How to get the OID of a view

stan <stanb@panix.com> writes:

I am trying to write a query to return the names, and data types of all the
columns in a view. It has been pointed out to me that the best approach
would be using pg_catalog. OK, so I found pg_view, which I can get the names
of a the views from and pg_attribute which can give me the column names,
but it looks like i need to join this on OID, and pg_table does not have
that data.

Yeah, pg_tables is just a user-friendly view, it's not really that
useful for programmatic work. I'd look directly at pg_class and
pg_attribute for this problem.

A good way to learn what to do is to see what psql does for its
various \d commands --- if you start it with the -E option you'll
see the underlying SQL it issues. It'll likely be more complicated
than you want, but you can strip away what's not useful for you.

regards, tom lane

Hello
--------------

On 22.05.2020, at 18:15, stan <stanb@panix.com> wrote:

I am trying to write a query to return the names, and data types of all the
columns in a view. It has been pointed out to me that the best approach
would be using pg_catalog. OK, so I found pg_view, which I can get the names
of a the views from and pg_attribute which can give me the column names,
but it looks like i need to join this on OID, and pg_table does not have
that data.

--
"They that would give up essential liberty for temporary safety deserve
neither liberty nor safety."
-- Benjamin Franklin

You find the oid of the views in pg_catalog.pg_class (relkind 'v').

Regards
Charles

On 5/22/20 9:15 AM, stan wrote:

I am trying to write a query to return the names, and data types of all the
columns in a view. It has been pointed out to me that the best approach
would be using pg_catalog. OK, so I found pg_view, which I can get the names
of a the views from and pg_attribute which can give me the column names,
but it looks like i need to join this on OID, and pg_table does not have
that data.

I'm guessing you mean pg_tables.

In any case, go straight to the source pg_class:

\dv
List of relations
Schema | Name | Type | Owner
--------+------------------+------+----------
public | tag_litem | view | postgres
public | tag_short_status | view | postgres

select oid, relname, relkind from pg_class where relname = 'tag_litem';
oid | relname | relkind
-------+-----------+---------
60558 | tag_litem | v

Where relkind = 'v' means view:

https://www.postgresql.org/docs/12/catalog-pg-class.html

--
Adrian Klaver
adrian.klaver@aklaver.com

On Fri, May 22, 2020 at 9:15 AM stan <stanb@panix.com> wrote:

I am trying to write a query to return the names, and data types of all the
columns in a view. It has been pointed out to me that the best approach
would be using pg_catalog. OK, so I found pg_view, which I can get the
names
of a the views from and pg_attribute which can give me the column names,
but it looks like i need to join this on OID, and pg_table does not have
that data.

The table you want is pg_class:

https://www.postgresql.org/docs/12/catalog-pg-class.html

If the system views listed in [1]https://www.postgresql.org/docs/12/views-overview.html don't provide you what you need you need
to fall-back to the system tables listed in [2]https://www.postgresql.org/docs/12/catalogs-overview.html.

[1]: https://www.postgresql.org/docs/12/views-overview.html
[2]: https://www.postgresql.org/docs/12/catalogs-overview.html

David J.