Re: WAL-files restore and nextval('PK')

Andreas Gaab <A(dot)Gaab(at)scanlab(dot)de> writes:
> after an WAL-restore of our Postgres DB, we observe seemingly wrong values of our sequences.

> We have two postgres server (8.4) with pgpool in replication mode.

> Recently we tested our restore procedure and played our WAL-files into the second server after an old file-system backup was restored.
> Accidently, we aborted the starting server and had to restart it and therefore started WAL-replay again.

> Now we observe, that the newly restored server has higher values in his sequences as the other server.

It's normal for sequence counters to be a few counts higher after a
crash-and-restart than they would have been if no crash had occurred.
This is an intentional design tradeoff to minimize the WAL overhead
associated with assigning a sequence value. If you find it intolerable
for what you're doing, I believe you can prevent it by adjusting the
sequence parameters to prevent any "caching" of values.

regards, tom lane