Re: WIP Patch: Add a function that returns binary JSONB as a bytea

Stephen Frost <sfrost(at)snowman(dot)net> writes:
> * Tom Lane (tgl(at)sss(dot)pgh(dot)pa(dot)us) wrote:
>> I dunno, I do not think it's a great idea to expose jsonb's internal
>> format to the world. We intentionally did not do that when the type
>> was first defined --- that's why its binary I/O format isn't already
>> like this --- and I don't see that the tradeoffs have changed since then.

> I disagree- it's awfully expensive to go back and forth between string
> and a proper representation.

Has anyone put any effort into making jsonb_out() faster? I think that
that would be way more productive. Nobody is going to want to write
code to convert jsonb's internal form into whatever their application
uses; particularly not dealing with numeric fields.

In any case, the approach proposed in this patch seems like the worst
of all possible worlds: it's inconsistent and we get zero benefit from
having thrown away our information-hiding. If we're going to expose the
internal format, let's just change the definition of the type's binary
I/O format, thereby getting a win for purposes like COPY BINARY as well.
We'd need to ensure that jsonb_recv could tell whether it was seeing the
old or new format, but at worst that'd require prepending a header of
some sort. (In practice, I suspect we'd end up with a wire-format
definition that isn't exactly the bits-on-disk, but something easily
convertible to/from that and more easily verifiable by jsonb_recv.
Numeric subfields, for instance, ought to match the numeric wire
format, which IIRC isn't exactly the bits-on-disk either.)

regards, tom lane