The catalog pg_database stores information about the available databases. Databases are created with the CREATE DATABASE command. Consult Chapter 19 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 42-15. pg_database Columns
|datdba||oid||pg_authid.oid||Owner of the database, usually the user who created it|
|encoding||int4||Character encoding for this database|
|datistemplate||bool||If true then this database can be used in the TEMPLATE clause of CREATE DATABASE to create a new database as a clone of this one.|
|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|
|datvacuumxid||xid||All rows inserted or deleted by transaction IDs before this one have been marked as known committed or known aborted in this database. This is used to determine when commit-log space can be recycled.|
|datfrozenxid||xid||All rows inserted by transaction IDs before this one have been relabeled with a permanent ("frozen") transaction ID in this database. This is useful to check whether a database must be vacuumed soon to avoid transaction ID wrap-around problems.|
|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.|
|datconfig||text||Session defaults for run-time configuration variables|
|datacl||aclitem||Access privileges; see GRANT and REVOKE for details.|