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

Re: estimating # of distinct values

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Tomas Vondra <tv(at)fuzzy(dot)cz>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: estimating # of distinct values
Date: 2010-12-31 02:02:04
Message-ID: 15389.1293760924@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> I was thinking that we could have two different ANALYZE modes, one
> "full" and one "incremental"; autovacuum could be modified to use one or
> the other depending on how many changes there are (of course, the user
> could request one or the other, too; not sure what should be the default
> behavior).

How is an incremental ANALYZE going to work at all?  It has no way to
find out the recent changes in the table, for *either* inserts or
deletes.  Unless you want to seqscan the whole table looking for tuples
with xmin later than something-or-other ... which more or less defeats
the purpose.

			regards, tom lane

In response to

Responses

pgsql-hackers by date

Next:From: Tom LaneDate: 2010-12-31 02:04:11
Subject: Re: Old git repo
Previous:From: Tom LaneDate: 2010-12-31 01:58:20
Subject: Re: and it's not a bunny rabbit, either

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