Re: vacuum won't even start

Tom Lane a écrit :
> Jean-Christophe Praud <jc(at)steek(dot)com> writes:
>
>> I've a problem on a heavy loaded database: vacuums don't work since
>> about a week. All I got is:
>>
>
>
>> mybase=# vacuum verbose analyze public.mytable;
>> INFO: vacuuming "public.mytable"
>> (I stop it after hours)
>>
>
>
>> Looking with top and iotop, I see the process takes some cpu and disk io
>> time during several minutes, then it seems to fall asleep.
>> The process isn't locked according to pg_stat_activity.
>>
>
> When vacuum wants to clean up a particular table page, it will wait
> until no other process is examining that page; and this wait is not
> visible in pg_locks. Perhaps you have got some queries referencing
> those tables that have stopped midway and are just sitting?
>
> Although pg_locks won't immediately show the wait, it could be useful
> to help identify the culprit --- look for other processes holding
> any type of lock on the table the vacuum is stuck on, and then go to
> pg_stat_activity to see how old their current query is.
>
> regards, tom lane
>
Indeed, the tables I tried to vacuum have locks on them.
AccessShareLock belonging to queries which seem sleeping. I tried to
kill these queries but pg_cancel_backend() has no effect, and the
process doesn't get the 15 signal.

How can I get rid of these blocking queries without restarting the
server ? They are not listed as "waiting" in pg_stat_activity.

These queries are MOVE FORWARD on cursors, the underlying query is a
rather complex one (unions, joins, functions calls)

Regards,

--
JC
Ph'nglui mglw'nafh Cthulhu n'gah Bill R'lyeh Wgah'nagl fhtagn!