Optimizer parameters different in 10053 trace

Question

Hello,
The optimizer settings and the ones reported in the 10053 trace does not match. Is this a known issue ? Version is printed in the code snippet.
Here, optimizer_mode is set to ALL_ROWS, but 10053 trace reports this as first_rows_100. Similarly, optimizer_index_cost_adj is 1. But, it is 25 in the trace.
The query is not using hints.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production With the Partitioning, Real Application Clusters, OLAP and Data Mining options
SQL> show parameter opti
NAME                                 TYPE        VALUE
filesystemio_options                 string      none
object_cache_optimal_size            integer     102400
optimizer_dynamic_sampling           integer     2
optimizer_features_enable            string      10.2.0.3
optimizer_index_caching              integer     100
optimizer_index_cost_adj             integer     1
optimizer_mode                       string      ALL_ROWS
optimizer_secure_view_merging        boolean     TRUE
plsql_optimize_level                 integer     2
SQL>Contents of 10053 trace
PARAMETERS USED BY THE OPTIMIZER
  PARAMETERS WITH ALTERED VALUES
  sort_area_retained_size             = 65535
  optimizer_mode                      = first_rows_100
  optimizer_index_cost_adj            = 25
  optimizer_index_caching             = 100
  *********************************I can see the same used in here..
Content of other_xml column
===========================
  db_version     : 10.2.0.3
  parse_schema   : COT_PLUS
  plan_hash      : 733167152
  Outline Data:
  /*+
    BEGIN_OUTLINE_DATA
      IGNORE_OPTIM_EMBEDDED_HINTS
      OPTIMIZER_FEATURES_ENABLE('10.2.0.3')
      OPT_PARAM('optimizer_index_cost_adj' 25)
      OPT_PARAM('optimizer_index_caching' 100)
      FIRST_ROWS(100)
      OUTLINE_LEAF(@"SEL$5DA710D3")
      UNNEST(@"SEL$2")
      OUTLINE(@"SEL$1")
      OUTLINE(@"SEL$2")
      FULL(@"SEL$5DA710D3" "CDW"@"SEL$1")
      INDEX_RS_ASC(@"SEL$5DA710D3" "O"@"SEL$2" ("ORDERS"."STATUS_ID"))
      LEADING(@"SEL$5DA710D3" "CDW"@"SEL$1" "O"@"SEL$2")
      USE_NL(@"SEL$5DA710D3" "O"@"SEL$2")
    END_OUTLINE_DATA
  */Rgds,
Gokul
Edited by: Gokul Gopal on 13-Jun-2012 03:14

Answer 1

Gokul,
Please report the output of the following, which checks the V$SES_OPTIMIZER_ENV view for the current session:
SELECT
  NAME,
  VALUE,
  ISDEFAULT
FROM
  V$SES_OPTIMIZER_ENV
WHERE
  SID=(SELECT SID FROM V$MYSTAT WHERE ROWNUM=1)
  AND NAME IN ('optimizer_mode','optimizer_index_cost_adj','optimizer_index_caching')
ORDER BY
  NAME;In the same session, execute the following (your SQL statement with 1=1 added in the WHERE clause to produce a hard parse):
ALTER SESSION SET TRACEFILE_IDENTIFIER='OPTIMIZER_TEST';
ALTER SESSION SET EVENTS '10053 TRACE NAME CONTEXT FOREVER, LEVEL 1';
select * from A where 1=1 AND col1 = (select to_char(col1) from B where status in (16,12,22));
ALTER SESSION SET EVENTS '10053 TRACE NAME CONTEXT OFF';Take a look in the generated 10053 trace file. Are the values for the optimizer_mode, optimizer_index_cost_adj, and optimizer_index_caching found in the OPTIMIZER_TEST 10053 trace file the same as what was produced by the above select from V$SES_OPTIMIZER_ENV?
Charles Hooper
http://hoopercharles.wordpress.com/
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc.