Re: BUG #6426: Complex query runs 10 times longer with "LIMIT 20" - Mailing list pgsql-bugs

From Andrew Schetinin
Subject Re: BUG #6426: Complex query runs 10 times longer with "LIMIT 20"
Date
Msg-id CA+fUw71dQu9enLViyHnMfe7i2ChwJXUKcVWPg6bdsN_NwMvBcg@mail.gmail.com
Whole thread Raw
In response to Re: BUG #6426: Complex query runs 10 times longer with "LIMIT 20"  (Alex Lai <alai@sesda2.com>)
Responses Re: BUG #6426: Complex query runs 10 times longer with "LIMIT 20"
List pgsql-bugs
Hi Alex,

Thank you. I played with subqueries, but in this case I did not see a good
enough improvement.

In my specific case, what I've seen from the query execution plans, is that
without LIMIT the query uses Hash Joins, but once I add LIMIT, it starts
using Nested Loop Joins almost everywhere.

Regards,

Andrew

On Wed, Feb 1, 2012 at 9:42 PM, Alex Lai <alai@sesda2.com> wrote:

> Hi Andrew,
> I posted for another post, its may give you a workaround.
> I still not fully understand how PG choose execute plan that slow down so
> much.
>
> I had the same situation in one of my query.
> Use the subquery can speed up almost by 100 times faster.
>
> ..........
>


> Hope this help.
>
>
> Best Regards,
> Alex Lai
>
> --
> Best regards,
>
>
> Alex Lai
> OMI SIPS DBA ADNET Systems , Inc. 7515 Mission Drive, Suite A100 Lanham,
> MD 20706 301-352-4657 (phone) 301-352-0437 (fax) alai@sesda2.com
>
>


--
--
Andrew Schetinin

pgsql-bugs by date:

Previous
From: Alex Lai
Date:
Subject: Re: BUG #6426: Complex query runs 10 times longer with "LIMIT 20"
Next
From: Duncan Rance
Date:
Subject: Re: BUG #6425: Bus error in slot_deform_tuple