Re: slow queries, possibly disk io
От | Josh Close |
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Тема | Re: slow queries, possibly disk io |
Дата | |
Msg-id | 4a0cafe205052707541373ab8a@mail.gmail.com обсуждение исходный текст |
Ответ на | Re: slow queries, possibly disk io (Tom Lane <tgl@sss.pgh.pa.us>) |
Список | pgsql-performance |
> I think you really want that seqscan to be an indexscan, instead. > I'm betting this is PG 7.4.something? If so, probably the only > way to make it happen is to simplify the now() expression to a constant: > > SELECT COALESCE( SUM( iNumSent ), 0 ) AS iNumSent > FROM adaption.tblBatchHistory_\' || this_rServerIds.iId || \' > WHERE tStamp > \\\'' || (now() - interval \'5 mins\')::text || > \'\\\'\'; The dollar sign thing would be a lot easier. I can't get this to work. I'm using a db manager where I can just use ' instead of \'. How would it look for that? In other words, it doesn't have the "create or replace function as ' --stuff ' language 'plpgsql'" it just has the actual function. Makes things a little easier. I'm getting an error at or near "5". > > because pre-8.0 the planner won't realize that the inequality is > selective enough to favor an indexscan, unless it's comparing to > a simple constant. > > (BTW, 8.0's dollar quoting makes this sort of thing a lot less painful) > > regards, tom lane > -- -Josh
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