Re: improving async support in psycopg

On Sun, Mar 28, 2010 at 2:35 AM, Daniele Varrazzo
<[email protected]> wrote:
> On Sat, Mar 27, 2010 at 2:40 AM, Jan Urbański <[email protected]> wrote:
>
>> Skimming over the patches I have a question: is it really necessary to add
>> the callback feature into the C library? AFAICS the callback is executed on
>> asynchronous cursors everytime there is a execute() attempt. Couldn't you
>> just write a Python psycopg2.extensions.cursor subclass that overrides
>> execute() by calling that callback?
>
> As things are now, execute and callproc being the only methods using
> async features, this is the case. Probably it will be too extending
> support to other currently blocking methods (begin/commit/rollback
> etc).
>
> Yes, it is probably the case to think about Python subclasses to add a
> wait wrapper around async methods. the psycopg.extras module could
> provide such wrappers exposing a method, equivalent to the callback in
> my test, to be customized by async libraries to fit their framework.

OTOH, looking at the pqpath.c, many functions call PQexec (via
pq_execute_command_locked) and set the connection state according to
its result (begin, commit and rollback). reset() instead executes a
sequence of 2 or 3 operations (something similar to what connect()
does). If those methods were to be made async, it seems to me that the
knowledge about "how to block" should be available at C level.

-- Daniele
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