Re: Postgres and mod_perl: table locked during vacuum?

Jeff Boes <jboes@nexcerpt.com> writes:
> We are experiencing a fairly predictable lock-up in the overnight VACUUM
> ANALYZE maintenance script.  The VACUUM gets to the pg_class table and
> then stops, obviously waiting for something else to give up control of
> the table.  The VACUUM script resumes precisely when the web server is
> bounced.  The web server is using mod_perl, and mod_perl uses DBI code
> (in a locally developed module that does establish a connection at
> *compile* time in order to verify existence of tables used in the
> code).

I suppose you're not running 7.2 ?

Turn on debug_print_query and look at the log to see what queries
are being issued.  I'll bet lunch that the webserver code is doing
something like

    begin;
    select * from pg_class where ... ;
    <<go to sleep indefinitely>>

            regards, tom lane