_snapshot;
PL/SQL procedure successfully completed.
SQL> alter system flush shared_pool;
System altered.
Now if we look back at the plan in memory, there’s nothing there.
SQL> select * from v$sql where sql_id = '731b98a8u0knf';
no rows selected
SQL> select * from table(dbms_xplan.display_cursor('731b98a8u0knf'));
PLAN_TABLE_OUTPUT
------------------------------------------------------------
SQL_ID: 731b98a8u0knf, child number: 0 cannot be found
But the SQL is in AWR and let’s see that DBMS_XPLAN.DISPLAY_AWR does not tells us that a baseline is used:
SQL> select * from table(dbms_xplan.display_awr('731b98a8u0knf'));
PLAN_TABLE_OUTPUT
---------------------------------------------------------------
SQL_ID 731b98a8u0knf
--------------------
select count(*), max(col2) from t1 where flag = :n
Plan hash value: 3724264953
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 221 (100)| |
| 1 | SORT AGGREGATE | | 1 | 30 | | |
| 2 | TABLE ACCESS FULL| T1 | 50238 | 1471K| 221 (1)| 00:00:03 |
---------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement (level=2)
But it will tell us if a sql profile is used because it can via DBA_HIST_SQLSTAT.SQL_PROFILE – I leave that exercise to the reader.
So, back to the original question:
“Can we see if a particular SQL execution in AWR used a baselined plan?”
I’ve never needed to do this but as an exercise we can infer this connection by the presence of a baselined plan with the same phv2 but it’s convoluted.
It may be that there are simpler ways but it seems to me that we need to:
- Get the exact_matching_signature from the sql text
- Get the phv2 out of DBA_HIST_SQL_PLAN.OTHER_XML
- Match that phv2 with planid which is not exposed in DBA_SQL_PLAN_BASELINES but is in the underlying SYS.SQLOBJ$ tables
SQL> with subq_mysql as
2 (select sql_id
3 , (select dbms_sqltune.sqltext_to_signature(ht.sql_text)
4 from dual) sig
5 from dba_hist_sqltext ht
6 where sql_id = '731b98a8u0knf')
7 , subq_baselines as
8 (select b.signature
9 , b.plan_name
10 , b.accepted
11 , b.created
12 , o.plan_id
13 from subq_mysql ms
14 , dba_sql_plan_baselines b
15 , sys.sqlobj$ o
16 where b.signature = ms.sig
17 and o.signature = b.signature
18 and o.name = b.plan_name)
19 , subq_awr_plans as
20 (select sn.snap_id
21 , to_char(sn.end_interval_time,'DD-MON-YYYY HH24:MI') dt
22 , hs.sql_id
23 , hs.plan_hash_value
24 , t.phv2
25 , ms.sig
26 from subq_mysql ms
27 , dba_hist_sqlstat hs
28 , dba_hist_snapshot sn
29 , dba_hist_sql_plan hp
30 , xmltable('for $i in /other_xml/info
31 where $i/@type eq "plan_hash_2"
32 return $i'
33 passing xmltype(hp.other_xml)
34 columns phv2 number path '/') t
35 where hs.sql_id = ms.sql_id
36 and sn.snap_id = hs.snap_id
37 and sn.instance_number = hs.instance_number
38 and hp.sql_id = hs.sql_id
39 and hp.plan_hash_value = hs.plan_hash_value
40 and hp.other_xml is not null)
41 select awr.*
42 , nvl((select max('Y')
43 from subq_baselines b
44 where b.signature = awr.sig
45 and b.accepted = 'YES'),'N') does_baseline_exist
46 , nvl2(b.plan_id,'Y','N') is_baselined_plan
47 , to_char(b.created,'DD-MON-YYYY HH24:MI') when_baseline_created
48 from subq_awr_plans awr
49 , subq_baselines b
50 where b.signature (+) = awr.sig
51 and b.plan_id (+) = awr.phv2
52* order by awr.snap_id
SQL> /
SNAP_ID DT SQL_ID PLAN_HASH_VALUE PHV2 SIG D I WHEN_BASELINE_CRE
---------- ----------------- ------------- --------------- ---------- ---------- - - -----------------
8703 05-FEB-2014 15:18 731b98a8u0knf 3724264953 1634389831 1.2928E+18 Y Y 05-FEB-2014 15:08
SQL>
Surprising.
Unless, of course, I’ve overlooked something bleeding obvious.
Related posts:
- How does SQL Plan Management match SQL statements to SQL plan baselines?
- Plan_hash_value and internal temporary table names
- Forced Cursor Sharing And Virtual Columns
- Forced Cursor Sharing And Virtual Columns
- SQL Gone Bad – But Plan Not Changed? – Part 1
- What the heck is the INTERNAL_FUNCTION in execution plan predicate section?
- Obsolete cursors
- ORs, IN lists and LNNVL
- Which of my sql statements are using dynamic sampling?
- Reported Execution Plan Anomalies