From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | eugene(dot)mindrov(at)gmail(dot)com |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: How to get comments for view columns? |
Date: | 2007-05-04 03:49:25 |
Message-ID: | 9933.1178250565@sss.pgh.pa.us |
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Lists: | pgsql-general |
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
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