Re: any way to use indexscan to get last X values
От | Shridhar Daithankar |
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Тема | Re: any way to use indexscan to get last X values |
Дата | |
Msg-id | 3EEDADF0.29611.3901BC1@localhost обсуждение исходный текст |
Ответ на | Re: any way to use indexscan to get last X values (Tomaz Borstnar <tomaz.borstnar@over.net>) |
Ответы |
Re: any way to use indexscan to get last X values
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Список | pgsql-performance |
On 16 Jun 2003 at 0:37, Tomaz Borstnar wrote: > > krtjavendan34=> EXPLAIN ANALYZE SELECT thread, modifystamp, count(id) AS > tcount,abstime(modifystamp) AS latest, max(id) as maxid FROM tjavendan > WHERE approved='Y' GROUP BY modifystamp, thread ORDER BY modifystamp desc, > thread desc limit 40; > QUERY > PLAN > ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ > Limit (cost=0.00..97.13 rows=40 width=12) (actual time=1.07..48.71 > rows=40 loops=1) > -> Aggregate (cost=0.00..20947.38 rows=8626 width=12) (actual > time=1.05..48.23 rows=41 loops=1) > -> Group (cost=0.00..20516.06 rows=86265 width=12) (actual > time=0.35..42.25 rows=843 loops=1) > -> Index Scan Backward using tjavendan_modstamp_thrd on > tjavendan (cost=0.00..20084.73 rows=86265 width=12) (actual > time=0.34..31.29 rows=844 loops=1) > Filter: (approved = 'Y'::bpchar) > Total runtime: 50.20 msec > (6 rows) > > Used to be between 5800 and 6741 msec before this patch! Good that the patch works for you. But as I see there is an improvement in plan. Not nitpicking but what does actual performance difference between system before patch and after patch? Bye Shridhar -- QOTD: "In the shopping mall of the mind, he's in the toy department."
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