Re: What's the difference between SET STORAGE MAIN and EXTENDED?

From: Zoltan Boszormenyi <zb(at)cybertec(dot)at>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: What's the difference between SET STORAGE MAIN and EXTENDED?
Date: 2007-09-07 15:22:06
Message-ID: 46E16C9E.2080007@cybertec.at
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Tom Lane írta:
> Zoltan Boszormenyi <zb(at)cybertec(dot)at> writes:
>
>> At the end of the day, the behaviour is the same, isn't it?
>>
>
> No, there's a difference in terms of the priority for pushing this
> column out to toast storage, versus pushing other columns of the row
> out to toast. Normally we push the widest (remaining) column out,
> and repeat, until the tuple is small enough. But MAIN columns stay
> in, until there are no EXTENDED columns left.
>
> regards, tom lane
>

Thanks very much for clarifying.

I was thinking of a binary data that wouldn't fit
into the maximum inline tuple size. In this case
both MAIN and EXTENDED end up compressed
and out-of-line. I didn't consider having multiple
bytea or text columns filled with small amount of data.

Best regards,
Zoltán Böszörményi

--
----------------------------------
Zoltán Böszörményi
Cybertec Geschwinde & Schönig GmbH
http://www.postgresql.at/

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