Re: Binary support for pgoutput plugin

On Tue, Jun 04, 2019 at 04:55:33PM -0400, Dave Cramer wrote:
> On Tue, 4 Jun 2019 at 16:46, Andres Freund <andres(at)anarazel(dot)de> wrote:
>
> > Hi,
> >
> > On 2019-06-04 16:39:32 -0400, Dave Cramer wrote:
> > > On Tue, 4 Jun 2019 at 16:30, Andres Freund <
> > andres(dot)freund(at)enterprisedb(dot)com>
> > > wrote:
> > > > > There's also no reason that I am aware that binary outputs can't be
> > > > > supported.
> > > >
> > > > Well, it *does* increase version dependencies, and does make
> > replication
> > > > more complicated, because type oids etc cannot be relied to be the same
> > > > on source and target side.
> > > >
> > > I was about to agree with this but if the type oids change from source
> > > to target you still can't decode the text version properly. Unless I
> > > mis-understand something here ?
> >
> > The text format doesn't care about oids. I don't see how it'd be a
> > problem? Note that some people *intentionally* use different types from
> > source to target system when logically replicating. So you can't rely on
> > the target table's types under any circumstance.
> >
> > I think you really have to use the textual type which we already write
> > out (cf logicalrep_write_typ()) to call the binary input functions. And
> > you can send only data as binary that's from builtin types - otherwise
> > there's no guarantee at all that the target system has something
> > compatible. And even if you just assumed that all extensions etc are
> > present, you can't transport arrays / composite types in binary: For
> > hard to discern reasons we a) embed type oids in them b) verify them. b)
> > won't ever work for non-builtin types, because oids are assigned
> > dynamically.
> >
>
> I figured arrays and UDT's would be problematic.

Would it make sense to work toward a binary format that's not
architecture-specific? I recall from COPY that our binary format is
not standardized across, for example, big- and little-endian machines.

Best,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778

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