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WAL logging freezing

From: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
To: pgsql-patches(at)postgresql(dot)org
Subject: WAL logging freezing
Date: 2006-10-24 07:20:13
Message-ID: 453DBEAD.3080201@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
Here's a patch for WAL logging tuple freezes in vacuum, per discussion
on pgsql-bugs.

This patch is against CVS head. Should this be backported to stable
branches? I think it should.

After writing the patch, I realized that it needs some thought if 
backported, because WAL records of removing tuples and freezing tuples 
share the same heapam opcode XLOG_HEAP_CLEAN, and are only 
differentiated by setting a flag. If we applied the patch as it is, and 
for some reason someone replayed a WAL log generated by a newer version, 
with the patch, with an older version, without the patch, the older 
version would interpret the freeze WAL records as dead tuple removals, 
and remove live records. I would've liked to give freezing a new opcode, 
  but we've ran out of them (see htup.h).

-- 
    Heikki Linnakangas
    EnterpriseDB   http://www.enterprisedb.com


Attachment: logfreezes.diff
Description: text/plain (11.9 KB)

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