The use case is something like:-
·There is a table let’s say “A” and the trigger is created on this table
let say “A_TRIGGER”.
·The trigger captures the data change happens in table A into table B.
·There would be a huge insert, update, delete on table A, the side
effect of it table B also get updated very frequently.
In my recent observation I seen deadlocks with ShareLock, when any trigger doing with INSERT/UPDATE/DELETE.
As Robins Tharakan said its also with any blocking operation like REINDEX.
If your logs looking like
Eg:-
2011-07-09 04:10:44 ETC/GMT ERROR: deadlock detected2011-07-09 04:10:44 ETC/GMT DETAIL: Process 22986 waits for ShareLock on transaction 939; blocked by process 22959.
Then I say, you need to give a try by testing Lock on Parent Table (i.e. in your case A) by SHARE UPDATE EXCLUSIVE MODE in trigger calling function.
Eg:-
CREATE OR REPLACE FUNCTION CHILD_TEST() RETURNS TRIGGER
AS
$$
BEGIN
LOCK TABLE PARENT IN SHARE UPDATE EXCLUSIVE MODE;
UPDATE PARENT SET A=NEW.A;
RETURN NEW;
END;
$$
LANGUAGE PLPGSQL;
Here SHARE UPDATE EXCLUSIVE MODE Works as a Select For update clause.
I believe you should give a try test on this.
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Regards,
Raghavendra
EnterpriseDB Corporation