On Friday, November 9, 2018, Michael Paquier <mich...@paquier.xyz> wrote:
> On Fri, Nov 09, 2018 at 05:28:07PM +0100, Daniel Verite wrote: > > But again COPY is concerned with importing the data that preexists, > > even if it's weird, whereas a psql output formats are not. > > Hm. I checked the contents of the patch in details which provide output > consistent with COPY, but after looking at the global picture I am > getting cold feet on this patch for a couple of reasons: > - This stuff adds new code paths in the frontend mimicking what the > backend already does for years, both doing the same thing. >From the original post: "copy with csv can't help for the output of meta-commands such as \gx, \crosstabview, \l, \d ... whereas a CSV format within psql does work with these." Formatting is usually a client-side concern so this feature fits well there. The fact that we’ve provided a server interface for the same doesn’t preclude its potential desirability in the client. - There are already three ways to fetch data in this format with COPY, > \copy and file_fdw, with all three using the same code paths for option > validations (I can see the arguments at the top of the thread for which > COPY SELECT can actually do everything you want with?). Not always conveniently. > - The experience is confusing, as the psql format uses different options > than the backend to do the same things: Yes, those who use psql need to learn its features. I’d posit that since this syntax is being learned anyway that transferring said knowledge to a newly added csv format will not be confusing. No more so that having to do something that is usually client-side (formatting) on the server in the first place. That we don’t fully replicate the server functionality does’t bother be. This is meant to be a simple and quick ability that handles 95% of use cases and defers to the more powerful server version for the outliers. Feature-wise I’m on board. Given it’s already written I’d say it should go in unless there are code complexity and support concerns - which given the prevalence of other formats I have to believe there are not. David J.
