what does pg_activity mean when the database is stuck?

I have a problem where postgresql 9.3 got stuck, and the number of
postgresql processes increased from about 15 to 225 in 10 minutes.

I ran the query:
select pid, query_start, waiting, state, query from pg_stat_activity order
by query_start;

But it showed mostly select statements -- all of them the same one, with a
couple of joins. They are not in a waiting state but have been running for
over 2 hours.

I also checked for locks with the query on
http://wiki.postgresql.org/wiki/Lock_Monitoring

But it returned no locked tables.

So what does this mean? Is the select query getting stuck?
--
Si Chen
Open Source Strategies, Inc.
sichen(at)opensourcestrategies(dot)com
http://www.OpenSourceStrategies.com
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