If the reccord you are inserting do not depend on data in the record you
want to delete, why not simply use a trigger?
Before insert delete the record with the same key!
Michael Paesold wrote:
Tsirkin Evgeny wrote:
one moer question ,how did you tested it?
I have tested this here. I don't really know if this is just the case
with
Best Regards,
Michael Paesold
First I created the your schedule table. Then I opened two psql sessions...
Session A Session B
BEGIN;
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
DELETE FROM schedule WHERE studentid = 1;
INSERT INTO schedule VALUES (1, 1, 0, 0);
BEGIN;
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
DELETE FROM schedule WHERE studentid = 1;
-- if there existed records for this delete,
-- session B will now wait for session A to
-- commit/rollback and error out on commit;
-- otherwise no error
COMMIT;
INSERT INTO schedule VALUES (1, 1, 0, 0);
COMMIT;
You can also try and rollback the first transaction etc.
Again, what really helps is:
ALTER TABLE schedule ADD CONSTRAINT uniq_schedule UNIQUE (studentid,
groupid);
Best Regards,
Michael Paesold
---------------------------(end of broadcast)---------------------------
TIP 3: if posting/reading through Usenet, please send an appropriate
subscribe-nomail command to [EMAIL PROTECTED] so that your
message can get through to the mailing list cleanly
---------------------------(end of broadcast)---------------------------
TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
