| From: | Kevin Grittner <kgrittn(at)ymail(dot)com> |
|---|---|
| To: | "kop(at)meme(dot)com" <kop(at)meme(dot)com>, "pgsql-bugs(at)postgresql(dot)org" <pgsql-bugs(at)postgresql(dot)org> |
| Subject: | Re: BUG #12469: pg_locks shows locks held by pids not found i n pg_stat_activity or ps |
| Date: | 2015-01-09 18:07:35 |
| Message-ID: | 1511260135.4208486.1420826855952.JavaMail.yahoo@jws10056.mail.ne1.yahoo.com |
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| Lists: | pgsql-bugs |
"kop(at)meme(dot)com" <kop(at)meme(dot)com> wrote:
> I found that after running a large transaction (for days, it's still
> running) and then running out of shared memory that pg_locks reports locks
> held by pids that do not seem to exist, either in ps output or in
> pg_stat_activity.
That is not a bug. For details see either of the below links:
http://vldb.org/pvldb/vol5/p1850_danrkports_vldb2012.pdf
The short explanation is that SIReadLocks on a serializable
transaction may need to be kept until overlapping transactions
terminate. You can minimize this by flagging transactions which
will not modify data as READ ONLY. If a READ ONLY transaction is
expected to run for a very long time, it is wise to also flag it as
DEFERRABLE.
--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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