Archive for the ‘Tuning’ Category.

Cardinality Feedback

I ran into an interesting issue last week having to do with plan stability. The problem description went something like this:

“I have a statement that runs relatively quickly the first time I run it (around 12 seconds). Subsequent executions always run much slower, usually around 20 or 30 minutes. If I flush the shared pool and run it again elapsed time is back to 12 seconds or so.”

The query looked a little like this:

Continue reading ‘Cardinality Feedback’ »

Embarcadero Performance Panel

Karen Morton, Cary MIllsap and I will be participating in a on-line panel discussion about Oracle Performance on July 28th. Since we all worked together in the past we thought it would be a fun to listen to each other answer questions. Embarcadero is sponsoring this event and invited us to participate. Here’s a graphic from the mailer they sent out.

I only point it out because Cary and Karen look like they are posing for a picture, while I, as usual, look like someone just poured a drink down my pants. That’s normal though. I’ve been told I have a great face for radio.

You can sign up here: Register Now!

How to Lock SQL Profiles Generated by SQL Tuning Advisor

I’ve mentioned (many times) that I think SQL Profiles that are generated by the SQL Tuning Advisor (STA) tend to sour over time.

After seeing it happen at a few sites I began to wonder why. So first a few facts about the SQL Profiles that STA generates:

  1. They are simply a set hints that get applied to statements behind the scenes during parsing
  2. They consist mainly of OPT_ESTIMATE hints which modify optimizer calculations
  3. They also may contain direct statistics modification hints (COLUMN_STATS, TABLE_STATS)
  4. They usually contain a OPTIMIZER_FEATURES_ENABLED hint
  5. They very occasionally contain other environment type hints (FIRST_ROWS, etc…)
  6. They do not contain directive hints (FULL, INDEX, NESTED_LOOP, etc..)
  7. The names of STA profiles start with SYS_SQLPROF
  8. STA’s goal is to do a more through job of analyzing a SQL statement to get a better plan

I wrote a little query (sql_profile_distinct_hint.sql) to pull a list of hints from a 10g database along with the number of their occurrences and ran it on several production systems where STA Profiles had been created. Here’s the output from a  system that had 14 STA Profiles.

SQL> @sql_profile_distinct_hints
Enter value for profile_name: SYS_SQLPROF%
 
HINT                                                 COUNT(*)
-------------------------------------------------- ----------
COLUMN_STATS                                               13
FIRST_ROWS                                                  1
IGNORE_OPTIM_EMBEDDED_HINTS                                 1
INDEX_STATS                                                 1
OPTIMIZER_FEATURES_ENABLE                                  14
OPT_ESTIMATE                                              178
TABLE_STATS                                                 2

Notice that the vast majority of hints are of the OPT_ESTIMATE variety. Now let’s have a look at the actual hints contained in a STA Profile.

 
SYS@LAB112> @sql_profile_hints
Enter value for profile_name: SYS_SQLPROF_0126f1743c7d0005
 
HINT
------------------------------------------------------------------------------------------------
IGNORE_OPTIM_EMBEDDED_HINTS
OPTIMIZER_FEATURES_ENABLE(default) 
OPT_ESTIMATE(@"SEL$86A1760A", TABLE, "A"@"SEL$6", SCALE_ROWS=2207.090256)
OPT_ESTIMATE(@"SEL$86A1760A", TABLE, "A"@"SEL$5", SCALE_ROWS=2261.586312)
COLUMN_STATS("KSO"."SKEW", "PK_COL", scale, length=5)
COLUMN_STATS("KSO"."SKEW", "COL1", scale, length=4 distinct=828841 nulls=12.8723033 min=1 max=1000000)
TABLE_STATS("KSO"."SKEW", scale, blocks=162294 rows=35183107.66)
 
7 rows selected.

So on this particular STA Profile, the OPT_ESTIMATE hint has been used to tell the optimizer to change the estimate of rows for table A in query block SEL$6 by multiplying it by 2207 (roughly). In addition, there are hints which are basically hard coding table stats and column stats. So as you can see, these hints, while they may be accurate when the Profile is created, are unlikely to remain accurate over the long haul. In fairness, the OPT_ESTIMATE hint does make sense in situations where the optimizer will never get a calculation correct because of a short coming in it’s abilities (correlated columns is a good example of this type of situation). And in those conditions, implementing a STA generated Profile is a valid long term approach. But in my experience this is the exception rather than the rule.

So what are STA Profiles good for? Well two things:

First, they are very good at showing us where the optimizer is having a problem. If you look at the hints that are generated, it is easy to identify the OPT_ESTIMATE hints where the scaling factors are off the chart (hint: anything with an exponent is a place where the optimizer is struggling). This is easy to do with my sql_profile_hints.sql script by the way. Here’s a set of OPT_ESTIMATE hints. Can you spot the place where the optimizer is really having a problem?

