Re: Practical question.

Tom Lane wrote:
> louis gonzales <gonzales(at)linuxlouis(dot)net> writes:
>> As an example:
>> insertX which initiates the trigger reads the 'nextvalue' from the
>> sequence and begins to create the associcated table
>> insertY happens almost at the same time, so that it gets the same
>> 'nextvalue' from the sequence

That won't happen because of isolation :). When InsertX increments the
sequence, it is forever incremented, so when InsertY increments it gets
the next value... e.g;

CREATE TABLE foo(id serial);

Transaction 1:
BEGIN;
INSERT INTO foo(id) VALUES (DEFAULT);
id now == 1

Transaction 2:
BEGIN;
INSERT INTO foo(id) VALUES (DEFAULT);
id now == 2

Transaction 1;
COMMIT;

Transaction 2;
COMMIT;

Even if Transaction 1 were to rollback, it has already incremented the
sequence so the next transaction would get 3.

Joshua D. Drake

>
> [ blink... ] Whatever makes you think that could happen?
>
> regards, tom lane
>
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> TIP 5: don't forget to increase your free space map settings
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