"Markus Hoenicka" <[EMAIL PROTECTED]> writes on
Sat, 27 May 2006 22:46:22 +0200 (METDST):
> Martin Kutschker writes:
> > Have the systems which use sequences some nameing schemes, which
> > build the sequence name from the table name?
> >
>
> SQLite and MySQL don't use sequences, so I can speak only of
> PostgreSQL (don't know about Oracle, Sybase et al.). If you use the
> Serial type in PostgreSQL, a sequence is automatically created with a
> predictable name (tablename_colname_seq). However, you can do this
> just as well:
>
> CREATE SEQUENCE whatever_seq;
> CREATE TABLE tablename (
> colname integer DEFAULT nextval('whatever_seq') NOT NULL
>
> A mechanism that relies on a particular naming scheme of sequences
> would fail in the second case.
I was aware of that. I shoud have written that the new function would only work
with the default sequence names. But this is no real problem as you can use
dbi_conn_sequence_last() if you have custom sequence names.
But now you *have* to use custom names to have predictable names for your
application.
> > And perhaps dbi couild handle the problem that Mysql doesn't store
> > the id by table or sequence but by connection by automatically
> > calling mysql_last_insert_id() on every insert and storing the ids
> > in a dbi datastructure per table.
>
> I don't see a real problem here. If an application makes sure to
> store
> relevant id values after INSERT commands, you'll get a portable code
> without causing dbi to interfere with tables behind the users back.
Yes. But the docs must, if they don't do already, state that
dbi_conn_sequence_last() must be the very first statement after an INSERT. Ok,
I think it's enough if you issue it before another INSERT, but better be strict
that get a wrong id.
I just thought it might be a bit more convenient for folks that switch to Mysql.
Masi
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