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    <p>Check the <code>pg_stat_activity</code> view, there is probably some other transaction blocking the schema change.</p> <pre><code>select * from pg_stat_activity where not waiting and xact_start is not NULL order by xact_start; </code></pre> <p>The first row to show up is probably the one causing problems. It is often an "idle in transaction" - this may very well hold locks, and if it's an old transaction it may as well kill performance. Probably the programmer forgot to ensure ending the transaction with "commit" or "rollback", or maybe some db session got stuck due to network problems.</p> <p>To terminate transaction with pid 1234, use <code>select pg_cancel_backend(1234);</code> or (from the shell) <code>kill 1234</code>. If that fails, see <a href="https://serverfault.com/questions/35332/what-do-i-do-when-pg-cancel-backend-doesnt-work">https://serverfault.com/questions/35332/what-do-i-do-when-pg-cancel-backend-doesnt-work</a></p> <p>There is also a view <code>pg_locks</code> which may give some insight, though it may probably not be that easy to get any useful info out from it. If <code>granted</code> is true, the lock is held, when <code>granted</code> is false it means the query is waiting for the lock. Here are some more hints here on how to extract useful info from pg_locks: <a href="http://wiki.postgresql.org/wiki/Lock_Monitoring" rel="nofollow noreferrer">http://wiki.postgresql.org/wiki/Lock_Monitoring</a> </p> <p>If everything else fails, restarting postgres should clear all the locks (as well as long-running transactions).</p>
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    1. COI found the query which was just hanging on `ALTER TABLE "about_contactmessage" ADD CONSTRAINT "user_id_refs_id_2a9a546ebb1d6a8b" FOREIGN KEY ("user_id") REFERENCES "auth_user" ("id") DEFERRABLE INITIALLY DEFERRED;`, I killed it with `select pg_cancel_backend(30969);` and ran the create table command again but it's still just hanging. The ALTER TABLE statement was the only one running on the DB at the time.
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    2. COI just had a look at `pg_locks`, it's full of integers. I'm going to restart postgres and try to create the table again.
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    3. COa combination of killing the hung process, restarting postgres and then trying again fixed it. Thank you very much!
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