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: Andrew Dunstan <andrew@dunslane.net>, Davin Shearer <davin@apache.org>, PostgreSQL-development <pgsql-hackers@postgreSQL.org>
Date: 2023-12-03T19:24:53Z
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 12/3/23 11:03, Joe Conway wrote:
> On 12/3/23 10:10, Andrew Dunstan wrote:
>> I  realize this is just a POC, but I'd prefer to see composite_to_json()
>> not exposed. You could use the already public datum_to_json() instead,
>> passing JSONTYPE_COMPOSITE and F_RECORD_OUT as the second and third
>> arguments.
> 
> Ok, thanks, will do

Just FYI, this change does loose some performance in my not massively 
scientific A/B/A test:

8<---------------------------
-- with datum_to_json()
test=# \timing
Timing is on.
test=# copy foo to '/tmp/buf' (format json, force_array);
COPY 10000000
Time: 37196.898 ms (00:37.197)
Time: 37408.161 ms (00:37.408)
Time: 38393.309 ms (00:38.393)
Time: 36855.438 ms (00:36.855)
Time: 37806.280 ms (00:37.806)

Avg = 37532

-- original patch
test=# \timing
Timing is on.
test=# copy foo to '/tmp/buf' (format json, force_array);
COPY 10000000
Time: 37426.207 ms (00:37.426)
Time: 36068.187 ms (00:36.068)
Time: 38285.252 ms (00:38.285)
Time: 36971.042 ms (00:36.971)
Time: 35690.822 ms (00:35.691)

Avg = 36888

-- with datum_to_json()
test=# \timing
Timing is on.
test=# copy foo to '/tmp/buf' (format json, force_array);
COPY 10000000
Time: 39083.467 ms (00:39.083)
Time: 37249.326 ms (00:37.249)
Time: 38529.721 ms (00:38.530)
Time: 38704.920 ms (00:38.705)
Time: 39001.326 ms (00:39.001)

Avg = 38513
8<---------------------------

That is somewhere in the 3% range.

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