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Re: Requesting clarification on Vacuuming/Freezing behaviour

From: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
To: Gokulakannan Somasundaram <gokul007(at)gmail(dot)com>
Cc: pgsql-hackers list <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Requesting clarification on Vacuuming/Freezing behaviour
Date: 2007-12-17 08:09:17
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Lists: pgsql-hackers
Gokulakannan Somasundaram wrote:
> a) When i was looking at the code for freezing heap tuples, i found out the
> following. While freezing we log the complete block(not just the tuples we
> froze).
> b) Again after removing the dead tuples and fragmentation, we log the
> complete block.

Umm, no we don't. In log_heap_freeze, we log an array of offsets, of 
those tuples that were frozen.

Perhaps you're been confused by full page writes? If a block hasn't been 
modified by last checkpoint, then we do log the whole page for any 
operation, including vacuuming and freezing. (except setting hint bits).

   Heikki Linnakangas

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