On Wed, Dec 6, 2023, at 3:59 PM, Daniel Verite wrote:
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?
At least the json non-ARRAY case ("json lines") doesn't have
this issue, since every CopyData message corresponds effectively
to a row in the table.
Moreover, if your interface wants to process the COPY data stream while
receiving it, you cannot provide "json array" format because each row (plus all
of the received ones) is not a valid JSON. Hence, a JSON parser cannot be
executed until you receive the whole data set. (wal2json format 1 has this
disadvantage. Format 2 was born to provide a better alternative -- each row is
a valid JSON.) I'm not saying that "json array" is not useful but that for
large data sets, it is less useful.