John Siracusa wrote:
> On 6/7/07 3:04 AM, Cees Hek wrote:
>> On 6/7/07, Neal Clark <[EMAIL PROTECTED]> wrote:
>>> Also, I do not understand why Rose::DB goes to the trouble of getting
>>> tangled
>>> up in the serial sequence when a value 'DEFAULT' for the id to the statement
>>> handler would do the same thing.
>> Usually this is done so that the code knows exactly what the primary
>> key for the row is going to be. If you just insert using DEFAULT,
>> then you usually have to make an extra call to the DB to retrieve the
>> record again to find out what id was assigned to the row
>
> Right, that's why RDBO pre-allocates the serial value. I believe the Pg
> call to "get me the last value pulled from this sequence in this session" is
> also a safe way to do it, but I'm not 100% sure. Pre-allocating is 100%
> safe in that, if the insert succeeds, I know for sure what value it used,
> with no worries about race conditions.
And not to appeal to authority, but Tom Lane suggests this same approach:
>This is the Right Way To Do It. You do not need the transaction
>(because currval() is backend-private anyway). I'd not bother with
>currval() at all, but just do
>
> SELECT nextval('some_table_id_sequence');
>
> -- this returns 4242, say
>
> INSERT INTO some_table(id, name, surname)
> VALUES(4242, 'marc', 'moua');
>
>Simple, reliable, fast.
>
> regards, tom lane
Maurice
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