Re: [patch] libpq one-row-at-a-time API

Hey, this thread was pointed out to me just a few days ago, but I'll start
by saying that I think this thread is on exactly the right track. I don't
like the callback API, and think that PQsetSingleRowMode should be offered
in place of it. But I do have one

On Sat, Jun 16, 2012 at 10:22 AM, Marko Kreen <markokr(at)gmail(dot)com> wrote:
>
> The function can be called only after PQsend* and before any
> rows have arrived. This guarantees there will be no surprises
> to PQexec* users who expect full resultset at once.

Ok, I'm guessing you mean that "before you call PQgetResult or
PQgetRowData", or maybe "before you call PQgetResult or PQgetRowData and
it returns a result or partial result." Because it would be a race
condition if you meant exactly what you said. (Though I don't understand
how this could possibly be implemented without some source of concurrency,
which libpq doesn't do.) Maybe this is a little overly pendantic, but I
do want to confirm the intention here.

One other possibility, Tom Lane fretted ever so slightly about the use of
malloc/free per row... what about instead of PQsetSingleRowMode, you have
PQsetChunkedRowMode that takes a chunkSize parameter. A chunkSize <= 0
would be equivalent to what we have today, a chunkSize of 1 means you get
what you have from PQsetSingleRowMode, and larger chunkSizes would wait
until n rows have been received before returning them all in a single
result. I don't know that this suggestion is all that important, but
it seems like an obvious generalization that might possibly be useful.

Best,
Leon