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<p class=MsoNormal>We suffered a deadlock at one point today and I’m
looking for some advice on how to prevent it from happening again. In the
postgres log I found the following:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>ERROR: deadlock detected<o:p></o:p></p>
<p class=MsoNormal>DETAIL: Process 20230 waits for ExclusiveLock on
relation 31152 of database 26523; blocked by process 27297.<o:p></o:p></p>
<p class=MsoNormal> Process 27297
waits for AccessExclusiveLock on relation 31205 of database 26523; blocked by
process 20230.<o:p></o:p></p>
<p class=MsoNormal> Process 20230:
select "_payments_cluster".ddlScript_prepare(1, -1);<o:p></o:p></p>
<p class=MsoNormal> Process 27297:
select "_payments_cluster".cleanupEvent('10 minutes'::interval,
'false'::boolean);<o:p></o:p></p>
<p class=MsoNormal>HINT: See server log for query details.<o:p></o:p></p>
<p class=MsoNormal>CONTEXT: SQL statement "LOCK TABLE
_payments_cluster.sl_event IN EXCLUSIVE MODE; INSERT INTO
_payments_cluster.sl_event (ev_origin, ev_seqno, ev_timestamp, ev_snapshot,
ev_type, ev_data1, ev_data2, ev_data3, ev_data4, ev_data5, ev_data6, ev_data7,
ev_data8) VALUES ('1', nextval('_payments_cluster.sl_event_seq'), now(),
"pg_catalog".txid_current_snapshot(), $1, $2, $3, $4, $5, $6, $7, $8,
$9); SELECT currval('_payments_cluster.sl_event_seq');"<o:p></o:p></p>
<p class=MsoNormal> SQL statement
"SELECT
"_payments_cluster".createEvent('_payments_cluster', 'SYNC',
NULL)"<o:p></o:p></p>
<p class=MsoNormal> PL/pgSQL function
"ddlscript_prepare" line 29 at PERFORM<o:p></o:p></p>
<p class=MsoNormal>STATEMENT: select
"_payments_cluster".ddlScript_prepare(1, -1);<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>So it looks to me like the issue was caused by a ddl script
running at the same time as a slony cleanupEvent command. Our system requires
some dynamic changes to our db structure (in the form of new partitions and
things like that) these ddl scripts could run at any time. So, how can I best
manage this around the cleanupEvents?<o:p></o:p></p>
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