Re: Emitting JSON to file using COPY TO

On 12/6/23 21:56, Nathan Bossart wrote:
> On Wed, Dec 06, 2023 at 03:20:46PM -0500, Tom Lane wrote:
>> If Nathan's perf results hold up elsewhere, it seems like some
>> micro-optimization around the text-pushing (appendStringInfoString)
>> might be more useful than caching. The 7% spent in cache lookups
>> could be worth going after later, but it's not the top of the list.
>
> Hah, it turns out my benchmark of 110M integers really stresses the
> JSONTYPE_NUMERIC path in datum_to_json_internal(). That particular path
> calls strlen() twice: once for IsValidJsonNumber(), and once in
> appendStringInfoString(). If I save the result from IsValidJsonNumber()
> and give it to appendBinaryStringInfo() instead, the COPY goes ~8% faster.
> It's probably worth giving datum_to_json_internal() a closer look in a new
> thread.

Yep, after looking through that code I was going to make the point that
your 11 integer test was over indexing on that one type. I am sure there
are other micro-optimizations to be made here, but I also think that it
is outside the scope of the COPY TO JSON patch.

--
Joe Conway
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com