HOW TO: Post a SQL statement tuning request - template posting

Question

This post is not a question, but similar to Rob van Wijk's "When your query takes too long ..." post should help to improve the quality of the requests for SQL statement tuning here on OTN.
On the OTN forum very often tuning requests about single SQL statements are posted, but the information provided is rather limited, and therefore it's not that simple to provide a meaningful advice. Instead of writing the same requests for additional information over and over again I thought I put together a post that describes how a "useful" post for such a request should look like and what information it should cover.
I've also prepared very detailed step-by-step instructions how to obtain that information on my blog, which can be used to easily gather the required information. It also covers again the details how to post the information properly here, in particular how to use the \ tag to preserve formatting and get a fixed font output:
http://oracle-randolf.blogspot.com/2009/02/basic-sql-statement-performance.html
So again: This post here describes how a "useful" post should look like and what information it ideally covers. The blog post explains in detail how to obtain that information.
In the future, rather than requesting the same additional information and explaining how to obtain it, I'll simply refer to this HOW TO post and the corresponding blog post which describes in detail how to get that information.
*Very important:*
Use the \ tag to enclose any output that should have its formatting preserved as shown below.
So if you want to use fixed font formatting that preserves the spaces etc., do the following:
\   This preserves formatting
\And it will look like this:
   This preserves formatting
   . . .Your post should cover the following information:
1. The SQL and a short description of its purpose
2. The version of your database with 4-digits (e.g. 10.2.0.4)
3. Optimizer related parameters
4. The TIMING and AUTOTRACE output
5. The EXPLAIN PLAN output
6. The TKPROF output snippet that corresponds to your statement
7. If you're on 10g or later, the DBMS_XPLAN.DISPLAY_CURSOR output
The above mentioned blog post describes in detail how to obtain that information.
Your post should have a meaningful subject, e.g. "SQL statement tuning request", and the message body should look similar to the following:
*-- Start of template body --*
The following SQL statement has been identified to perform poorly. It currently takes up to 10 seconds to execute, but it's supposed to take a second at most.
This is the statement:
select
from
         t_demo
where
         type = 'VIEW'
order by
         id;It should return data from a table in a specific order.
The version of the database is 11.1.0.7.
These are the parameters relevant to the optimizer:
SQL>
SQL> show parameter optimizer
NAME                                 TYPE        VALUE
optimizer_capture_sql_plan_baselines boolean     FALSE
optimizer_dynamic_sampling           integer     2
optimizer_features_enable            string      11.1.0.7
optimizer_index_caching              integer     0
optimizer_index_cost_adj             integer     100
optimizer_mode                       string      ALL_ROWS
optimizer_secure_view_merging        boolean     TRUE
optimizer_use_invisible_indexes      boolean     FALSE
optimizer_use_pending_statistics     boolean     FALSE
optimizer_use_sql_plan_baselines     boolean     TRUE
SQL>
SQL> show parameter db_file_multi
NAME                                 TYPE        VALUE
db_file_multiblock_read_count        integer     8
SQL>
SQL> show parameter db_block_size
NAME                                 TYPE        VALUE
db_block_size                        integer     8192
SQL>
SQL> show parameter cursor_sharing
NAME                                 TYPE        VALUE
cursor_sharing                       string      EXACT
SQL>
SQL> column sname format a20
SQL> column pname format a20
SQL> column pval2 format a20
SQL>
SQL> select
  2             sname
  3           , pname
  4           , pval1
  5           , pval2
  6  from
  7           sys.aux_stats$;
SNAME                PNAME                     PVAL1 PVAL2
SYSSTATS_INFO        STATUS                          COMPLETED
SYSSTATS_INFO        DSTART                          01-30-2009 16:25
SYSSTATS_INFO        DSTOP                           01-30-2009 16:25
SYSSTATS_INFO        FLAGS                         0
SYSSTATS_MAIN        CPUSPEEDNW              494,397
SYSSTATS_MAIN        IOSEEKTIM                    10
SYSSTATS_MAIN        IOTFRSPEED                 4096
SYSSTATS_MAIN        SREADTIM
SYSSTATS_MAIN        MREADTIM
SYSSTATS_MAIN        CPUSPEED
SYSSTATS_MAIN        MBRC
SYSSTATS_MAIN        MAXTHR
SYSSTATS_MAIN        SLAVETHR
13 rows selected.Here is the output of EXPLAIN PLAN:
SQL> explain plan for
  2  -- put your statement here
  3  select
  4             *
  5  from
  6             t_demo
  7  where
  8             type = 'VIEW'
  9  order by
10             id;
Explained.
Elapsed: 00:00:00.01
SQL>
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 1390505571
| Id  | Operation                   | Name     | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT            |          |     1 |    60 |     0   (0)| 00:00:01 |
|   1 |  TABLE ACCESS BY INDEX ROWID| T_DEMO   |     1 |    60 |     0   (0)| 00:00:01 |
