Comments on: Ignoring hints http://jonathanlewis.wordpress.com/2011/01/16/ignoring-hints-4/ Just another Oracle weblog Fri, 17 May 2013 13:58:17 +0000 hourly 1 http://wordpress.com/ By: Valentin Nikotin http://jonathanlewis.wordpress.com/2011/01/16/ignoring-hints-4/#comment-44806 Tue, 31 Jan 2012 14:19:39 +0000 http://jonathanlewis.wordpress.com/?p=5562#comment-44806 Here is a little note about the hinting: http://valentinnikotin.com/2012/01/31/comments-in-hint/

]]> By: Martin Preiss http://jonathanlewis.wordpress.com/2011/01/16/ignoring-hints-4/#comment-39225 Wed, 19 Jan 2011 08:54:03 +0000 http://jonathanlewis.wordpress.com/?p=5562#comment-39225 Jonathan,
in his comment to Charles Hooper’s post Kerry Osborne gives the advice to separate hints from other comments – and this sounds convincing to me. On the other side I remember that Randolf Geist recently explained that “there are cases/environments where comments are stripped prior to execution” (with the example of PL/SQL). Do think it’s a good idea to separate hints from other comments? Or do you think it is save to add comments inside a hint (after the hint-Keywords)?

]]> By: Martin Preiss http://jonathanlewis.wordpress.com/2011/01/16/ignoring-hints-4/#comment-39224 Wed, 19 Jan 2011 08:38:19 +0000 http://jonathanlewis.wordpress.com/?p=5562#comment-39224 Todor,
the MOS-Bug is indeed named “Bug 8432870: NOLOGGING HINT IN 10G CAUSES HINTS AFTER IT TO BE IGNORED” – and there is an example similar to the one you provide.

]]> By: David Aldridge http://jonathanlewis.wordpress.com/2011/01/16/ignoring-hints-4/#comment-39202 Mon, 17 Jan 2011 11:18:22 +0000 http://jonathanlewis.wordpress.com/?p=5562#comment-39202 It’s getting difficult to avoid using SQL keywords. With 1,144 to choose from in 10.2.0.4 you could have a pretty good game of Scrabble with them.

“SQL Keyword Scrabble” would be a pretty good team game for a conference. “Blank”,A,B,E,N,M,Q … anyone?

]]> By: Todor Botev http://jonathanlewis.wordpress.com/2011/01/16/ignoring-hints-4/#comment-39201 Mon, 17 Jan 2011 09:01:05 +0000 http://jonathanlewis.wordpress.com/?p=5562#comment-39201 Could it be that only the hints AFTER the SQL keyword get ignored? I made the following quick example inserting the word NOLOGGING to different places in the hint:

09:34:16 SQL> create table t1 (n number);

Tabelle wurde erstellt.

09:34:33 SQL> create table t2 (n number);

Tabelle wurde erstellt.

09:34:42 SQL> set autotrace traceonly explain

09:34:54 SQL> select /*+ NOLOGGING parallel(t1,4) parallel(t2,4) */ * from t1, t2;

Ausführungsplan
----------------------------------------------------------
Plan hash value: 787647388

-----------------------------------------------------------------------------
| Id  | Operation            | Name | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------
|   0 | SELECT STATEMENT     |      |     1 |    26 |     4   (0)| 00:00:01 |
|   1 |  MERGE JOIN CARTESIAN|      |     1 |    26 |     4   (0)| 00:00:01 |
|   2 |   TABLE ACCESS FULL  | T1   |     1 |    13 |     2   (0)| 00:00:01 |
|   3 |   BUFFER SORT        |      |     1 |    13 |     2   (0)| 00:00:01 |
|   4 |    TABLE ACCESS FULL | T2   |     1 |    13 |     2   (0)| 00:00:01 |
-----------------------------------------------------------------------------


09:37:51 SQL> select /*+ parallel(t1,4) NOLOGGING parallel(t2,4) */ * from t1, t2;

Ausführungsplan
----------------------------------------------------------
Plan hash value: 3248347947

