Skip site navigation (1) Skip section navigation (2)

Re: Posible planner improvement?

From: PFC <lists(at)peufeu(dot)com>
To: "Richard Huxton" <dev(at)archonet(dot)com>, "Luke Lonergan" <LLonergan(at)greenplum(dot)com>
Cc: albert(at)sedifa(dot)com, pgsql-performance(at)postgresql(dot)org
Subject: Re: Posible planner improvement?
Date: 2008-05-21 16:18:27
Message-ID: op.ubih81yvcigqcu@apollo13.peufeu.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
On Wed, 21 May 2008 15:09:49 +0200, Richard Huxton <dev(at)archonet(dot)com>  
wrote:

> Luke Lonergan wrote:
>> The problem is that the implied join predicate is not being
>> propagated.  This is definitely a planner deficiency.
>
> IIRC only equality conditions are propagated and gt, lt, between aren't.  
>   I seem to remember that the argument given was that the cost of  
> checking for the ability to propagate was too high for the frequency  
> when it ocurred.
>
> Of course, what was true for code and machines of 5 years ago might not  
> be so today.
>

	Suggestion : when executing a one-off sql statement, optimizer should try  
to offer "best effort while being fast" ; when making a plan that will be  
reused many times (ie PREPARE, functions...) planning time could be  
muuuuch longer...

In response to

pgsql-performance by date

Next:From: Albert Cervera ArenyDate: 2008-05-21 16:22:42
Subject: Re: Posible planner improvement?
Previous:From: Richard HuxtonDate: 2008-05-21 14:39:54
Subject: Re: "Big O" notation for postgres?

pgsql-hackers by date

Next:From: Albert Cervera ArenyDate: 2008-05-21 16:22:42
Subject: Re: Posible planner improvement?
Previous:From: Pavel StehuleDate: 2008-05-21 16:12:27
Subject: proposal: table functions and plpgsql

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group