OPT_ESTIMATE(@"SEL$5DA710D3", INDEX_FILTER, "F"@"SEL$1", IDX$$_1AA260002, SCALE_ROWS=8.883203639e-06) 
OPT_ESTIMATE(@"SEL$5DA710D3", INDEX_SKIP_SCAN, "F"@"SEL$1", IDX$$_1AA260002, SCALE_ROWS=8.883203639e-06) 
OPT_ESTIMATE(@"SEL$5DA710D3", JOIN, ("B"@"SEL$1", "A"@"SEL$1"), SCALE_ROWS=4.446153275) 
OPT_ESTIMATE(@"SEL$5DA710D3", JOIN, ("C"@"SEL$1", "A"@"SEL$1"), SCALE_ROWS=7.884506683) 
OPT_ESTIMATE(@"SEL$5DA710D3", JOIN, ("E"@"SEL$1", "A"@"SEL$1"), SCALE_ROWS=25.60960842) 
OPT_ESTIMATE(@"SEL$5DA710D3", JOIN, ("F"@"SEL$1", "B"@"SEL$1"), SCALE_ROWS=26.34181566) 
OPT_ESTIMATE(@"SEL$5DA710D3", JOIN, ("F"@"SEL$1", "B"@"SEL$1", "A"@"SEL$1"), SCALE_ROWS=839.9683673) 
OPT_ESTIMATE(@"SEL$5DA710D3", TABLE, "D"@"SEL$1", SCALE_ROWS=5.083144561)
OPT_ESTIMATE(@"SEL$5", INDEX_SCAN, "C"@"SEL$5", ORDER_FG_ITEM_IX3, SCALE_ROWS=0.2507281101)

It’s the first two lines and whatever alias F refers to is our problem area. The OPT_ESTIMATE hint tells the optimizer to decrease it’s estimate by a factor of 8.883203639e-06. So the optimizer has vastly overestimated the rows that will be returned by the index.

Second, STA Profiles are sometimes capable of producing better plans. This is primarily due to the fact that STA can take as long as you give it to analyze a statement, making sure that all the optimizer’s calculations are correct. It does this by running various pieces of the statement and checking that the number of rows the optimizer has estimated are actually correct. Obviously this can take a while on complex statements, much longer than the optimizer is allowed when parsing a statement. But as I’ve already shown, the SQL Profiles that get created to enable those better plans have a pretty good chance of going sour on us over time.

Which leads me to the point of this post. We can have our cake and eat it too! We can create the SQL Profile as recommended by STA and then “lock” the plan into place by converting the OPT_ESTIMATE hints to directive type hints. I put the word “lock” in quotes because there is really no such thing as “locking” a plan. It’s just that using directive hints as opposed to OPT_ESTIMATE hints, significantly lowers the probability of the plan changing in the future. So how do we make this conversion. Well I have a script for that called lock_STA_profile.sql. Here’s an example showing how it works.

 
SYS@LAB112> @sql_profiles
Enter value for sql_text: 
Enter value for name: 
 
