Using index with order desc
От | Dave Smith |
---|---|
Тема | Using index with order desc |
Дата | |
Msg-id | 1026851718.4483.56.camel@playpen обсуждение исходный текст |
Ответы |
Re: Using index with order desc
Re: Using index with order desc |
Список | pgsql-general |
Using pg 7.2.1 If I have a simple table transfer company_id int, module character(2) otherfields ... and an index CREATE INDEX transfer_5 on transfer(company_id,module); with the query explain select * from transfer where company_id=1012 order by company_id,module desc; I get .. NOTICE: QUERY PLAN: Sort (cost=462.74..462.74 rows=117 width=176) -> Index Scan using transfer_5 on transfer (cost=0.00..458.71 rows=117 width=176) Other info .. select count(*) from transfer where company_id=1012; count ------- 5264 (1 row) import=# select count(*) from transfer; count ------- 23481 (1 row) Why does it have to sort it? The desc is at the end and the first argument is constant. Is there some way I can force postgres to read the index backwards and save the sort step?
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