Re: query very slow when enable_seqscan=on

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Tomasz Ostrowski <tometzky(at)batory(dot)org(dot)pl>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: query very slow when enable_seqscan=on
Date: 2006-07-04 18:15:54
Message-ID: 25494.1152036954@sss.pgh.pa.us
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-bugs pgsql-performance

Tomasz Ostrowski <tometzky(at)batory(dot)org(dot)pl> writes:
> So why estimate regex expressions if there is no estimation possible?
> Let's set this estimate to be pessimistic (match everything or
> everything not null) and it will choose better plans.

Better plans for this specific example, worse plans for other cases.
Life is not that simple.

regards, tom lane

In response to

Responses

Browse pgsql-bugs by date

  From Date Subject
Next Message Tom Lane 2006-07-04 20:17:45 Re: BUG #2512: pg_dump produces unrestorable output when table and serial sequence are not in the same schema
Previous Message tommaso gastaldi 2006-07-04 17:00:18 BUG #2513: What? OleDbSchemaGuids not supported ?!!! This is CRUCIAL!

Browse pgsql-performance by date

  From Date Subject
Next Message Gene 2006-07-04 20:27:44 Re: optimizing LIKE '%2345' queries
Previous Message tomas 2006-07-04 16:24:34 Re: query very slow when enable_seqscan=on