NAME                           CATEGORY        STATUS   SQL_TEXT                                                               FORCE
------------------------------ --------------- -------- ---------------------------------------------------------------------- -----
PROFILE_fgn6qzrvrjgnz          DEFAULT         DISABLED select /*+ index(a SKEW_COL1) */ avg(pk_col) from kso.skew a           NO
PROFILE_8hjn3vxrykmpf          DEFAULT         DISABLED select /*+ invalid_hint (doda) */ avg(pk_col) from kso.skew where col1 NO
PROFILE_69k5bhm12sz98          DEFAULT         DISABLED SELECT dbin.instance_number,        dbin.db_name, dbin.instance_name,  NO
PROFILE_8js5bhfc668rp          DEFAULT         DISABLED select /*+ index(a SKEW_COL2_COL1) */ avg(pk_col) from kso.skew a wher NO
PROFILE_bxd77v75nynd8          DEFAULT         DISABLED select /*+ parallel (a 4) */ avg(pk_col) from kso.skew a where col1 >  NO
PROFILE_7ng34ruy5awxq          DEFAULT         DISABLED select i.obj#,i.ts#,i.file#,i.block#,i.intcols,i.type#,i.flags,i.prope NO
PROF_6kymwy3guu5uq_1388734953  DEFAULT         ENABLED  select 1                                                               YES
PROFILE_cnpx9s9na938m_MANUAL   DEFAULT         ENABLED  select /*+ opt_param('statistics_level','all') */ * from kso.skew wher NO
PROF_79m8gs9wz3ndj_3723858078  DEFAULT         ENABLED  /* SQL Analyze(252,1) */ select avg(pk_col) from kso.skew              NO
PROFILE_9ywuaagwscbj7_GPS      DEFAULT         ENABLED  select avg(pk_col) from kso.skew                                       NO
PROF_arcvrg5na75sw_3723858078  DEFAULT         ENABLED  select /*+ index(skew@sel$1 skew_col1) */ avg(pk_col) from kso.skew wh NO
SYS_SQLPROF_01274114fc2b0006   DEFAULT         ENABLED  select i.table_owner, i.table_name, i.index_name, FUNCIDX_STATUS, colu NO
SYS_SQLPROF_0127d10ffaa60000   DEFAULT         ENABLED  select table_owner||'.'||table_name tname , index_name, index_type, st NO
SYS_SQLPROF_01281e513ace0000   DEFAULT         ENABLED  SELECT TASK_LIST.TASK_ID FROM (SELECT /*+ NO_MERGE(T) ORDERED */ T.TAS NO
coe_abwg9nwg8prsj_3723858078   DEFAULT         ENABLED                                                                         NO
PROF_84q0zxfzn5u6s_2650913906  TEST            ENABLED  select avg(pk_col) from kso.skew                                       NO
PROF_0pvj94afp6faw_FULL        DEFAULT         ENABLED  select /* test 1 hint */ avg(pk_col) from kso.skew a where col1 = 2222 NO
PROF_875qbqc2gw2qz_4201340344  DEFAULT         ENABLED  select /* NOT IN */ department_name                                    NO
PROF_09gdkwq1bs48h_167097056   DEFAULT         ENABLED  select /*+ index (skew skew_col3_col2_col1) */ count(*) from kso.skew  NO
PROFILE_4cp821ufcwvgc_moved    DEFAULT         ENABLED  select count(*) from kso.skew where col3 = '01-jan-10'                 NO
PROF_8wvgj0n4kh6dx_2650913906  DEFAULT         ENABLED  select avg(pk_col) from kso.skew a where col1 = 333333                 NO
PROFILE_g737q1pfmbvjj_moved    DEFAULT         ENABLED  select /*+ full (skew) */ avg(pk_col) from kso.skew where col1 = 13613 NO
PROFILE_cvdnr0b8dcxzz_MANUAL   DEFAULT         ENABLED  select /* aasdas */ avg(pk_col) from kso.skew where col1 = 136133      NO
PROF_719syuvrm29tq_931251584   DEFAULT         ENABLED  SELECT IOBJID, IDOBJID, INAME, IOWNER, IOWNERID, ISPACE, ITSNO, IFILEN NO
PROF_g4gp07gt2z920_105323984   DEFAULT         ENABLED  update sys.scheduler$_job set  last_start_date = :1, running_instance  NO
 
25 rows selected.
 
SYS@LAB112> @sql_profile_hints
Enter value for profile_name: SYS_SQLPROF_01281e513ace0000
 
HINT
------------------------------------------------------------------------------------------------
IGNORE_OPTIM_EMBEDDED_HINTS
OPTIMIZER_FEATURES_ENABLE(default)
FIRST_ROWS(1)
OPT_ESTIMATE(@"SEL$86A1760A", TABLE, "A"@"SEL$6", SCALE_ROWS=2207.090256)
OPT_ESTIMATE(@"SEL$86A1760A", TABLE, "A"@"SEL$5", SCALE_ROWS=2261.586312)
 
5 rows selected.
 
SYS@LAB112> @find_sql
Enter value for sql_text: SELECT TASK_LIST.TASK_ID FROM (SELECT /*+ NO_MERGE(T) ORD%
Enter value for sql_id: 
 
SQL_ID         CHILD  PLAN_HASH EXECS AVG_ETIME  AVG_LIO SQL_TEXT
------------- ------ ---------- ----- --------- -------- --------------------------------------------------
bqfx5q2jas08u      0 2496534803    86       .00       12 SELECT TASK_LIST.TASK_ID FROM (SELECT /*+ NO_MERGE
                                                         (T) ORDERED */ T.TASK_ID FROM (SELECT * FROM DBA_A
                                                         DVISOR_TASKS ORDER BY TASK_ID DESC) T, DBA_ADVISOR
                                                         _PARAMETERS_PROJ P1, DBA_ADVISOR_PARAMETERS_PROJ P
                                                         2 WHERE T.ADVISOR_NAME='ADDM' AND T.STATUS = 'COMP
                                                         LETED' AND T.EXECUTION_START >= (SYSDATE - 1) AND
                                                         T.HOW_CREATED = 'AUTO' AND T.TASK_ID = P1.TASK_ID
                                                         AND P1.PARAMETER_NAME = 'INSTANCE' AND P1.PARAMETE
                                                         R_VALUE = SYS_CONTEXT('USERENV','INSTANCE') AND T.
                                                         TASK_ID = P2.TASK_ID AND P2.PARAMETER_NAME = 'DB_I
                                                         D' AND P2.PARAMETER_VALUE = TO_CHAR(:B1 ) ORDER BY
                                                          T.TASK_ID DESC) TASK_LIST WHERE ROWNUM = 1
 
 
1 row selected.
 
