Hello Hans-Jьrgen,
Sunday, February 1, 2004, 6:41:56 PM, you wrote:
HJS> If I understand you question correctly you have to use a SERIALIZABLE
HJS> transaction to make sure that you can see the same snapshot during your
HJS> transaction.
My problem is same as:
[quote from: http://www.postgresql.org/docs/7.2/interactive/xact-serializable.html]
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I don't think serializable transactions quite give you this.
Consider the following transaction:
BEGIN
SELECT count(*) FROM bottles WHERE wall = 3; [*]
[if count < 10]
INSERT INTO bottles (wall, colour) VALUES (3, 'green');
[end if]
END
If this were run several times sequentially, it could never increase the number of
bottles on wall 3 so that there were more than 10. But if it ran several times
simultaneously, even with serializable transaction isolation, it could do so.
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Which methods are fix this trouble? Desirable not slow methods...
Very important detail:
SELECT query, marked by [*] is executed only from one function, for
example from
function bottle_add() {
BEGIN
SELECT count(*) FROM bottles WHERE wall = 3; [*]
[if count < 10]
INSERT INTO bottles (wall, colour) VALUES (3, 'green');
[end if]
END
}
but in all other (many many) functions exists selects from 'battles'
table too, and locking _all_ rows in table 'battles' for read/write
are disagree. May be i need to do locking not row's, but queries?
Locking on application layer? Help plz.
Sorry for bad english ;(
--
Best regards,
Alexander mailto:voodoo@wenet.ru
