Re: Deadlock on "select ... for update"?

On 11/29/11 10:36 AM, Scott Marlowe wrote:
> On Tue, Nov 29, 2011 at 11:15 AM, Craig James
> <craig_james@emolecules.com>  wrote:
>> Several times recently one of our databases has gotten stuck with the
>> following situation:
>>
>> postgres=# select datname, procpid, usename, current_query from
>> pg_stat_activity where current_query != '<IDLE>';
>>    datname   | procpid | usename  |
>>    current_query
>>
------------+---------+----------+--------------------------------------------------------------------------------------------------------
>>   emolecules |   13503 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid<= 0 for update
>>   emolecules |   32082 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid<= 0 for update
>>   emolecules |   17974 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid<= 0 for update
>>   emolecules |   31299 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid = 0 limit 1 for update
>>   emolecules |   30247 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid = 0 limit 1 for update
>>   postgres   |    1705 | postgres | select datname, procpid, usename,
>> current_query from pg_stat_activity where current_query != '<IDLE>';
>>   emolecules |   28866 | customerdb |<IDLE>  in transaction
>>   emolecules |   21394 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid = 0 limit 1 for update
>>   emolecules |   22237 | customerdb | select tableid from hitlist_table_pool
>> where hitlistid = 0 limit 1 for update
>> (9 rows)
>>
>> It's obvious that they're all waiting ... but for what?  The "<IDLE>"
>> process looks like the culprit, but how do I figure out what it's doing?
>> The next time this happens, what queries can I run to help diagnose what's
>> going on?
>> This is PG 8.4.4 on Ubuntu 10.
> Does this help?
>
> http://wiki.postgresql.org/wiki/Lock_Monitoring

Yes, thanks! That's exactly what I needed.

Craig