Forgot to attach the script I promised..

You need to set $PGDATA before running the script. And psql,pg_ctl and
pg_resetxlog need to be in $PATH. After running the script, restart
postmaster and run "SELECT * FROM t2". There should be one row in the
table, but it's empty.

Heikki Linnakangas wrote:
> Simon Riggs wrote:
>> On Wed, 2007-10-17 at 17:18 +0800, Jacky Leng wrote:
>>> Second, suppose that no checkpoint has occured during the upper 
>>> series--authough not quite possible; 
>> That part is irrelevant. It's forced out to disk and doesn't need
>> recovery, with or without the checkpoint.
>> There's no hole that I can see.
> No, Jacky is right. The same problem exists at least with CLUSTER, and I
> think there's other commands that rely on immediate fsync as well.
> Attached is a shell script that demonstrates the problem on CVS HEAD
> with CLUSTER. It creates two tables, T1 and T2, both with one row. Then
> T1 is dropped, and T2 is CLUSTERed, so that the new T2 relation file
> happens to get the same relfilenode that T1 had. Then we crash the
> server, forcing a WAL replay. After that, T2 is empty. Oops.
> Unfortunately I don't see any easy way to fix it. One approach would be
> to avoid reusing the relfilenodes until next checkpoint, but I don't see
> any nice place to keep track of OIDs that have been dropped since last
> checkpoint.

  Heikki Linnakangas

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