Value expressions are used in a variety of contexts, such as in the target list of the SELECT command, as new column values in INSERT or UPDATE, or in search conditions in a number of commands. The result of a value expression is sometimes called a scalar, to distinguish it from the result of a table expression (which is a table). Value expressions are therefore also called scalar expressions (or even simply expressions). The expression syntax allows the calculation of values from primitive par

Namevacuumdb -- garbage-collect and analyze a PostgreSQL database Synopsis vacuumdb [connection-option...] [option...] [ --table | -t table [( column [,...] )] ] ... [dbname] vacuumdb [connection-option...] [option...] --all | -a Description vacuumdb is a utility for cleaning a PostgreSQL database. vacuumdb will also generate internal statistics used by the PostgreSQL query optimizer. vacuumdb is a wrapper around the SQL command VACUUM. There is no effective difference between vacuuming

NameVALUES -- compute a set of rows Synopsis VALUES ( expression [, ...] ) [, ...] [ ORDER BY sort_expression [ ASC | DESC | USING operator ] [, ...] ] [ LIMIT { count | ALL } ] [ OFFSET start [ ROW | ROWS ] ] [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ] Description VALUES computes a row value or set of row values specified by value expressions. It is most commonly used to generate a "constant table" within a larger command, but it can be used on its own. W

The data type uuid stores Universally Unique Identifiers (UUID) as defined by RFC 4122, ISO/IEC 9834-8:2005, and related standards. (Some systems refer to this data type as a globally unique identifier, or GUID, instead.) This identifier is a 128-bit quantity that is generated by an algorithm chosen to make it very unlikely that the same identifier will be generated by anyone else in the known universe using the same algorithm. Therefore, for distributed systems, these identifiers provide a bet

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

NameVACUUM -- garbage-collect and optionally analyze a database Synopsis VACUUM [ ( { FULL | FREEZE | VERBOSE | ANALYZE | DISABLE_PAGE_SKIPPING } [, ...] ) ] [ table_name [ (column_name [, ...] ) ] ] VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ table_name ] VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] ANALYZE [ table_name [ (column_name [, ...] ) ] ] Description VACUUM reclaims storage occupied by dead tuples. In normal PostgreSQL operation, tuples that are deleted or obsoleted by an update are

The uuid-ossp module provides functions to generate universally unique identifiers (UUIDs) using one of several standard algorithms. There are also functions to produce certain special UUID constants. F.45.1. uuid-ossp Functions Table F-33 shows the functions available to generate UUIDs. The relevant standards ITU-T Rec. X.667, ISO/IEC 9834-8:2005, and RFC 4122 specify four algorithms for generating UUIDs, identified by the version numbers 1, 3, 4, and 5. (There is no version 2 algorithm.) Eac

This section discusses how to upgrade your database data from one PostgreSQL release to a newer one. PostgreSQL major versions are represented by the first two digit groups of the version number, e.g., 8.4. PostgreSQL minor versions are represented by the third group of version digits, e.g., 8.4.2 is the second minor release of 8.4. Minor releases never change the internal storage format and are always compatible with earlier and later minor releases of the same major version number, e.g., 8.4.

NameUNLISTEN -- stop listening for a notification Synopsis UNLISTEN { channel | * } Description UNLISTEN is used to remove an existing registration for NOTIFY events. UNLISTEN cancels any existing registration of the current PostgreSQL session as a listener on the notification channel named channel. The special wildcard * cancels all listener registrations for the current session. NOTIFY contains a more extensive discussion of the use of LISTEN and NOTIFY. Parameters channel Name

NameUPDATE -- update rows of a table Synopsis [ WITH [ RECURSIVE ] with_query [, ...] ] UPDATE [ ONLY ] table_name [ * ] [ [ AS ] alias ] SET { column_name = { expression | DEFAULT } | ( column_name [, ...] ) = ( { expression | DEFAULT } [, ...] ) | ( column_name [, ...] ) = ( sub-SELECT ) } [, ...] [ FROM from_list ] [ WHERE condition | WHERE CURRENT OF cursor_name ] [ RETURNING * | output_expression [ [ AS ] output_name ] [, ...] ] Descrip