|*  2 |   INDEX RANGE SCAN          | IDX_DEMO |     1 |       |     0   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - access("TYPE"='VIEW')
14 rows selected.Here is the output of SQL*Plus AUTOTRACE including the TIMING information:
SQL> rem Set the ARRAYSIZE according to your application
SQL> set autotrace traceonly arraysize 100
SQL> select
  2             *
  3  from
  4             t_demo
  5  where
  6             type = 'VIEW'
  7  order by
  8             id;
149938 rows selected.
Elapsed: 00:00:02.21
Execution Plan
Plan hash value: 1390505571
| Id  | Operation                   | Name     | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT            |          |     1 |    60 |     0   (0)| 00:00:01 |
|   1 |  TABLE ACCESS BY INDEX ROWID| T_DEMO   |     1 |    60 |     0   (0)| 00:00:01 |
|*  2 |   INDEX RANGE SCAN          | IDX_DEMO |     1 |       |     0   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - access("TYPE"='VIEW')
Statistics
          0  recursive calls
          0  db block gets
     149101  consistent gets
        800  physical reads
        196  redo size
    1077830  bytes sent via SQL*Net to client
      16905  bytes received via SQL*Net from client
       1501  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
     149938  rows processed
SQL>
SQL> disconnect
Disconnected from Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing optionsThe TKPROF output for this statement looks like the following:
TKPROF: Release 11.1.0.7.0 - Production on Mo Feb 23 10:23:08 2009
Copyright (c) 1982, 2007, Oracle.  All rights reserved.
Trace file: orcl11_ora_3376_mytrace1.trc
Sort options: default
count    = number of times OCI procedure was executed
cpu      = cpu time in seconds executing
elapsed  = elapsed time in seconds executing
disk     = number of physical reads of buffers from disk
query    = number of buffers gotten for consistent read
current  = number of buffers gotten in current mode (usually for update)
rows     = number of rows processed by the fetch or execute call
select
from
         t_demo
where
         type = 'VIEW'
order by
         id
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch     1501      0.53       1.36        800     149101          0      149938
total     1503      0.53       1.36        800     149101          0      149938
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 88 
Rows     Row Source Operation
149938  TABLE ACCESS BY INDEX ROWID T_DEMO (cr=149101 pr=800 pw=0 time=60042 us cost=0 size=60 card=1)
149938   INDEX RANGE SCAN IDX_DEMO (cr=1881 pr=1 pw=0 time=0 us cost=0 size=0 card=1)(object id 74895)
Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  SQL*Net message to client                    1501        0.00          0.00
  db file sequential read                       800        0.05          0.80
  SQL*Net message from client                  1501        0.00          0.69
********************************************************************************The DBMS_XPLAN.DISPLAY_CURSOR output:
SQL> -- put your statement here
SQL> -- use the GATHER_PLAN_STATISTICS hint
SQL> -- if you're not using STATISTICS_LEVEL = ALL
SQL> select /*+ gather_plan_statistics */
  2  *
  3  from
  4  t_demo
  5  where
  6  type = 'VIEW'
  7  order by
  8  id;
149938 rows selected.
Elapsed: 00:00:02.21
SQL>
SQL> select * from table(dbms_xplan.display_cursor(null, null, 'ALLSTATS LAST'));
PLAN_TABLE_OUTPUT
SQL_ID  d4k5acu783vu8, child number 0
select   /*+ gather_plan_statistics */          * from          t_demo
where          type = 'VIEW' order by          id
Plan hash value: 1390505571
| Id  | Operation                   | Name     | Starts | E-Rows | A-Rows |   A-Time   | Buffers | Reads  |
|   0 | SELECT STATEMENT            |          |      1 |        |    149K|00:00:00.02 |     149K|   1183 |
|   1 |  TABLE ACCESS BY INDEX ROWID| T_DEMO   |      1 |      1 |    149K|00:00:00.02 |     149K|   1183 |
|*  2 |   INDEX RANGE SCAN          | IDX_DEMO |      1 |      1 |    149K|00:00:00.02 |    1880 |    383 |
Predicate Information (identified by operation id):
   2 - access("TYPE"='VIEW')
20 rows selected.I'm looking forward for suggestions how to improve the performance of this statement.
*-- End of template body --*
I'm sure that if you follow these instructions and obtain the information described, post them using a proper formatting (don't forget about the \ tag) you'll receive meaningful advice very soon.
So, just to make sure you didn't miss this point:Use proper formatting!
If you think I missed something important in this sample post let me know so that I can improve it.
Regards,
Randolf
Oracle related stuff blog:
http://oracle-randolf.blogspot.com/
SQLTools++ for Oracle (Open source Oracle GUI for Windows):
http://www.sqltools-plusplus.org:7676/
http://sourceforge.net/projects/sqlt-pp/                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

Answer 1

Alex Nuijten wrote:
...you missed the proper formatting of the Autotrace section ;-)Alex,
can't reproduce, does it still look unformatted? Or are you simply kidding? :-)
Randolf
PS: Just noticed that it actually sometimes doesn't show the proper formatting although the code tags are there. Changing to the \ tag helped in this case, but it seems to be odd.
Edited by: Randolf Geist on Feb 23, 2009 11:28 AM
Odd behaviour of forum software