I have a database that we want to keep track of counts of rows.
We have triggers on the rows which increment, and decrement a count
table. In order to speed up deleting many rows we have added the following
if user != 'mocospace_cleanup'
then
update user_profile_count set buddycount=buddycount-1 where
user_profile_count.uid=OLD.userid;
end
if;
However in the logs we can see the following. I have checked to make
sure that the user really is the mocospace_cleanup user and checked
manually by logging in as the mocospace_cleanup user to make sure that
the code above does what it purports to.
ERROR: deadlock detected
DETAIL: Process 23063 waits for ExclusiveLock on tuple (20502,48) of
relation 48999028 of database 14510214; blocked by process 23110.
Process 23110 waits for ShareLock on transaction 1427023217; blocked by
process 23098.
...
CONTEXT: SQL statement "update user_profile_count set
buddycount=buddycount-1 where user_profile_count.uid= $1 "
PL/pgSQL function "user_buddy_count" line 11 at SQL statement
SQL statement "DELETE FROM ONLY "public"."user_buddies" WHERE
"buddyuserid" = $1"
Dave
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