Re: Order by optimisations?
От | Christopher Kings-Lynne |
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Тема | Re: Order by optimisations? |
Дата | |
Msg-id | 42D74CCE.3030609@familyhealth.com.au обсуждение исходный текст |
Ответ на | Re: Order by optimisations? (Tom Lane <tgl@sss.pgh.pa.us>) |
Список | pgsql-hackers |
> Well, date evidently isn't the high-order key of this index. But why > exactly are you worried about a sort of 2 rows? Aha that's nailed it: usa=> explain select * from users_myfoods_map where user_id=1 and date between '2003-11-03' and '2003-11-03' order by user_id, date; QUERY PLAN ------------------------------------------------------------------------------------------------------------- Index Scanusing users_myfoods_map_user_id_date_key on users_myfoods_map (cost=0.00..3.78 rows=1 width=22) Index Cond: ((user_id = 1) AND (date >= '2003-11-03'::date) AND (date <= '2003-11-03'::date)) (2 rows) I don't care about this particular result. But imagine it running thousands of times a minute, with result sets between 0 and 50 rows... Chris
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