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47.15. pg_database

The catalog pg_database stores information about the available databases. Databases are created with the CREATE DATABASE command. Consult Chapter 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 47-15. 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 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
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

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