Horton

Re: Emitting JSON to file using COPY TO

Joe Conway <mail@joeconway.com>

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From: Joe Conway <mail@joeconway.com>
To: Nathan Bossart <nathandbossart@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andrew Dunstan <andrew@dunslane.net>, Davin Shearer <davin@apache.org>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2023-12-07T12:15:28Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add option force_array for COPY JSON FORMAT

  2. json format for COPY TO

  3. introduce CopyFormat, refactor CopyFormatOptions

  4. Doc: add IDs to copy.sgml's <varlistentry> and <refsect1>

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