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

Re: Operator class group proposal

From: Gregory Stark <gsstark(at)mit(dot)edu>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Operator class group proposal
Date: 2006-12-22 21:21:25
Message-ID: 87tzznd3u2.fsf@stark.xeocode.com (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> No, what you'll get is something like
> 
> 	int4var::float8 float8eq float8var
> 
> which is perfectly mergejoinable ... however, it's not clear that the
> planner will make very good estimates about the value of the cast
> expression.  I'm not sure if it's worth introducing a pile more
> crosstype operators to change that situation --- improving
> the selectivity functions to handle casts better might be a wiser
> approach.

So the only reason we needed the cross-data-type operators was to get better
estimates? I thought without them you couldn't get an index-based plan at all.

-- 
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com


In response to

Responses

pgsql-hackers by date

Next:From: Greg SmithDate: 2006-12-22 21:33:43
Subject: Re: Load distributed checkpoint
Previous:From: Gregory StarkDate: 2006-12-22 21:13:49
Subject: Re: Load distributed checkpoint

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