Re: Index Choice Problem

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Adam Alkins <adam.alkins@xxxxxxxxx> writes:
> SELECT t.topic_id
> 			FROM phpbb_topics AS t
> 				WHERE t.forum_id = 71
> 					AND t.topic_id NOT IN (205026, 29046, 144569, 59780, 187424,
> 138635, 184973, 170551, 22419, 181690, 197254, 205130)
> 						ORDER BY t.topic_last_post_time DESC
> 							LIMIT 23 OFFSET 0

If you're using 8.1, you'd probably find that an index on (forum_id,
topic_last_post_time) would work nicely for this.  You could use it
in prior versions too, but you'd have to spell the ORDER BY rather
strangely:
	ORDER BY forum_id desc, topic_last_post_time desc
The reason for this trickery is to get the planner to realize that
the index order matches the ORDER BY ...

			regards, tom lane


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