Re: Emitting JSON to file using COPY TO

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