Message-ID: <56ad15e3-624d-4a22-921f-82129d31bfaa@joeconway.com>
Date: Wed, 6 Dec 2023 11:15:39 -0500
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Subject: Re: Emitting JSON to file using COPY TO
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To: Andrew Dunstan <andrew@dunslane.net>, Davin Shearer <davin@apache.org>,
 PostgreSQL-development <pgsql-hackers@postgresql.org>
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From: Joe Conway <mail@joeconway.com>
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Precedence: bulk

On 12/6/23 10:32, Andrew Dunstan wrote:
> 
> On 2023-12-06 We 08:49, Joe Conway wrote:
>> On 12/6/23 07:36, Andrew Dunstan wrote:
>>>
>>> On 2023-12-05 Tu 16:46, Joe Conway wrote:
>>>> On 12/5/23 16:20, Andrew Dunstan wrote:
>>>>> On 2023-12-05 Tu 16:09, Joe Conway wrote:
>>>>>> On 12/5/23 16:02, Joe Conway wrote:
>>>>>>> On 12/5/23 15:55, Andrew Dunstan wrote:
>>>>>>>> and in any other case (e.g. LINES) I can't see why you
>>>>>>>> would have them.
>>>>>>
>>>>>> Oh I didn't address this -- I saw examples in the interwebs of 
>>>>>> MSSQL server I think [1] which had the non-array with commas 
>>>>>> import and export style. It was not that tough to support and the 
>>>>>> code as written already does it, so why not?
>>>>>
>>>>> That seems quite absurd, TBH. I know we've catered for some 
>>>>> absurdity in
>>>>> the CSV code (much of it down to me), so maybe we need to be 
>>>>> liberal in
>>>>> what we accept here too. IMNSHO, we should produce either a single 
>>>>> JSON
>>>>> document (the ARRAY case) or a series of JSON documents, one per row
>>>>> (the LINES case).
>>>>
>>>> So your preference would be to not allow the non-array-with-commas 
>>>> case but if/when we implement COPY FROM we would accept that format? 
>>>> As in Postel'a law ("be conservative in what you do, be liberal in 
>>>> what you accept from others")?
>>>
>>>
>>> Yes, I think so.
>>
>> Awesome. The attached does it that way. I also ran pgindent.
>>
>> I believe this is ready to commit unless there are further comments or 
>> objections.
> 
> Sorry to bikeshed a little more, I'm a bit late looking at this.
> 
> I suspect that most users will actually want the table as a single JSON
> document, so it should probably be the default. In any case FORCE_ARRAY
> as an option has a slightly wrong feel to it.

Sure, I can make that happen, although I figured that for the 
many-rows-scenario the single array size might be an issue for whatever 
you are importing into.

> I'm having trouble coming up with a good name for the reverse of
> that, off the top of my head.

Will think about it and propose something with the next patch revision.


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