Re: SendRowDescriptionMessage() is slow for queries with a lot of columns

Hi,

On 2017-10-11 18:05:32 +0200, Alvaro Herrera wrote:
> Well, my concern is to ensure that extension authors take advantage of
> the optimized implementation. If we never let them know that we've
> rewritten things, most are not going to realize they can make their
> extensions faster with a very simple code change.

The inline pq_gsendint() already results in faster code in a good
number of cases, as a decent compiler will often be able to evaluate at
plan time.

> On the other hand, I suppose that for the vast majority of extensions,
> doing the change is unlikely to have a noticeable in performance, so
> perhaps we should just keep the shim and move along.

Yea, I think it's unlikely to be noticeable unless you do a lot of them
in a row. Unfortunately all send functions essentially allocate a new
StringInfo - which is going to dominate execution cost. We literally
allocate 1kb to send a single four byte integer.

Fixing the output function performance requires a fairly different type
of patch imo.

> If do nothing, it's unlikely we'd ever get rid of the compat function.

I think that's ok.

Greetings,

Andres Freund