Re: Question regarding the database page layout.

From: Gregory Stark <stark(at)enterprisedb(dot)com>
To: "Ryan Bradetich" <rbradetich(at)gmail(dot)com>
Cc: "pgsql-hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Question regarding the database page layout.
Date: 2008-08-11 09:24:31
Message-ID: 878wv3ucog.fsf@oxford.xeocode.com
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"Ryan Bradetich" <rbradetich(at)gmail(dot)com> writes:

> After a cursory glance at the HeapTupleHeaderData structure, it appears it
> could be aligned with INTALIGN instead of MAXALIGN. The one structure I was
> worried about was the 6 byte t_ctid structure. The comments in
> src/include/storage/itemptr.h file indicate the ItemPointerData structure is
> composed of 3 int16 fields. So everthing in the HeapTupleHeaderData
> structure is 32-bits or less.

Sure, but the tuple itself could contain something with double alignment. If
you have a bigint or double in the tuple then heap_form_tuple needs to know
where to put it so it ends up at right alignment.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's Slony Replication support!

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