Re: Emitting JSON to file using COPY TO

Joe Conway <mail@joeconway.com>

From: Joe Conway <mail@joeconway.com>

To: "David G. Johnston" <david.g.johnston@gmail.com>

Cc: Daniel Verite <daniel@manitou-mail.org>, Andrew Dunstan <andrew@dunslane.net>, Davin Shearer <davin@apache.org>, PostgreSQL-development <pgsql-hackers@postgresql.org>

Date: 2023-12-07T01:14:09Z

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 →

Add option force_array for COPY JSON FORMAT
- 4c0390ac53b7 19 (unreleased) landed
json format for COPY TO
- 7dadd38cda95 19 (unreleased) landed
introduce CopyFormat, refactor CopyFormatOptions
- a2145605ee3d 19 (unreleased) landed
Doc: add IDs to copy.sgml's <varlistentry> and <refsect1>
- e4018f891dec 19 (unreleased) cited

On 12/6/23 20:09, David G. Johnston wrote:
> On Wed, Dec 6, 2023 at 5:57 PM Joe Conway <mail@joeconway.com 
> <mailto:mail@joeconway.com>> wrote:
> 
>     On 12/6/23 19:39, David G. Johnston wrote:
>      > On Wed, Dec 6, 2023 at 4:45 PM Joe Conway <mail@joeconway.com
>     <mailto:mail@joeconway.com>
>      > <mailto:mail@joeconway.com <mailto:mail@joeconway.com>>> wrote:
> 
>      > But I still cannot shake the belief that using a format code of 1 -
>      > which really could be interpreted as meaning "textual csv" in
>     practice -
>      > for this JSON output is unwise and we should introduce a new integer
>      > value for the new fundamental output format.
> 
>     No, I am pretty sure you still have that wrong. The "1" means binary
>     mode
> 
> 
> Ok.  I made the same typo twice, I did mean to write 0 instead of 1.

Fair enough.

> But the point that we should introduce a 2 still stands.  The new code 
> would mean: use text output functions but that there is no inherent 
> tabular structure in the underlying contents.  Instead the copy format 
> was JSON and the output layout is dependent upon the json options in the 
> copy command and that there really shouldn't be any attempt to turn the 
> contents directly into a tabular data structure like you presently do 
> with the CSV data under format 0.  Ignore the column count and column 
> formats as they are fixed or non-existent.

I think that amounts to a protocol change, which we tend to avoid at all 
costs.

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