52.15. pg_database
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## 52.15. pg_database #

The catalog pg_database stores information about the available databases. Databases are created with the CREATE DATABASE command. Consult Chapter 22 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 52.15. pg_database Columns

Column Type Description
`oid` oid Row identifier
`datname` name Database name
`datdba` oid (references 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)
`datlocprovider` char Locale provider for this database: `b` = builtin, `c` = libc, `i` = icu
`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.
`dathasloginevt` bool Indicates that there are login event triggers defined for this database. This flag is used to avoid extra lookups on the pg_event_trigger table during each backend startup. This flag is used internally by PostgreSQL™ and should not be manually altered or read for monitoring purposes.
`datconnlimit` int4 Sets maximum number of concurrent connections that can be made to this database. -1 means no limit, -2 indicates the database is invalid.
`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_xact` to be shrunk. It is the minimum of the per-table pg_class.`relfrozenxid` values.
`datminmxid` xid All multixact 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 multixact ID wraparound or to allow `pg_multixact` to be shrunk. It is the minimum of the per-table pg_class.`relminmxid` values.
`dattablespace` oid (references 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.
`datcollate` text LC_COLLATE for this database
`datctype` text LC_CTYPE for this database
`datlocale` text Collation provider locale name for this database. If the provider is `libc`, `datlocale` is `NULL`; `datcollate` and `datctype` are used instead.
`daticurules` text ICU collation rules for this database
`datcollversion` text Provider-specific version of the collation. This is recorded when the database is created and then checked when it is used, to detect changes in the collation definition that could lead to data corruption.
`datacl` aclitem[] Access privileges; see Section 5.8 for details

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