From: Heikki Linnakangas <heikki@enterprisedb.com>
To: Zdenek Kotala <Zdenek.Kotala@Sun.COM>
Cc: Pavan Deolasee <pavan.deolasee@gmail.com>
Cc: PostgreSQL-patches <pgsql-patches@postgresql.org>
Subject: Re: page macros cleanup
Date: Fri, 04 Jul 2008 14:18:37 +0300
Message-ID: <486E070D.8010101@enterprisedb.com> (raw)
In-Reply-To: <486E008F.3080304@sun.com>
References: <48529B83.9010907@sun.com>
<2e78013d0807030450m4cab60d0jd99d1acce59fae56@mail.gmail.com>
<486DD1D1.50604@sun.com>
<2e78013d0807040150w393ad72codaf06a6ac12a83ce@mail.gmail.com>
<486DF644.4070604@enterprisedb.com>
<486E008F.3080304@sun.com>
Zdenek Kotala wrote:
> By my opinion first place where tuple should be placed is:
>
> MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData))
Yeah, but we don't enforce that directly. We enforce it by MAXALIGNing
size in PageAddItem, and with the rule that special-size is MAXALIGNed.
To put it another way, it's possible that there's an unaligned amount of
free space on a page, as returned by PageGetExactFreeSpace. But since
item size is always MAXALIGNed, it's impossible to use it all.
Come to think of it, why do we require MAXALIGN alignment of tuples? I
must be missing something, but AFAICS the widest fields in
HeapTupleHeaderData are 4-bytes wide, so it should be possible to get
away with 4-byte alignment.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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-patches@postgresql.org
Cc: heikki@enterprisedb.com, Zdenek.Kotala@Sun.COM, pavan.deolasee@gmail.com
Subject: Re: page macros cleanup
In-Reply-To: <486E070D.8010101@enterprisedb.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