Re: lastval()

Abhijit Menon-Sen wrote:
> At 2005-05-11 10:55:37 +1000, neilc(at)samurai(dot)com wrote:
> >
> > > Here is a small patch that implements a function lastval() [...]
> >
> > What do people think of this idea? (Tom seems opposed, I'm just
> > wondering if there are other opinions out there.)
>
> For what it's worth, I think it's a bad idea.
>
> In the MySQL wire protocol (hi Dennis!), the "last insert id" is sent
> along with every "OK" message, and the client can just keep the value
> in memory. Users call a function to retrieve that value, rather than
> issuing a "SELECT nextval()".
>
> So the server-side lastval() function is not enough for any meaningful
> compatibility. The client would also need to be changed to provide the
> pgsql_last_insert_id() or a similar function (which could do a "SELECT
> lastval()" internally).
>
> In this situation -- where both client changes AND a server round-trip
> are required -- what's the point of adding cruft to the server? Might
> as well confine changes to the client, and use nextval to implement
> the feature.
>
> By the way, what would lastval() do if an insert trigger inserts a row
> into a table with another serial column?

It fails, just like it would fail now if the trigger inserted into the
same table that used the trigger, or a rule.

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