SYS@LAB112> @dplan
Enter value for sql_id: bqfx5q2jas08u
Enter value for child_no: 
 
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------
SQL_ID  bqfx5q2jas08u, child number 0
-------------------------------------
SELECT TASK_LIST.TASK_ID FROM (SELECT /*+ NO_MERGE(T) ORDERED */
T.TASK_ID FROM (SELECT * FROM DBA_ADVISOR_TASKS ORDER BY TASK_ID DESC)
T, DBA_ADVISOR_PARAMETERS_PROJ P1, DBA_ADVISOR_PARAMETERS_PROJ P2 WHERE
T.ADVISOR_NAME='ADDM' AND T.STATUS = 'COMPLETED' AND T.EXECUTION_START
>= (SYSDATE - 1) AND T.HOW_CREATED = 'AUTO' AND T.TASK_ID = P1.TASK_ID
AND P1.PARAMETER_NAME = 'INSTANCE' AND P1.PARAMETER_VALUE =
SYS_CONTEXT('USERENV','INSTANCE') AND T.TASK_ID = P2.TASK_ID AND
P2.PARAMETER_NAME = 'DB_ID' AND P2.PARAMETER_VALUE = TO_CHAR(:B1 )
ORDER BY T.TASK_ID DESC) TASK_LIST WHERE ROWNUM = 1
 
Plan hash value: 2496534803
 
-------------------------------------------------------------------------------------------------------------
| Id  | Operation                          | Name                   | Rows  | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                   |                        |       |       |     9 (100)|          |
|*  1 |  COUNT STOPKEY                     |                        |       |       |            |          |
|   2 |   VIEW                             |                        |     2 |    26 |     9   (0)| 00:00:01 |
|   3 |    NESTED LOOPS                    |                        |       |       |            |          |
|   4 |     NESTED LOOPS                   |                        |     2 |   240 |     9   (0)| 00:00:01 |
|*  5 |      FILTER                        |                        |       |       |            |          |
|   6 |       NESTED LOOPS OUTER           |                        |     2 |   188 |     7   (0)| 00:00:01 |
|   7 |        NESTED LOOPS                |                        |     2 |   126 |     5   (0)| 00:00:01 |
|*  8 |         TABLE ACCESS BY INDEX ROWID| WRI$_ADV_TASKS         |     2 |    74 |     3   (0)| 00:00:01 |
|   9 |          INDEX FULL SCAN DESCENDING| WRI$_ADV_TASKS_PK      |   822 |       |     2   (0)| 00:00:01 |
|* 10 |         TABLE ACCESS BY INDEX ROWID| WRI$_ADV_PARAMETERS    |     1 |    26 |     1   (0)| 00:00:01 |
|* 11 |          INDEX UNIQUE SCAN         | WRI$_ADV_PARAMETERS_PK |     1 |       |     0   (0)|          |
|* 12 |        TABLE ACCESS BY INDEX ROWID | WRI$_ADV_EXECUTIONS    |     1 |    31 |     1   (0)| 00:00:01 |
|* 13 |         INDEX UNIQUE SCAN          | WRI$_ADV_EXECS_PK      |     1 |       |     0   (0)|          |
|* 14 |      INDEX UNIQUE SCAN             | WRI$_ADV_PARAMETERS_PK |     1 |       |     0   (0)|          |
|* 15 |     TABLE ACCESS BY INDEX ROWID    | WRI$_ADV_PARAMETERS    |     1 |    26 |     1   (0)| 00:00:01 |
-------------------------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   1 - filter(ROWNUM=1)
   5 - filter((DECODE(NVL("E"."STATUS","A"."STATUS"),1,'INITIAL',2,'EXECUTING',3,'COMPLETED',4,'INTER
              RUPTED',5,'CANCELLED',6,'FATAL ERROR')='COMPLETED' AND
              NVL("E"."EXEC_START","A"."EXEC_START")>=SYSDATE@!-1))
   8 - filter(("A"."ADVISOR_NAME"='ADDM' AND "A"."HOW_CREATED"='AUTO' AND
              BITAND("A"."PROPERTY",6)=4))
  10 - filter("A"."VALUE"=TO_CHAR(:B1))
  11 - access("A"."ID"="A"."TASK_ID" AND "A"."NAME"='DB_ID')
  12 - filter("A"."ADVISOR_ID"="E"."ADVISOR_ID")
  13 - access("A"."ID"="E"."TASK_ID" AND "A"."LAST_EXEC_NAME"="E"."NAME")
  14 - access("A"."ID"="A"."TASK_ID" AND "A"."NAME"='INSTANCE')
  15 - filter("A"."VALUE"=SYS_CONTEXT('USERENV','INSTANCE'))
 
Note
-----
   - automatic DOP: Computed Degree of Parallelism is 1 because of parallel threshold
   - SQL profile SYS_SQLPROF_01281e513ace0000 used for this statement
 
 
57 rows selected.
 
SYS@LAB112> @lock_STA_profile
Enter value for sql_id: bqfx5q2jas08u
Enter value for child_no (0): 0
Enter value for new_profile_name (PROF_sqlid_planhash): 
Enter value for force_matching (FALSE): 
 
PL/SQL procedure successfully completed.
 
