Re: PostgreSQL 7.4.10 hanging on delete

When the delete statements hangs, look into the pg_locks table, to
check if the delete statement is waiting because it has conflict with
rows locked by other transactions.

On 20 Dec 2005 16:21:53 +0000, Jonathan Parkin
<jonathan.parkin@legendplc.com> wrote:
> I have a reasonably large, live, system-critical database.  A perl
> script on another machine connects and issues a sequence of commands in
> a transaction, the last of which is a delete.  The delete never returns
> a response, and the connection never times out.  The postgres process
> handling the delete is in a scheduled state, but stracing it produces no
> output at all.
>
> The table contains entries for a "parent" and it's "children".
> Grandchildren and other descendents never exist in the table.  A before
> delete trigger removes the children when the parent is deleted and the
> delete is always issued for a parent.  Children have exactly one parent.
>
> By tcpdumping the SQL connection the system consistently hangs on the
> same delete for one of a set of rows. As the delete never commits the
> transaction is never finished.   Other rows (parents and children) can
> be deleted without issue.
>
> Killing the perl process at the other end, and subsequently the
> connection timing out on the perl-server end does not stop the postgres
> process handling the delete, and it continues to produce no output when
> straced.
>
> Restarting the server, doing a VACUUM FULL ANALYZE and a REINDEX of all
> tables in the database (including system tables) has no effect.
>
> This was first noticed using PostgreSQL 7.4.7.  Upgrading to 7.4.10 has
> not helped. Upgrading to 8.x may not be an option due to the systems
> connecting to the database (this is being investigated).
>
> My next logical step is to stop access to the database, take a dump of
> it, remove it, and rebuild it.  Can anyone think of a reason why I
> should not do this?
>
> Can anyone think of anything else I should try?
>
> I welcome all suggestions, no matter how obvious they may appear.
>
> Thanks,
>
> Jonathan
>
> --
> Best Regards
>
> Jonathan Parkin
> Developer
>
> Legend Communications plc
> T: 0844 390 2049
> F: 0844 390 2001
> E: jonathan.parkin@legendplc.com
> W: http://www.legend.co.uk/
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--
Regards
Pandu