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] ----------------------------------------------------------------------------------- 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. ----------------------------------------------------------------------------------- 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@xxxxxxxx
