Re: DBD::Pg async requets & pg_cancel

On 2/27/07, Jacques Caron <[email protected]> wrote:
> Hi,
>
> I would like to submit the following patch for inclusion in the next
> release of DBD::Pg:
>
> http://staff.oxado.com/~jc/patch.dbd-pg.async+cancel
>
> This pretty much trivial patch adds 5 new methods:
> $sth->pg_sendquery is equivalent to $sth->execute, but only sends the
> request, and does not wait for the results
> $sth->pg_getresult handles the results
> $dbh->pg_busy tells if $sth->getresult will block
> $dbh->pg_consume handles incoming data from the server
> $dbh->pg_cancel cancels the existing query
>
> pg_sendquery and pg_getresult are really just a split of the existing
> execute method, using PQsendQuery* calls then PQgetResult rather than
> the original PQexec* calls. The original execute function now just
> successively calls both methods (it avoids a lot of code
> duplication). Apparently the PQsenqQuery* functions have been there
> for quite a while so I believe it should work in all cases, but if
> they don't leaving the execute function untouched is always an option.
>
> I have tested a few simple scenarios, but haven't tried it in
> production yet, so I can't vouch for the validity of the code, but
> the changes are quite minimal and straightforward so I don't expect
> much complication.
>
> Any comments welcome.
>

I like the idea of natively supporting async queries.  If it's done
right, at a much higher level this could allow for things like easier
nonblocking POE<->DBI integration.  Rather than having ->pg_* custom
interfaces though, I'd really like to see someone spec up a good
generic interface for async queries for DBI itself, and then have Pg
implement them (should take a gander at a few other DBs and see what
their native async interfaces look like, to help formulate what the
generic API should look like).  Also, it would be nice if there were a
way to get async notification via a selectable filehandle or something
of that nature, instead of having to periodically check the busy
status.

-- Brandon