From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Tobias Brox <tobixen(at)gmail(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: locking issue on simple selects? |
Date: | 2010-09-15 13:39:47 |
Message-ID: | 4096.1284557987@sss.pgh.pa.us |
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Lists: | pgsql-performance |
Tobias Brox <tobixen(at)gmail(dot)com> writes:
> Recently we've frequently encountered issues where some simple selects
> (meaning, selects doing an index lookup and fetching one row) have
> become stuck for several minutes. Apparently all requests on one
> exact table gets stuck, all requests not related to said table are
> going through without any problems. According to the pg_stat_activity
> view, all queries getting stuck was read-queries (selects), no updates
> or anything like that (some of the transactions were doing updates
> and/or inserts though).
> The obvious thought seems to be that this is a locking issue ... but
> it doesn't seem so. For one thing, AFAIK locking shouldn't affect
> selects, only updates?
An exclusive lock will block selects too. Have you looked into pg_locks
for ungranted lock requests?
regards, tom lane
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