Обсуждение: Forcing use of a particular index

http://www.postgresql.org/docs/8.0/static/indexes-examine.html

Says:

"If you do not succeed in adjusting the costs to be more
appropriate, then you may have to resort to forcing index
usage explicitly."

Is there a way to force a query to use a particular index?
If not, what does this sentence mean?

Thanks.


Karl <kop@meme.com>
Free Software:  "You don't pay back, you pay forward."
                  -- Robert A. Heinlein

Hi,

At 01:16 28/06/2005, Karl O. Pinc wrote:
>http://www.postgresql.org/docs/8.0/static/indexes-examine.html
>
>Says:
>
>"If you do not succeed in adjusting the costs to be more
>appropriate, then you may have to resort to forcing index
>usage explicitly."
>
>Is there a way to force a query to use a particular index?

Not that I know of.

>If not, what does this sentence mean?

That you can force the planner to use an index (any one) over not using an
index (and using seq scans instead) by setting enable_seqscan to off.

Jacques.