Re: What does Page Layout version mean? (Was: Re: Reducing NUMERIC size for 8.3)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: What does Page Layout version mean? (Was: Re: Reducing NUMERIC size for 8.3)
Date: 2007-06-19 14:15:50
Message-ID: 27263.1182262550@sss.pgh.pa.us
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Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM> writes:
> I'm little bit confused when we introduce new page layout version? I
> expect that new version become with changes with pageheader, tuple
> header or data encoding (varlen/TOAST ...). But in case when there is
> new data type internal implementation, there was not reason to update
> version (see inet/cidr between 8.1 -> 8.2). Can me somebody clarify this?

Well, we've changed it when there was a benefit to an existing tool to
do so. So far that's meant page header and tuple header changes. If
we ever had a working in-place upgrade solution, I think we'd be willing
to make the page version account for datatype format changes too.

regards, tom lane

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