Hi All!
I use postgresql and I have to emulate partial sequence (sequence with
predicate).
I have transactions table with "serial_id" field - this field have to
be autoincrement field and unique for "commit_date" and
"user_office_id".
When I perform an insert to this table I have to do something like
that in SQL:
BEGIN;
LOCK transactions IN ROW SHARE MODE;
SELECT serial_id FROM transactions WHERE FOR UPDATE;
MAX_SERIAL_ID = SELECT MAX(serial_id) FROM transactions WHERE
commit_date=CURRENT_TIMESTAMP AND user_office_id=93;
INSERT INTO transactions VALUES (MAX_SERIAL_ID+1, 93, 'other data1'),
(MAX_SERIAL_ID+1, 93, 'other data2'), (MAX_SERIAL_ID+1, 93, 'other
data3');
COMMIT;
--OR--
last_serial = execute(select([func.max(transactions.c.serial)],
transactions.c.user_office_id==93,
transactions.c.commit_date==datetime.date.today())).fetchone()[0]
AND then execute(transactions_table.insert(), [{93, last_serial+1,
'other', 'data'}, ...])
How to do that to not allow other insert's to be executed between my
select and insert statements from other requests and I don't want to
block select statements to transactions table!? Is there any "magic"
in SA to do that or may be I choose wrong way to do that kind of
stuff? Help me please I'm stucked with that :(
Thanks a lot!
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