Thread

Re: libpq: PQgetCopyData() and allocation overhead

Jeroen Vermeulen <jtvjtv@gmail.com> — 2023-02-10T10:32:00Z

Here's the patch (as a PR just to make it easy to read):
https://github.com/jtv/postgres/pull/1

I don't have an easily readable benchmark yet, since I've been timing the
potential impact on libpqxx.  But can do that next.


Jeroen

On Fri, Feb 10, 2023, 11:26 Bharath Rupireddy <
bharath.rupireddyforpostgres@gmail.com> wrote:

> On Fri, Feb 10, 2023 at 3:43 PM Jeroen Vermeulen <jtvjtv@gmail.com> wrote:
> >
> > Would there be interest in a variant of PQgetCopyData() that re-uses the
> same buffer for a new row, rather than allocating a new buffer on each
> iteration?
> >
> > I tried it on a toy benchmark, and it reduced client-side CPU time by
> about 12%.  (Less of a difference in wall-clock time of course; the client
> was only using the CPU for a bit over half the time.)
>
> Interesting. It might improve logical replication performance too as
> it uses COPY protocol.
>
> Do you mind sharing a patch, test case that you used and steps to
> verify the benefit?
>
> --
> Bharath Rupireddy
> PostgreSQL Contributors Team
> RDS Open Source Databases
> Amazon Web Services: https://aws.amazon.com
>