Re: Binary support for pgoutput plugin

Hi,

On 2019-06-07 20:52:38 -0400, Chapman Flack wrote:
> It seems they had ended up designing a whole 'nother "protocol level"
> involving queries wrapping their results as JSON and an app layer that
> unwraps again, after trying a simpler first approach that was foiled by the
> inability to see into arrays and anonymous record types in the 'describe'
> response.

I suspect quite a few people would have to have left the projectbefore
this would happen.

> I thought, in a new protocol rev, why not let the driver send additional
> 'describe' messages after the first one, to drill into structure of
> individual columns mentioned in the first response, before sending the
> 'execute' message?
>
> If it doesn't want the further detail, it doesn't have to ask.
>
> > And then we suddenly need tracking for all these, so we don't always
> > send out that information when we previously already did
>
> If it's up to the client driver, it can track what it needs or already has.

> I haven't looked too deeply into the replication protocol ... it happens
> under a kind of copy-both, right?, so maybe there's a way for the receiver
> to send some inquiries back, but maybe in a windowed, full-duplex way where
> it might have to buffer some incoming messages before getting the response
> to an inquiry message it sent.

That'd be a *lot* of additional complexity, and pretty much prohibitive
from a performance POV. We'd have to not continue decoding on the server
side *all* the time to give the client a chance to inquire additional
information.

Greetings,

Andres Freund