Re: opportunistic tuple freezing

From: Jeff Davis <pgsql(at)j-davis(dot)com>
To: Greg Stark <gsstark(at)mit(dot)edu>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: opportunistic tuple freezing
Date: 2009-08-17 04:01:40
Message-ID: 1250481700.24704.17.camel@jdavis
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On Mon, 2009-08-17 at 04:01 +0100, Greg Stark wrote:
> If it's convenient to have a function to handle the scan then use it
> for both scans. You could have a flag that indicates it should abort
> after the first freeze. I think it would be simpler to have a return
> value indicating the oldest transaction found and then just call it
> again if that's old enough for the opportunistic threshold.

Thanks for the suggestions.

I think it will take some significant refactoring. It needs to work from
both scan_heap and lazy_scan_heap, so I would need to make a loop that
works for both of those cases. Additionally, the second scan needs to
avoid all of the side effects (like double-counting), which might mean
some ugly branching. For instance, the big switch statement is
completely unnecessary during the second scan.

I'll come up with a refactored version of the patch.

Jeff Davis

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