------------------------------------------------------------------------------------------------------------------
| Id  | Operation                | Name     | Rows  | Bytes | Cost (%CPU)| Time     |    TQ  |IN-OUT| PQ Distrib |
------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT         |          |     1 |    26 |     5   (0)| 00:00:01 |        |      |            |
|   1 |  PX COORDINATOR          |          |       |       |            |          |        |      |            |
|   2 |   PX SEND QC (RANDOM)    | :TQ10001 |     1 |    26 |     5   (0)| 00:00:01 |  Q1,01 | P->S | QC (RAND)  |
|   3 |    MERGE JOIN CARTESIAN  |          |     1 |    26 |     5   (0)| 00:00:01 |  Q1,01 | PCWP |            |
|   4 |     SORT JOIN            |          |       |       |            |          |  Q1,01 | PCWP |            |
|   5 |      PX BLOCK ITERATOR   |          |     1 |    13 |     2   (0)| 00:00:01 |  Q1,01 | PCWC |            |
|   6 |       TABLE ACCESS FULL  | T1       |     1 |    13 |     2   (0)| 00:00:01 |  Q1,01 | PCWP |            |
|   7 |     BUFFER SORT          |          |     1 |    13 |     3   (0)| 00:00:01 |  Q1,01 | PCWP |            |
|   8 |      BUFFER SORT         |          |       |       |            |          |  Q1,01 | PCWC |            |
|   9 |       PX RECEIVE         |          |     1 |    13 |     2   (0)| 00:00:01 |  Q1,01 | PCWP |            |
|  10 |        PX SEND BROADCAST | :TQ10000 |     1 |    13 |     2   (0)| 00:00:01 |        | S->P | BROADCAST  |
|  11 |         TABLE ACCESS FULL| T2       |     1 |    13 |     2   (0)| 00:00:01 |        |      |            |
------------------------------------------------------------------------------------------------------------------

09:37:53 SQL> select /*+ parallel(t1,4) parallel(t2,4) NOLOGGING */ * from t1, t2;

Ausführungsplan
----------------------------------------------------------
Plan hash value: 1997482048

------------------------------------------------------------------------------------------------------------------
| Id  | Operation                | Name     | Rows  | Bytes | Cost (%CPU)| Time     |    TQ  |IN-OUT| PQ Distrib |
------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT         |          |     1 |    26 |     5   (0)| 00:00:01 |        |      |            |
|   1 |  PX COORDINATOR          |          |       |       |            |          |        |      |            |
|   2 |   PX SEND QC (RANDOM)    | :TQ10001 |     1 |    26 |     5   (0)| 00:00:01 |  Q1,01 | P->S | QC (RAND)  |
|   3 |    MERGE JOIN CARTESIAN  |          |     1 |    26 |     5   (0)| 00:00:01 |  Q1,01 | PCWP |            |
|   4 |     SORT JOIN            |          |       |       |            |          |  Q1,01 | PCWP |            |
|   5 |      PX RECEIVE          |          |     1 |    13 |     2   (0)| 00:00:01 |  Q1,01 | PCWP |            |
|   6 |       PX SEND BROADCAST  | :TQ10000 |     1 |    13 |     2   (0)| 00:00:01 |  Q1,00 | P->P | BROADCAST  |
|   7 |        PX BLOCK ITERATOR |          |     1 |    13 |     2   (0)| 00:00:01 |  Q1,00 | PCWC |            |
|   8 |         TABLE ACCESS FULL| T1       |     1 |    13 |     2   (0)| 00:00:01 |  Q1,00 | PCWP |            |
|   9 |     BUFFER SORT          |          |     1 |    13 |     3   (0)| 00:00:01 |  Q1,01 | PCWP |            |
|  10 |      PX BLOCK ITERATOR   |          |     1 |    13 |     2   (0)| 00:00:01 |  Q1,01 | PCWC |            |
|  11 |       TABLE ACCESS FULL  | T2       |     1 |    13 |     2   (0)| 00:00:01 |  Q1,01 | PCWP |            |
------------------------------------------------------------------------------------------------------------------

09:38:08 SQL>
]]> By: Gary http://jonathanlewis.wordpress.com/2011/01/16/ignoring-hints-4/#comment-39196 Sun, 16 Jan 2011 22:42:22 +0000 http://jonathanlewis.wordpress.com/?p=5562#comment-39196 Thanks for the highlight. Worth adding that, although it has a bug number, it has been deemed to be “Not a Bug”.

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