SYS@LAB112> @sql_profiles
Enter value for sql_text: 
Enter value for name: %bqfx5q2jas08u%
 
NAME                           CATEGORY        STATUS   SQL_TEXT                                                               FORCE
------------------------------ --------------- -------- ---------------------------------------------------------------------- -----
PROF_bqfx5q2jas08u_2496534803  DEFAULT         ENABLED  SELECT TASK_LIST.TASK_ID FROM (SELECT /*+ NO_MERGE(T) ORDERED */ T.TAS NO
 
SYS@LAB112> @sql_profile_hints
Enter value for profile_name: PROF_bqfx5q2jas08u_2496534803
 
HINT
------------------------------------------------------------------------------------------------
IGNORE_OPTIM_EMBEDDED_HINTS
OPTIMIZER_FEATURES_ENABLE('11.2.0.1')
DB_VERSION('11.2.0.1')
FIRST_ROWS(1)
NO_PARALLEL
OUTLINE_LEAF(@"SEL$86A1760A")
MERGE(@"SEL$5")
MERGE(@"SEL$532C0C35")
MERGE(@"SEL$6")
OUTLINE_LEAF(@"SEL$1")
OUTLINE(@"SEL$2")
OUTLINE(@"SEL$5")
OUTLINE(@"SEL$532C0C35")
MERGE(@"SEL$4")
OUTLINE(@"SEL$6")
OUTLINE(@"SEL$58B2FD6B")
ELIMINATE_OBY(@"SEL$3")
OUTLINE(@"SEL$4")
OUTLINE(@"SEL$3")
NO_ACCESS(@"SEL$1" "TASK_LIST"@"SEL$1")
INDEX_DESC(@"SEL$86A1760A" "A"@"SEL$4" ("WRI$_ADV_TASKS"."ID"))
INDEX_RS_ASC(@"SEL$86A1760A" "A"@"SEL$6" ("WRI$_ADV_PARAMETERS"."TASK_ID" "WRI$_ADV_PARAMETERS"."NAME"))
INDEX_RS_ASC(@"SEL$86A1760A" "E"@"SEL$4" ("WRI$_ADV_EXECUTIONS"."TASK_ID" "WRI$_ADV_EXECUTIONS"."NAME"))
INDEX(@"SEL$86A1760A" "A"@"SEL$5" ("WRI$_ADV_PARAMETERS"."TASK_ID" "WRI$_ADV_PARAMETERS"."NAME"))
LEADING(@"SEL$86A1760A" "A"@"SEL$4" "A"@"SEL$6" "E"@"SEL$4" "A"@"SEL$5")
USE_NL(@"SEL$86A1760A" "A"@"SEL$6")
USE_NL(@"SEL$86A1760A" "E"@"SEL$4")
USE_NL(@"SEL$86A1760A" "A"@"SEL$5")
NLJ_BATCHING(@"SEL$86A1760A" "A"@"SEL$5")
 
29 rows selected.
 
SYS@LAB112> @sql_profiles
Enter value for sql_text: 
Enter value for name: SYS%
 
NAME                           CATEGORY        STATUS   SQL_TEXT                                                               FORCE
------------------------------ --------------- -------- ---------------------------------------------------------------------- -----
SYS_SQLPROF_01274114fc2b0006   DEFAULT         ENABLED  select i.table_owner, i.table_name, i.index_name, FUNCIDX_STATUS, colu NO
SYS_SQLPROF_0127d10ffaa60000   DEFAULT         ENABLED  select table_owner||'.'||table_name tname , index_name, index_type, st NO
SYS_SQLPROF_01281e513ace0000   SAVED           ENABLED  SELECT TASK_LIST.TASK_ID FROM (SELECT /*+ NO_MERGE(T) ORDERED */ T.TAS NO
 
3 rows selected.
 
SYS@LAB112> @sql_profile_hints
Enter value for profile_name: SYS_SQLPROF_01281e513ace0000
 
HINT
------------------------------------------------------------------------------------------------
IGNORE_OPTIM_EMBEDDED_HINTS
OPTIMIZER_FEATURES_ENABLE(default)
FIRST_ROWS(1)
OPT_ESTIMATE(@"SEL$86A1760A", TABLE, "A"@"SEL$6", SCALE_ROWS=2207.090256)
OPT_ESTIMATE(@"SEL$86A1760A", TABLE, "A"@"SEL$5", SCALE_ROWS=2261.586312)
 
5 rows selected.
 
SYS@LAB112>

So in this example I listed all the SQL Profiles in existence on the system (using sql_profiles.sql). Then I showed the hints associated with STA Profile, SYS_SQLPROF_01281e513ace0000 with sql_profile_hints.sql. Then I located the sql statement in v$sql using the find_sql.sql script. Then I used dbms_xplan (via the dplan.sql script) to show the plan for the statement (proving that it was using the STA Profile). Then I used the lock_STA_profile.sql script to create a directive hint based Profile in place of the OPT_ESTIMATE hint based Profile. Then I showed the hints for the new SQL Profile. Note that the original STA Profile is not dropped, but rather moved to the SAVED category, so you can still look at its hints as I have done at the end of this example.

So that’s it. This is a complex topic and I have blogged about it before on numerous occasions. You may want to look back at this post, Oracle Support Sanctions Manually Created SQL Profiles, to get a better feel for where the hints came from that are used to replace the OPT_ESTIMATE hints. By the way, Jonathan Lewis and Tom Kyte have also written about this feature. (I trust you can find them via Google)

Also, I have written a chapter on Plan Stability in the upcoming Apress book, Pro Oracle SQL. The chapter is 65 or so pages long and it covers SQL Profiles in depth, so if you are hungry for more info on this topic, I highly recommend it. ;)

You can pre-order the book here: Pro Oracle SQL (if you are so inclined)

It should be released in a few weeks.

Hotsos Symposium 2010 Presentations

I got an email a few days ago asking if I would provide the scripts from my Hotsos Symposium 2010 presentations. I didn’t even realize the presentations had been posted anywhere but I managed to find them on my company’s website. So anyway, I decided to go ahead and post a link to the PDF’s and the scripts here as well. So click on the pretty pictures to get the PDFs and the cleverly titled text links to get the accompanying zip files with the scripts.

Controlling Execution Plans Zip File

My Favorite Scripts 2010 Zip File


Oh and Bob Sneed as “Disco Duck” (Thanks Marco)

Oracle Support Sanctions Manually Created SQL Profiles!

I originally titled this post: “SQLT – coe_xfr_sql_profile.sql”

Catchy title huh? – (that’s why I changed it)

I’ve been promoting the use of SQL Profiles as a plan control mechanism for some time. The basic idea is to use the undocumented procedure dbms_sqltune.import_sql_profile to build a set of hints to be applied behind the scenes via a SQL Profile. The hints can be created anyway can think of, but one of my favorite ways to generate them is to pull the hints from the other_xml field of v$sql_plan. This is a technique suggested to me originally by Randolf Geist. I have used this approach several times in the past but occasionally I’ve had a few doubts as to whether this is a good idea or even if SQL Profiles can apply all valid hints (see Jonathan Lewis’s comments on this post, Why Oracle Isn’t Using My Profile, where he expresses some doubts as well – he’s also written a bit about SQL Profiles on his site as you might imagine).

So anyway, I just found out this week that there is a script published on Oracle’s Support site that does exactly the same thing. It’s part of the SQLT zip file published in note 215187.1. By the way, SQLT has quite a bit of interesting information in it and the source (PL/SQL) is not wrapped, so it’s worth having a look at. There’s not much in the way of information about it out there, although I did see a reference to it in a comment on one of Jonathan’s recent posts. Maybe I’ll get around to doing another post on that topic some other time. Anyway, the name of the SQL Profile building script is coe_xfr_sql_profile.sql. It basically pulls the hints from the other_xml field of v$sql_plan and turns them into a SQL Profile. So I’m feeling better about myself now that I know that this approach is at least in some way sanctioned by Oracle support.

Here’s an example:

 
SYS@LAB112> @fs
Enter value for sql_text: %skew%
Enter value for sql_id: 
 
SQL_ID         CHILD  PLAN_HASH      EXECS     AVG_ETIME      AVG_LIO SQL_TEXT
------------- ------ ---------- ---------- ------------- ------------ ------------------------------------------------------------
688rj6tv1bav0      0  568322376          1          6.78      163,077 select avg(pk_col) from kso.skew where col1 = 1
abwg9nwg8prsj      0 3723858078          1           .01           39 select avg(pk_col) from kso.skew where col1 = 136135
 
2 rows selected.
 
SYS@LAB112> @sql_hints
Enter value for sql_id: abwg9nwg8prsj
Enter value for child_no: 0
 
OUTLINE_HINTS
-----------------------------------------------------------------------------------------------------------------------------------------------------------
IGNORE_OPTIM_EMBEDDED_HINTS
OPTIMIZER_FEATURES_ENABLE('11.2.0.1')
DB_VERSION('11.2.0.1')
ALL_ROWS
OUTLINE_LEAF(@"SEL$1")
INDEX_RS_ASC(@"SEL$1" "SKEW"@"SEL$1" ("SKEW"."COL1"))
 
6 rows selected.
 
