Re: PostgreSQL :: Catalog Query

Yogi S schrieb am 18.07.2018 um 12:22:
> this might look quite naive. but I see quite a difference in between other RDBMS database vs PostgreSQL.
> usually the categorization of the entities are like what is stated below. I am sure mysql follows the same.
>
> Cluster --> Catalog --> database --> Schema --> tables
>
> but in postgreSQL the catalog <--> database relation is quite one-to-one.
> Question is, is it safe to assume that postgreSQL does not have any /*catalog concept*/ as such.

As far as the SQL standard is concerned Postgres' databases do map to the term "catalog" .

The only difference (or deviation from the standard) is, that they are no real "namespaces".
In the SQL standard a fully qualified (table) name consists of three parts:

catalog.schema.table

however in Postgres the catalog (while it exists as a "thing") is not allowed to be used in a fully qualified name.

So in Postgres it's indeed:

"Cluster" (or "Instance") -> Databases -> Schemas -> Tables

MySQL only has databases (or catalogs) but no schemas - or schemas, but no catalogs as "database" is a synonym for "schema" there.
And MySQL has no "cluster" the way the term is used in Postgres. So in MySQL it's only

"Instance" -> Databases -> Tables

Note that in Oracle this is again completely different. And in DB2.

The only DBMS I know of that actually supports these two namespaces (catalogs, schemas) completely is SQL Server (a catalog is called a "database" there)

But this shouldn't be posted or discussed on the "bugs" mailing list, as it is not a bug.