Re: Allow COPY to use parameters

On Tue, May 24, 2016 at 3:42 PM, David Fetter <david(at)fetter(dot)org> wrote:
> On Tue, May 24, 2016 at 02:16:40PM -0400, Tom Lane wrote:
>> David Fetter <david(at)fetter(dot)org> writes:
>> > Per discussion on IRC and some test code, COPY can't take parameters
>> > in a PREPARE, which feature would make it even more useful.
>>
>> Uh, what?
>>
>> regression=# prepare foo as copy c from stdin;
>> ERROR: syntax error at or near "copy"
>> LINE 1: prepare foo as copy c from stdin;
>> ^
>>
>> Passing parameters into a utility statement of any stripe is a
>> pretty considerable project, IIRC; the infrastructure isn't there.
>
> Maybe it should be, at least for some of the utility statements.
>
> Please find attached a patch which, according to Andrew Gierth, its
> author, just barely qualifies as a PoC. Yes, it's had to break a
> couple of messages in the regression tests.

Hm, what's the use case preparing COPY? Note, the biggest pain point
I have with COPY is not being able to parameterize the filename
argument. That's pretty easily worked around with a plpgsql wrapper
however.

merlin