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

2009/11/24 Hannu Krosing <hannu(at)2ndquadrant(dot)com>:
> On Tue, 2009-11-24 at 05:00 -0800, Daniel Farina wrote:
>> On Tue, Nov 24, 2009 at 4:37 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>
>> > then syntax should be:
>> >
>> > COPY table TO streamname(parameters)
>> >
>> > COPY table TO filestream('/tmp/foo.dta') ...
>> > COPY table TO dblinkstream(connectionstring) ...
>
> You probably meant
>
> COPY table TO dblinkstream(connectionstring, table)
>
> ?
>
>> I like this one quite a bit...it's a bit like an aggregate, except the
>> initial condition can be set in a rather function-callish way.
>>
>> But that does seem to require making a DDL command, which leaves a
>> nice green field.
>
> not necessarily DDL, maybe just a "copystream" type and a set of
> functions creating objects of that type.
>
> if you make it a proper type with input and output function, then you
> can probably use it in statements like this
>
> COPY table TO (select stream::copystream from streams where id = 7);
>
> COPY table TO 'file:/tmp/outfile':: copystream;
>
> COPY table TO 'dblink::<connectstring>':: copystream;

it interesting - but still you have to have DDL for declaring stream.
It is analogous to function:

CREATE FUNCTION ....

SELECT 'foo'::regprocedure

but syntax COPY table TO copystream is good idea. I like it.

>
>> In particular, we could then make as many hooks,
>> flags, and options as we wanted, but sometimes there is a paradox of
>> choice...I just did not want to anticipate on Postgres being friendly
>> to a new DDL command when writing this the first time.
>
> fulltext lived for quite some time as set of types and functions before
> it was glorified with its own DDL syntax.

What is DDL? Wrapper for insert to system catalog.

so we can have table pg_catalog.copystream

and for first testing

CREATE OR REPLACE FUNCTION register_copystream(regproc, regproc, regproc ...)

if we will happy - than it is one day work for support statement

CREATE COPYSTREAM ( ...

Regards
Pavel Stehule

>
> It may be good to have the same approach here - do it as a set of types
> and functions first, think about adding DDL once it has stabilised
> enough
>
>
> --
> Hannu Krosing   http://www.2ndQuadrant.com
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