Re: How to get comments for view columns?

eugene(dot)mindrov(at)gmail(dot)com writes:
> is there any way to get comment meta-information for columns in a
> view? I mean, suppose I have several tables and some of their columns
> have comments, then I define a view on these tables, and what I want
> is to somehow retrieve comments (if any) for those columns which are
> selected in a view.
> I tried to play with system catalog tables trying to dig out the
> necessary info, but to no avail.
> The best I could do is to retrieve all "dependent" columns (which
> belong to underlying tables) for a view with their comments, but I
> couldn't find any way to determine a relation between "dependent"
> columns and those actually selected in a view.

What do you consider "selected"? Given a view defined as

select a, b, c+d as sum from tab where e > 42;

what output are you wishing for?

AFAIR the dependency mechanism will treat a,b,c,d,e alike. To do more
you'd need to grovel through the pg_rewrite expression for the view's
select rule, which'd be excruciatingly painful from a client program
for lack of any supporting code.

regards, tom lane