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

Re: Performance penalty of visibility info in indexes?

From: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
To: "Jim Nasby" <decibel(at)decibel(dot)org>
Cc: "PostgreSQL Development" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Performance penalty of visibility info in indexes?
Date: 2007-02-02 19:41:26
Message-ID: 1170445286.3645.68.camel@silverbirch.site (view raw or flat)
Thread:
Lists: pgsql-hackers
On Thu, 2007-02-01 at 23:57 -0600, Jim Nasby wrote:
> Has anyone actually measured the performance overhead of storing  
> visibility info in indexes? I know the space overhead sounds  
> daunting, but even if it doubled the size of the index in many cases  
> that'd still be a huge win over having to scan the heap as well as  
> the index (esp. for things like count(*)). There would also be  
> overhead from having to update the old index tuple, but for the case  
> of updates you're likely to need that page for the new index tuple  
> anyway.
> 
> I know this wouldn't work for all cases, but ISTM there are many  
> cases where it would be a win.

It would prevent any optimization that sought to avoid inserting rows
into the index each time we perform an UPDATE. Improving UPDATE
performance seems more important than improving count(*), IMHO.

-- 
  Simon Riggs             
  EnterpriseDB   http://www.enterprisedb.com



In response to

Responses

pgsql-hackers by date

Next:From: Tom LaneDate: 2007-02-02 20:11:55
Subject: Proposed adjustments in MaxTupleSize and toast thresholds
Previous:From: Simon RiggsDate: 2007-02-02 19:30:01
Subject: Re: Referential Integrity and SHARE locks

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