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From: Joe Conway <[email protected]>
To: Daniel Verite <[email protected]>
To: Andrew Dunstan <[email protected]>
Cc: Davin Shearer <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Subject: Re: Emitting JSON to file using COPY TO
Date: Wed, 6 Dec 2023 14:47:25 -0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

On 12/6/23 13:59, Daniel Verite wrote:
> 	Andrew Dunstan wrote:
> 
>> IMNSHO, we should produce either a single JSON 
>> document (the ARRAY case) or a series of JSON documents, one per row 
>> (the LINES case).
> 
> "COPY Operations" in the doc says:
> 
> " The backend sends a CopyOutResponse message to the frontend, followed
>     by zero or more CopyData messages (always one per row), followed by
>     CopyDone".
> 
> In the ARRAY case, the first messages with the copyjsontest
> regression test look like this (tshark output):
> 
> PostgreSQL
>      Type: CopyOut response
>      Length: 13
>      Format: Text (0)
>      Columns: 3
> 	Format: Text (0)
> PostgreSQL
>      Type: Copy data
>      Length: 6
>      Copy data: 5b0a
> PostgreSQL
>      Type: Copy data
>      Length: 76
>      Copy data:
> 207b226964223a312c226631223a226c696e652077697468205c2220696e2069743a2031…
> 
> The first Copy data message with contents "5b0a" does not qualify
> as a row of data with 3 columns as advertised in the CopyOut
> message. Isn't that a problem?


Is it a real problem, or just a bit of documentation change that I missed?

Anything receiving this and looking for a json array should know how to 
assemble the data correctly despite the extra CopyData messages.

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

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