Re: [PATCH 4/4] Add tests to dblink covering use of COPY TO FUNCTION

On Thu, Nov 26, 2009 at 6:13 PM, David Fetter <david@fetter.org> wrote:
> It'd be nice to make this available to the next revision of DBI-Link
> and it'll be pretty handy for our SQL/MED whenever that happens.

Okay, so this thread sort of wandered into how we could refactor other
elements of COPY.  Do we have a good sense on what we should do to the
current patch (or at least the idea represented by it) to get it into
a committable state within finite time?

I think adding a bytea and/or text mode is once such improvement...I
am still reluctant to give up on INTERNAL because the string buffer
passed in the INTERNAL scenario is ideal for C programmers -- the
interface is even simpler than dealing with varlena types.  But I
agree that auxiliary modes should exist to enable easier hacking.

The thorniest issue in my mind is how state can be initialized
retained and/or modified between calls to the bytestream-acceptance
function.

Arguably it is already in a state where it is no worse than dblink,
which itself has a global hash table to manage state.

Also, if you look carefully at the dblink test suite I submitted,
you'll see an interesting trick: one can COPY from multiple sources
consecutively to a single COPY on a remote node when in text mode
(binary mode has a header that cannot be so neatly catenated).  This
is something that's pretty hard to enable with any automatic
startup-work-cleanup approach.

fdr