Comments on: my query is not using my index http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html Oracle Certified Master Sun, 07 Sep 2008 06:07:29 +0000 http://wordpress.org/?v=2.0.5 by: Laurent Schneider http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5614 Sat, 15 Dec 2007 06:53:00 +0000 http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5614 Sure, I would love to speak Chinese, I did got help on that one :-D Sure, I would love to speak Chinese, I did got help on that one :-D

]]> by: Kamus http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5610 Fri, 14 Dec 2007 17:55:52 +0000 http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5610 @Laurent I found this in in your site: Language : * French * German * English * 在家,我不说英语 The last row is Chinese, so I think .... @Laurent
I found this in in your site:
Language :
* French
* German
* English
* 在家,我不说英语
The last row is Chinese, so I think ….

]]> by: Laurent Schneider http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5609 Fri, 14 Dec 2007 17:40:36 +0000 http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5609 No, I cannot speak Chinese neither and my wife speaks Bakossi ;-) Anyway, nice to know you too :!: No, I cannot speak Chinese neither and my wife speaks Bakossi ;-)

Anyway, nice to know you too :!:

]]> by: Kamus http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5608 Fri, 14 Dec 2007 17:17:50 +0000 http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5608 @Laurent so ... you just can speak Chinese? same as Eddie Awad, has a wife who make you speak Chinese? lol anyway, nice 2 cu @Laurent
so … you just can speak Chinese? same as Eddie Awad, has a wife who make you speak Chinese? lol
anyway, nice 2 cu

]]> by: Laurent Schneider http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5607 Fri, 14 Dec 2007 16:47:52 +0000 http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5607 LOL, I managed to register on itpub.net, but it is pure luck because I cannot read Chinese 8-) <a href="http://www.itpub.net/viewpro.php?uid=11252990" rel="nofollow">my itpub profile</a> LOL, I managed to register on itpub.net, but it is pure luck because I cannot read Chinese 8-)
my itpub profile

]]> by: Kamus http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5605 Fri, 14 Dec 2007 15:42:08 +0000 http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5605 Laurent, It seems you good at Chinese, so ... maybe you wanna meet some Oracle ACE from China. or you can visit our biggest oracle forum in China www.itpub.net I'm an Oracle ACE from Oracle corp. in China. Laurent, 意外发现你的blog，似乎你是懂得中文的，因此，也许你愿意认识更多来自中国的Oracle ACE。我们在维护全中国最大的Oracle论坛www.itpub.net。非常高兴认识你。 Laurent,

It seems you good at Chinese, so … maybe you wanna meet some Oracle ACE from China. or you can visit our biggest oracle forum in China www.itpub.net

I’m an Oracle ACE from Oracle corp. in China.

Laurent,
意外发现你的blog，似乎你是懂得中文的，因此，也许你愿意认识更多来自中国的Oracle ACE。我们在维护全中国最大的Oracle论坛www.itpub.net。非常高兴认识你。

]]> by: Coskan http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5599 Thu, 13 Dec 2007 17:06:49 +0000 http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5599 @Garry You get the index fast full scan because of the coumns you select. If you select r and t columns together you would probably get full table scan but when you just select r column CBO thinks that it is better to go index because selected columns are already indexed. @Garry

You get the index fast full scan because of the coumns you select.

If you select r and t columns together you would probably get full table scan

but when you just select r column CBO thinks that it is better to go index because selected columns are already indexed.

]]> by: CJ http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5598 Thu, 13 Dec 2007 16:47:27 +0000 http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5598 Interesting that CBO doesn't consider cost in the SELECT statement in the above example, but seems to consider it in the UPDATE statement given below: UPDATE t SET r = NULL WHERE r != 1; The plan should give an indexed full scan directly without hinting etc. Not sure if this behaviour changes in 11g, because I don't see why the optimizer should ignore costs in the SELECT statement. Regards, Charu. Interesting that CBO doesn’t consider cost in the SELECT statement in the above example, but seems to consider it in the UPDATE statement given below:

UPDATE t SET r = NULL WHERE r != 1;

The plan should give an indexed full scan directly without hinting etc.

Not sure if this behaviour changes in 11g, because I don’t see why the optimizer should ignore costs in the SELECT statement.

Regards,
Charu.

]]> by: Gary http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5589 Tue, 11 Dec 2007 19:29:07 +0000 http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5589 With XE and dbms_stats.gather_table_stats(user,'T',cascade=>true, method_opt=>'for all columns size skewonly'); I could get an INDEX FAST FULL SCAN/INDEX RANGE SCAN use with select r,t from t where r in (select r from t where r!=1); But it does look like that the optimizer won't got for the best plan for the plain query without a hint. With XE and
dbms_stats.gather_table_stats(user,’T',cascade=>true,
method_opt=>’for all columns size skewonly’);

I could get an INDEX FAST FULL SCAN/INDEX RANGE SCAN use with
select r,t from t where r in (select r from t where r!=1);

But it does look like that the optimizer won’t got for the best plan for the plain query without a hint.

]]> by: Laurent Schneider http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5588 Tue, 11 Dec 2007 15:21:51 +0000 http://laurentschneider.com/wordpress/2007/12/my-query-is-not-using-my-index.html#comment-5588 @Jens : yes, I should have written that CONNECT BY PRIOR is not supported 8-) but it was so easy to generate 1 million rows... unfortunately I did it with system as default tablespace and my system tablespace was suddenly 12 Gb... @Don : I rewrite your message because this stupid wordpress engine expect you to write &lt; and not < :-( well, the case is different as I am not using count (where full table scan is used), but I select also a non-index column and I want a TABLE ACCESS BY INDEX ROWID (that I did get only with a hint) @Jens : yes, I should have written that CONNECT BY PRIOR is not supported 8-) but it was so easy to generate 1 million rows… unfortunately I did it with system as default tablespace and my system tablespace was suddenly 12 Gb…

@Don : I rewrite your message because this stupid wordpress engine expect you to write &lt; and not < :-( well, the case is different as I am not using count (where full table scan is used), but I select also a non-index column and I want a TABLE ACCESS BY INDEX ROWID (that I did get only with a hint)

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