SYS@LAB112> @coe_xfr_sql_profile    
 
Parameter 1:
SQL_ID (required)
 
Enter value for 1: abwg9nwg8prsj          
 
 
PLAN_HASH_VALUE AVG_ET_SECS
--------------- -----------
     3723858078        .006
 
Parameter 2:
PLAN_HASH_VALUE (required)
 
Enter value for 2: 3723858078
 
Values passed:
~~~~~~~~~~~~~
SQL_ID         : "abwg9nwg8prsj"
PLAN_HASH_VALUE: "3723858078"
 
 
Execute coe_xfr_sql_profile_abwg9nwg8prsj_3723858078.sql
on TARGET system in order to create a custom SQL Profile
with plan 3723858078 linked to adjusted sql_text.
 
 
COE_XFR_SQL_PROFILE completed.
SQL>@coe_xfr_sql_profile_abwg9nwg8prsj_3723858078.sql
SQL>REM
SQL>REM $Header: 215187.1 coe_xfr_sql_profile_abwg9nwg8prsj_3723858078.sql 11.4.1.4 2010/07/23 csierra $
SQL>REM
SQL>REM Copyright (c) 2000-2010, Oracle Corporation. All rights reserved.
SQL>REM
SQL>REM AUTHOR
SQL>REM   carlos.sierra@oracle.com
SQL>REM
SQL>REM SCRIPT
SQL>REM   coe_xfr_sql_profile_abwg9nwg8prsj_3723858078.sql
SQL>REM
SQL>REM DESCRIPTION
SQL>REM   This script is generated by coe_xfr_sql_profile.sql
SQL>REM   It contains the SQL*Plus commands to create a custom
SQL>REM   SQL Profile for SQL_ID abwg9nwg8prsj based on plan hash
SQL>REM   value 3723858078.
SQL>REM   The custom SQL Profile to be created by this script
SQL>REM   will affect plans for SQL commands with signature
SQL>REM   matching the one for SQL Text below.
SQL>REM   Review SQL Text and adjust accordingly.
SQL>REM
SQL>REM PARAMETERS
SQL>REM   None.
SQL>REM
SQL>REM EXAMPLE
SQL>REM   SQL> START coe_xfr_sql_profile_abwg9nwg8prsj_3723858078.sql;
SQL>REM
SQL>REM NOTES
SQL>REM   1. Should be run as SYSTEM or SYSDBA.
SQL>REM   2. User must have CREATE ANY SQL PROFILE privilege.
SQL>REM   3. SOURCE and TARGET systems can be the same or similar.
SQL>REM   4. To drop this custom SQL Profile after it has been created:
SQL>REM  EXEC DBMS_SQLTUNE.DROP_SQL_PROFILE('coe_abwg9nwg8prsj_3723858078');
SQL>REM   5. Be aware that using DBMS_SQLTUNE requires a license
SQL>REM  for the Oracle Tuning Pack.
SQL>REM
SQL>WHENEVER SQLERROR EXIT SQL.SQLCODE;
SQL>REM
SQL>VAR signature NUMBER;
SQL>REM
SQL>DECLARE
  2  sql_txt CLOB;
  3  h       SYS.SQLPROF_ATTR;
  4  BEGIN
  5  sql_txt := q'[
  6  select avg(pk_col) from kso.skew where col1 = 136135
  7  ]';
  8  h := SYS.SQLPROF_ATTR(
  9  q'[BEGIN_OUTLINE_DATA]',
 10  q'[IGNORE_OPTIM_EMBEDDED_HINTS]',
 11  q'[OPTIMIZER_FEATURES_ENABLE('11.2.0.1')]',
 12  q'[DB_VERSION('11.2.0.1')]',
 13  q'[ALL_ROWS]',
 14  q'[OUTLINE_LEAF(@"SEL$1")]',
 15  q'[INDEX_RS_ASC(@"SEL$1" "SKEW"@"SEL$1" ("SKEW"."COL1"))]',
 16  q'[END_OUTLINE_DATA]');
 17  :signature := DBMS_SQLTUNE.SQLTEXT_TO_SIGNATURE(sql_txt);
 18  DBMS_SQLTUNE.IMPORT_SQL_PROFILE (
 19  sql_text    => sql_txt,
 20  profile     => h,
 21  name        => 'coe_abwg9nwg8prsj_3723858078',
 22  description => 'coe abwg9nwg8prsj 3723858078 '||:signature||'',
 23  category    => 'DEFAULT',
 24  validate    => TRUE,
 25  replace     => TRUE,
 26  force_match => FALSE /* TRUE:FORCE (match even when different literals in SQL). FALSE:EXACT (similar to CURSOR_SHARING) */ );
 27  END;
 28  /
 
PL/SQL procedure successfully completed.
 
SQL>WHENEVER SQLERROR CONTINUE
SQL>SET ECHO OFF;
 
            SIGNATURE
---------------------
 15022055147995020558
 
 
... manual custom SQL Profile has been created
 
 
COE_XFR_SQL_PROFILE_abwg9nwg8prsj_3723858078 completed
 
SYS@LAB112> @sql_profiles
Enter value for sql_text: 
Enter value for name: 
 
NAME                           CATEGORY        STATUS   SQL_TEXT                                                               FORCE
------------------------------ --------------- -------- ---------------------------------------------------------------------- -----
PROFILE_fgn6qzrvrjgnz          DEFAULT         DISABLED select /*+ index(a SKEW_COL1) */ avg(pk_col) from kso.skew a           NO
PROFILE_8hjn3vxrykmpf          DEFAULT         DISABLED select /*+ invalid_hint (doda) */ avg(pk_col) from kso.skew where col1 NO
PROFILE_69k5bhm12sz98          DEFAULT         DISABLED SELECT dbin.instance_number,        dbin.db_name, dbin.instance_name,  NO
