Tablespaces in PostgreSQL allow database administrators to define locations in the file system where the files representing database objects can be stored. Once created, a tablespace can be referred to by name when creating database objects. By using tablespaces, an administrator can control the disk layout of a PostgreSQL installation. This is useful in at least two ways. First, if the partition or volume on which the cluster was initialized runs out of space and cannot be extended, a tablespa

When using an external authentication system such as Ident or GSSAPI, the name of the operating system user that initiated the connection might not be the same as the database user that is to be connect as. In this case, a user name map can be applied to map the operating system user name to a database user. To use user name mapping, specify map=map-name in the options field in pg_hba.conf. This option is supported for all authentication methods that receive external user names. Since different

NameCREATE DOMAIN -- define a new domain Synopsis CREATE DOMAIN name [ AS ] data_type [ COLLATE collation ] [ DEFAULT expression ] [ constraint [ ... ] ] where constraint is: [ CONSTRAINT constraint_name ] { NOT NULL | NULL | CHECK (expression) } Description CREATE DOMAIN creates a new domain. A domain is essentially a data type with optional constraints (restrictions on the allowed set of values). The user who defines a domain becomes its owner. If a schema name is give

Namereindexdb -- reindex a PostgreSQL database Synopsis reindexdb [connection-option...] [option...] [ --schema | -S schema ] ... [ --table | -t table ] ... [ --index | -i index ] ... [dbname] reindexdb [connection-option...] [option...] --all | -a reindexdb [connection-option...] [option...] --system | -s [dbname] Description reindexdb is a utility for rebuilding indexes in a PostgreSQL database. reindexdb is a wrapper around the SQL command REINDEX. There is no effective difference be

When you create a table and you realize that you made a mistake, or the requirements of the application change, you can drop the table and create it again. But this is not a convenient option if the table is already filled with data, or if the table is referenced by other database objects (for instance a foreign key constraint). Therefore PostgreSQL provides a family of commands to make modifications to existing tables. Note that this is conceptually distinct from altering the data contained in

Enumerated (enum) types are data types that comprise a static, ordered set of values. They are equivalent to the enum types supported in a number of programming languages. An example of an enum type might be the days of the week, or a set of status values for a piece of data. 8.7.1. Declaration of Enumerated Types Enum types are created using the CREATE TYPE command, for example: CREATE TYPE mood AS ENUM ('sad', 'ok', 'happy'); Once created, the enum type can be used in table and function de

Name psql -- PostgreSQL interactive terminal Synopsis psql [option...] [dbname [username]] Description psql is a terminal-based front-end to PostgreSQL. It enables you to type in queries interactively, issue them to PostgreSQL, and see the query results. Alternatively, input can be from a file or from command line arguments. In addition, psql provides a number of meta-commands and various shell-like features to facilitate writing scripts and automating a wide variety of tasks. Option

The intagg module provides an integer aggregator and an enumerator. intagg is now obsolete, because there are built-in functions that provide a superset of its capabilities. However, the module is still provided as a compatibility wrapper around the built-in functions. F.17.1. Functions The aggregator is an aggregate function int_array_aggregate(integer) that produces an integer array containing exactly the integers it is fed. This is a wrapper around array_agg, which does the same thing for a

19.9.1. Query and Index Statistics Collector These parameters control server-wide statistics collection features. When statistics collection is enabled, the data that is produced can be accessed via the pg_stat and pg_statio family of system views. Refer to Chapter 28 for more information. track_activities (boolean) Enables the collection of information on the currently executing command of each session, along with the time when that command began execution. This parameter is on by default.

To retrieve data from a table, the table is queried. An SQL SELECT statement is used to do this. The statement is divided into a select list (the part that lists the columns to be returned), a table list (the part that lists the tables from which to retrieve the data), and an optional qualification (the part that specifies any restrictions). For example, to retrieve all the rows of table weather, type: SELECT * FROM weather; Here * is a shorthand for "all columns". [1] So the same result woul