Re: An example needed for Serializable conflict...

Durumdara wrote:
> Please send me an example (pseudo-code) for Serializable conflict.
> And I wanna know, if possible, that if more transactions only
> read the tables in Serializable mode, and one or others write
> to it, can I got some conflicts in read operation?

You get a serialization conflict if you try to modify a row
in a serializable transaction T1 that has been changed by a second
transaction T2 after T1 started.

Sample 1:

T1: START TRANSACTION ISOLATION LEVEL SERIALIZABLE;

T1: SELECT * FROM t;
id | val
----+------
1 | test
(1 row)

T2: DELETE FROM t WHERE id=1;

T1: UPDATE t SET val='new' WHERE id=1;
ERROR: could not serialize access due to concurrent update

Sample 2:

T1: START TRANSACTION ISOLATION LEVEL SERIALIZABLE;

T1: SELECT * FROM t;
id | val
----+------
1 | test
(1 row)

T2: UPDATE t SET val=val WHERE id=1;

T1: DELETE FROM t;
ERROR: could not serialize access due to concurrent update

Yours,
Laurenz Albe