Re: R: feature proposal ...

On Thursday 2005-09-22 13:16, Andrew Dunstan wrote:
> Jim C. Nasby wrote:
> >While I'm all for COPY from views, I think I'd rather have the syntactic
> >warts than code warts. ISTM that
> >
> >CREATE TEMP VIEW some_name AS SELECT * FROM table WHERE ...;
> >COPY some_name TO stdout;
> >
> >is much uglier than
> >
> >COPY SELECT * FROM table WHERE ... TO stdout;
>
> They aren't mutually exclusive, though. And once you have code in place
> for the first part, turning the direct query case into a temp_view+copy
> is arguably just a case of syntactic sugar. I do think the direct query
> should at least be parenthesized, if we go that way.

Definitely any SELECT that might occur in COPY should be a sub-select. It
should meet any syntactic restrictions on a sub-select and it should be in
parentheses (or for the liberal, implied parentheses).

Proposed:
o Allow COPY to output from views
-- Pending "Allow COPY to output from views", Allow COPY to output from
subqueries.

The rationale being that all subqueries can be the create clause of a views.

> So why not do what everyone is agreed on now? Whatever happens the work
> won't be wasted.
>
> Also, as nifty as this might be, we should also be prepared for people
> to complain that it runs a lot slower than vanilla COPY, because it
> surely will.

Why would there be a material difference in speed in the case of a simple
projection?

For example

Given
CREATE TABLE foo
( col_0
,col_1
, .
, .
,col_2N)

Then
COPY
(SELECT col_0
,col_2
, .
, .
,col_2N)
TO
file-like-target