On 08/19/2014 07:10 PM, Alvaro Herrera wrote:
Stephen Frost wrote:
* Heikki Linnakangas (hlinnakan...@vmware.com) wrote:

Indeed, the ODBC driver only uses libpq for authentication, then
calls PQgetssl(), and takes over the whole show calling SSL_read()
and SSL_write() itself. Ideally, we'd modify psqlodbc to stop doing
that, but that's not an easy job. In the short-term, I think we need
to export pqsecure_read() and pqsecure_write() functions in libpq,
so that the ODBC driver can use those instead of SSL_read() and

Yeah, that's what I remembered.  There was an attempt to make that
change at one point, but it was reverted due to the lack of batching
ability in libpq (without resorting to cursors, as I recall...),
requiring double the memory usage.  Still, if pqsecure_read and
pqsecure_write are sufficient to make the ODBC driver work, that's good
news.  I had been worried it did other things with the OpenSSL struct
beyond just using those.

Um, libpq has recently gained the ability to return result fragments,
right?  Those didn't exist when libpq-ification of odbc was attempted,
as I recall -- perhaps it's possible now.

IIRC the thing that psqlodbc does that libpq doesn't support is sending multiple queries to the backend, and then wait for *all* the replies to arrive, in a single round-trip. The closest thing is using PQexec("foo; bar;"), but that's quite limited.

- Heikki

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