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#1 (**permalink**) 04-18-2008, 11:55 AM

Yves Vindevogel <yves.vindevogel@implements.be> writes:
> Can anyone explain me this ?

> rvponp=# explain select * from tblprintjobs order by loginuser,
> desceventdate, desceventtime offset 25 limit 25 ;
> QUERY PLAN
> ------------------------------------------------------------------------
> -----------
> Limit (cost=349860.62..349860.68 rows=25 width=206)
> -> Sort (cost=349860.56..351416.15 rows=622236 width=206)
> Sort Key: loginuser, desceventdate, desceventtime
> -> Seq Scan on tblprintjobs (cost=0.00..25589.36 rows=622236 width=206)
> (4 rows)

Do you have an index matching that sort key? I'd certainly expect the
above to use it if it were there. For the full table case it's not so
clear --- an indexscan isn't always better.

regards, tom lane

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#2 (**permalink**) 04-18-2008, 11:55 AM

Yves Vindevogel <yves.vindevogel@implements.be> writes:
> create index ixPrintjobsLoginDescEventdateDesceventtime on
> tblPrintjobs (loginuser, desceventdate, desceventtime) ;

Hmm, that certainly looks like it should match the query. What happens
to the EXPLAIN output if you do "set enable_sort = false"?

regards, tom lane

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Re: Limit clause not using index