48.15. pg_database
The catalog pg_database stores information about the available databases. Databases are created with the CREATE DATABASE command. Consult Глава 21 for details about the meaning of some of the parameters.
Unlike most system catalogs, pg_database is shared across all databases of a cluster: there is only one copy of pg_database per cluster, not one per database.
Table 48-15. pg_database Columns
| Name | Type | References | Description |
|---|---|---|---|
| oid | oid | Row identifier (hidden attribute; must be explicitly selected) | |
| datname | name | Database name | |
| datdba | oid | pg_authid.oid | Owner of the database, usually the user who created it |
| encoding | int4 | Character encoding for this database (pg_encoding_to_char() can translate
this number to the encoding name) |
|
| datcollate | name | LC_COLLATE for this database | |
| datctype | name | LC_CTYPE for this database | |
| datistemplate | bool | If true, then this database can be cloned by any user with CREATEDB privileges; if false, then only superusers or the owner of the database can clone it. | |
| datallowconn | bool | If false then no one can connect to this database. This is used to protect the template0 database from being altered. | |
| datconnlimit | int4 | Sets maximum number of concurrent connections that can be made to this database. -1 means no limit. | |
| datlastsysoid | oid | Last system OID in the database; useful particularly to pg_dump | |
| datfrozenxid | xid | All transaction IDs before this one have been replaced with a permanent ("frozen") transaction ID in this database. This is used to track whether the database needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_clog to be shrunk. It is the minimum of the per-table pg_class.relfrozenxid values. | |
| datminmxid | xid | All multitransaction IDs before this one have been replaced with a transaction ID in this database. This is used to track whether the database needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_clog to be shrunk. It is the minimum of the per-table pg_class.relminmxid values. | |
| dattablespace | oid | pg_tablespace.oid | The default tablespace for the database. Within this database, all tables for which pg_class.reltablespace is zero will be stored in this tablespace; in particular, all the non-shared system catalogs will be there. |
| datacl | aclitem[] | Access privileges; see GRANT and REVOKE for details |