Re: non-blocking connections in libpq, fix proposal

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Bernhard Herzog wrote:
> 
> Hi,
> 
> after finding out that libpq apparently doesn't work properly when
> sending long queries ('long' meaning somewhere larger than 8KB), I had a
> look at the sources and also found some mails in the archives where this
> issue had been discussed. The problem appears to be still present in the
> current CVS version.
> 
> I've worked on a fix today that works for me. It's perhaps not the best
> solution but it's simple :-)
> 
> The basic strategy is to fix pqFlush and pqPutBytes.
> 
> The problem with pqFlush as it stands now is that it returns EOF when an
> error occurs or when not all data could be sent. The latter case is
> clearly not an error for a non-blocking connection but the caller can't
> distringuish it from an error very well.
> 
> The first part of the fix is therefore to fix pqFlush. This is done by
> to renaming it to pqFlushSome which only differs from pqFlush in its
> return values to allow the caller to make the above distinction and a
> new pqFlush which is implemented in terms of pqFlushSome and behaves
> exactly like the old pqFlush.
> 
> The second part of the fix modifies pqPutBytes to use pqFlushSome
> instead of pqFlush and to either send all the data or if not all data
> can be sent on a non-blocking connection to at least put all data into
> the output buffer, enlarging it if necessary.
> 
> I've also added a new API function PQflushSome which analogously to
> PQflush just calls pqFlushSome. Programs using PQsendQuery should use
> this new function. The main difference is that this function will have
> to be called repeatedly (calling select() properly in between) until all
> data has been written.
> 
> 
> Being new to postgresql development I'm not completely sure how to
> proceed from here. Is it OK if I post the patch here?
> 
> 
>    Bernhard
> 
> 
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