On Mon, Feb 10, 2014 at 5:38 PM, Andres Freund <and...@2ndquadrant.com> wrote:
> On 2014-02-10 17:35:12 -0600, Merlin Moncure wrote:
>> Wrong.  You still need to have code that checks the server version and
>> see if it's supported (particularly for sending) and as there is *no
>> protocol negotiation of the formats at present it's all going to boil
>> down to if version = X do Y*.   How does the server know which
>> 'versions' are ok to send? It doesn't.  Follow along with me here:
>> Suppose we don't introduce a version flag today and change the format
>> to some more exotic structure for 9.5.  How has the version flag made
>> things easier for the client?  It hasn't. The client goes "if version
>> = X do Y".
> think of binary COPY outputting data in 9.4 and then trying to import
> that data into 9.5. That's the interesting case here.

right, json could be made work, but any other format change introduced
to any other already existing type will break.  That's not a real
solution unless we decree henceforth that no formats will change from
here on in, in which case I withdraw my objection.

I think COPY binary has exactly the same set of considerations as the
client side.  If you want to operate cleanly between versions (which
has never been promised in the past), you have to encode in a header
the kinds of things the server would need to parse it properly.
Starting with, but not necessarily limited to, the encoding server's


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