PROFILE_8js5bhfc668rp          DEFAULT         DISABLED select /*+ index(a SKEW_COL2_COL1) */ avg(pk_col) from kso.skew a wher NO
PROFILE_bxd77v75nynd8          DEFAULT         DISABLED select /*+ parallel (a 4) */ avg(pk_col) from kso.skew a where col1 >  NO
PROFILE_7ng34ruy5awxq          DEFAULT         DISABLED select i.obj#,i.ts#,i.file#,i.block#,i.intcols,i.type#,i.flags,i.prope NO
SYS_SQLPROF_0126f1743c7d0005   SAVED           ENABLED  select avg(pk_col) from kso.skew                                       NO
PROF_6kymwy3guu5uq_1388734953  DEFAULT         ENABLED  select 1                                                               YES
PROFILE_cnpx9s9na938m_MANUAL   DEFAULT         ENABLED  select /*+ opt_param('statistics_level','all') */ * from kso.skew wher NO
PROF_79m8gs9wz3ndj_3723858078  DEFAULT         ENABLED  /* SQL Analyze(252,1) */ select avg(pk_col) from kso.skew              NO
PROFILE_9ywuaagwscbj7_GPS      DEFAULT         ENABLED  select avg(pk_col) from kso.skew                                       NO
PROF_arcvrg5na75sw_3723858078  DEFAULT         ENABLED  select /*+ index(skew@sel$1 skew_col1) */ avg(pk_col) from kso.skew wh NO
SYS_SQLPROF_01274114fc2b0006   DEFAULT         ENABLED  select i.table_owner, i.table_name, i.index_name, FUNCIDX_STATUS, colu NO
SYS_SQLPROF_0127d10ffaa60000   DEFAULT         ENABLED  select table_owner||'.'||table_name tname , index_name, index_type, st NO
SYS_SQLPROF_01281e513ace0000   DEFAULT         ENABLED  SELECT TASK_LIST.TASK_ID FROM (SELECT /*+ NO_MERGE(T) ORDERED */ T.TAS NO
PROFILE_5bgcrdwfhbc83_EXACT    DEFAULT         ENABLED  select avg(pk_col) from kso.skew where col1 = :"SYS_B_0"               YES
coe_abwg9nwg8prsj_3723858078   DEFAULT         ENABLED                                                                         NO
 
17 rows selected.
 
SYS@LAB112> -- that's interesting - looks like the sql_text has gotten wiped out
SYS@LAB112> -- let's see if it works anyway
SYS@LAB112> 
SYS@LAB112> select avg(pk_col) from kso.skew where col1 = 136135;
 
AVG(PK_COL)
-----------
   15636135
 
SYS@LAB112> @fs
Enter value for sql_text: select avg(pk_col) from kso.skew where col1 = 136135
Enter value for sql_id: 
 
SQL_ID         CHILD  PLAN_HASH      EXECS     AVG_ETIME      AVG_LIO SQL_TEXT
------------- ------ ---------- ---------- ------------- ------------ ------------------------------------------------------------
abwg9nwg8prsj      0 3723858078          1           .02           47 select avg(pk_col) from kso.skew where col1 = 136135
 
1 row selected.
 
SYS@LAB112> @dplan
Enter value for sql_id: abwg9nwg8prsj
Enter value for child_no: 
 
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------
SQL_ID  abwg9nwg8prsj, child number 0
-------------------------------------
select avg(pk_col) from kso.skew where col1 = 136135
 
Plan hash value: 3723858078
 
------------------------------------------------------------------------------------------
| Id  | Operation                    | Name      | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |           |       |       |    32 (100)|          |
|   1 |  SORT AGGREGATE              |           |     1 |    24 |            |          |
|   2 |   TABLE ACCESS BY INDEX ROWID| SKEW      |    32 |   768 |    32   (0)| 00:00:01 |
|*  3 |    INDEX RANGE SCAN          | SKEW_COL1 |    32 |       |     3   (0)| 00:00:01 |
------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   3 - access("COL1"=136135)
 
Note
-----
   - SQL profile coe_abwg9nwg8prsj_3723858078 used for this statement
 
 
24 rows selected.

So it is very similar to my create_sql_profile.sql script. The Oracle COE script does have the advantage of creating an output script that can be run to create the SQL Profile. That means you have a chance to edit the hints before creating the SQL Profile. It also means you can easily move a SQL Profile from one environment (TEST for example) to another (PROD for example).

But the best thing about it is that I no longer have to be concerned about using an undocumented procedure to do something that it may not have been intended to do in the first place!