From: Jim C. Nasby <jnasby@pervasive.com>
To: K C Lau <kclau60@netvigator.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: Why so slow?
Date: Tue, 2 May 2006 15:13:35 -0500
Message-ID: <20060502201334.GA97354@pervasive.com> (raw)
In-Reply-To: <6.2.1.2.0.20060429110036.02c01b98@localhost>
References: <20060428145842.GI97354@pervasive.com>
<BAY101-F3027DA179AC8CEE9FAAF77ADB20@phx.gbl>
<20060428190005.GA15689@wolff.to>
<6.2.1.2.0.20060429084119.05290438@localhost>
<19397.1146278368@sss.pgh.pa.us>
<6.2.1.2.0.20060429110036.02c01b98@localhost>
On Sat, Apr 29, 2006 at 11:18:10AM +0800, K C Lau wrote:
>
> At 10:39 06/04/29, Tom Lane wrote:
> >K C Lau <kclau60@netvigator.com> writes:
> >> Without knowing the internals, I have this simplistic idea: if Postgres
> >> maintains the current lowest transaction ID for all active
> >transactions, it
> >> probably could recycle dead tuples on the fly.
> >
> >[ yawn... ] Yes, we've heard that before. The hard part is getting rid
> >of index entries.
> >
> > regards, tom lane
>
> I apologize for simplistic ideas again. I presume that the equivalent tuple
> header information is not maintained for index entries. What if they are,
> probably only for the most commonly used index types to allow recycling
> where possible? The extra space required would be recycled too. It would
> probably also help save a trip to the tuple data pages to determine the
> validity of index entries during index scans.
You should read through the -hacker archives, most of this stuff has
been gone over multiple times.
Storing tuple header info in indexes would be a huge drawback, as it
would result in about 20 extra bytes per index entry.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: jnasby@pervasive.com, kclau60@netvigator.com, tgl@sss.pgh.pa.us
Subject: Re: Why so slow?
In-Reply-To: <20060502201334.GA97354@pervasive.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox