Re: PATCH: Batch/pipelining support for libpq

Vaishnavi Prabakaran wrote:

> Am going to include the test which you shared in the test patch. Please let
> me know if you want to cover anymore specific cases to gain confidence.

One bit of functionality that does not work in batch mode and is left
as is by the patch is the PQfn() fast path interface and the large object
functions that use it.

Currently, calling lo_* functions inside a batch will fail with a message
that depends on whether the internal lo_initialize() has been successfully
called before.

If it hasn't, PQerrorMessage() will be:
"Synchronous command execution functions are not allowed in batch mode"
which is fine, but it comes by happenstance from lo_initialize()
calling PQexec() to fetch the function OIDs from pg_catalog.pg_proc.

OTOH, if lo_initialize() has succeeded before, a call to a large
object function will fail with a different message:
"connection in wrong state"
which is emitted by PQfn() based on conn->asyncStatus != PGASYNC_IDLE

Having an unified error message would be more user friendly.

Concerning the doc, when saying in 33.5.2:
"In batch mode only asynchronous operations are permitted"
the server-side functions are indeed ruled out, since PQfn() is
synchronous, but maybe we should be a bit more explicit
about that?

Chapter 34.3 (Large Objects / Client Interfaces) could also
mention the incompatibility with batch mode.

Best regards,
--
Daniel Vérité
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