Re: [SQL] Expression with aggregate

In PostgreSQL a view is a table with a special rule named: "_RETnametable" where
nametable stands for the table name used by the view.

eg:
CREATE RULE "_RETvista" AS ON SELECT TO "vista" DO INSTEAD SELECT "a" FROM
"tabella";

Actually, psql checks in the field pg_class.relkind to see if it is a table or
other kind of class ('i'=index, S=sequence, 'r'=table/view, etc).
If psql finds a 'r' into pg_class.relkind then it checks in the boolean field
pg_class.relhasrules and prints "table" if its value is FALSE or "view?" if its
value is TRUE.
The field pg_class.relhasrules is also used for every kind of rule in the table,
this is the reason why psql prints "view?" because it doesn't know for sure if
the rule is
a "_RET..." (view) or other kind of rule.

QUERY: SELECT usename, relname, relkind, relhasrules FROM pg_class, pg_user WHER
E usesysid = relowner and ( relkind = 'r' OR relkind = 'i' OR relkind = 'S') and
relname !~ '^pg_' and (relkind != 'i' OR relname !~ '^xinx') ORDER BY relname

Database = prova
+------------------+----------------------------------+----------+
| Owner | Relation | Type |
+------------------+----------------------------------+----------+
| postgres | serial | sequence |
| postgres | t_a_seq | sequence |
| postgres | tabella | table |
| postgres | vista | view? |
+------------------+----------------------------------+----------+

There's an exactly way to know if the table is a view or a table; the function
pg_get_viewdef()
But I don't know why psql doesn't use it...

prova=> select pg_get_viewdef('vista');
pg_get_viewdef
--------------------------
SELECT "a" FROM "tabella";
(1 row)

prova=> select pg_get_viewdef('tabella');
pg_get_viewdef
--------------
Not a view
(1 row)

José

Bruce Momjian ha scritto:

> >
> > That should provide the desired results. As for the
> > question about the view in the \d output, I don't know
> > why its like that, I've wondered myself.
>
> I think it is view? because it could be a view, or a rule?
>
> > >
> > > By the way, when I use \d to list the tables, why is
> > > a view always
> > > shown with a '?' like in
> > >
> > > asdf=> \d
> > > Database = asdf
> > >
> > >
> > +------------------+----------------------------------+----------+
> > > | Owner | Relation
> > > | Type |
> > >
> > >
> > +------------------+----------------------------------+----------+
> > > | albert | a
> > > | table |
> > > | albert | b
> > > | table |
> > > | albert | c
> > > | view? |
> > >
> > >
> > +------------------+----------------------------------+----------+
> > >
> > > ? Why doesn't it just say '| albert | c | view |'?
> > >
> > > I'd really appreciate any hints with this, even
> > > though I know how to
> > > do it (as demonstrated above) with the use of the
> > > view.
> > >
> > > Thanks in advance for your help,
> > >
> > > Albert.
> > >
> > > --
> > >
> > >
> > ---------------------------------------------------------------------------
> > > Post an / Mail to / Skribu al: Albert Reiner
> > > <areiner(at)tph(dot)tuwien(dot)ac(dot)at>
> > >
> > ---------------------------------------------------------------------------
> > >
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> >
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>
> --
> Bruce Momjian | http://www.op.net/~candle
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