Re: PostgreSQL 7.4.2 new tables [Stupid Query]

On Sat, 20 Mar 2004, V i s h a l Kashyap @ [Sai Hertz And Control Systems] wrote:

> Dear all,
>
> Just migrated to PostgreSQL 7.4.2 from 7.3.4
>
> I found that  after migration to 7.4.2  some of the tables in my
> database  which were not  created by me exists their
> Namely :
> 1. information_schema.sql_features
> 2. information_schema.sql_implementation_info
> 3. information_schema.sql_languages
> 4. information_schema.sql_packages
> 5  information_schema.sql_sizing
> 6. information_schema.sql_sizing_profiles
>
> These tables are viewable only with the psqlODBC connected clients i.e
> when I connect to database with
> psqlODBC then only these tables are viewable.

> My Stupid question is  :
> 1. Is this normal.
> 2. If this is normal then what are these tables for ?

It's part of the SQL spec.  It's the standard way to get information
about the database.

For example, from information_schema.sql_features, you can determine
things like, we support LEFT OUTER JOIN but not CUBE and ROLLUP. From
sql_implementation_info you can see things like the fact that NULLs are
treated as greater than non-nulls for sorting purposes.  From tables
(which isn't mentioned above, but should exists) you can see table names
and whether they are base tables or views.

They're not generally as powerful as going to the pg_* tables (some
details are likely to be left out), but they're standard.