Re: Remove xmin and cmin from frozen tuples

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От Josh Berkus
Тема Re: Remove xmin and cmin from frozen tuples
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Msg-id 200509021335.43256.josh@agliodbs.com
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Ответ на Re: Remove xmin and cmin from frozen tuples  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: Remove xmin and cmin from frozen tuples  (Alvaro Herrera <alvherre@alvh.no-ip.org>)
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People:

> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Considering the cost/benefits, rather than doing some optimization for
> > long-lived tuples, I would like to see us merge the existing
> > xmin/xmax/cmin/cmax values back into three storage fields like we had
> > in 7.4 and had to expand to a full four in 8.0 to support
> > subtransactions.

Hmmm.   I personally don't see a whole lot of value in trimming 4 bytes per 
row off an archive table, particularly if the table would need to go 
through some kind of I/O intensive operation to do it.

Where I do see value is in enabling index-only access for "frozen" tables.  
That would be a *huge* gain, especially with bitmaps.   I think we've 
discussed this before,though.

-- 
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco


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