AWR: Was a baselined plan used?

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:

1. Get the exact_matching_signature from the sql text
2. Get the phv2 out of DBA_HIST_SQL_PLAN.OTHER_XML
3. 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.