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Re: Posible planner improvement?

From: ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
To: Albert Cervera Areny <albert(at)sedifa(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Posible planner improvement?
Date: 2008-05-26 11:30:00
Message-ID: 20080526201825.C96D.52131E4D@oss.ntt.co.jp (view raw or flat)
Thread:
Lists: pgsql-performance
Hello Albert,

Albert Cervera Areny <albert(at)sedifa(dot)com> wrote:

> I've got a query similar to this:
> 
> select * from t1, t2 where t1.id > 158507 and t1.id = t2.id;
> 
> That took > 84 minutes (the query was a bit longer but this is the part that 
> made the difference) after a little change the query took ~1 second:
> 
> select * from t1, t2 where t1.id > 158507 and t2.id > 158507 and t1.id = 
> t2.id;

I had a similar problem here:
  http://archives.postgresql.org/pgsql-general/2007-02/msg00850.php
and added a redundant inequality explicitly to make it work well.

I think it is worth trying to improve, but I'm not sure we can do it
against user defined types. Does postgres always require transitive law
to all types?

Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center



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Subject: Re: [PERFORM] Posible planner improvement?

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