PostgreSQL - SQL Language Reference

PostgreSQL Reference Manual - Volume 1 - SQL Language Reference
by The PostgreSQL Global Development Group
Paperback (6"x9"), 716 pages
ISBN 0954612027
RRP £32.00 ($49.95)

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PostgreSQL Reference Manual
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12.101 SET

Name

SET -- change a run-time parameter

Synopsis

SET [ SESSION | LOCAL ] configuration_parameter { TO | = } {
 value | 'value' | DEFAULT }
SET [ SESSION | LOCAL ] TIME ZONE { timezone | LOCAL | DEFAULT }

Description

The SET command changes run-time configuration parameters. Many of the run-time parameters listed in Volume 3: Server Configuration can be changed on-the-fly with SET. (But some require superuser privileges to change, and others cannot be changed after server or session start.) SET only affects the value used by the current session.

If SET or SET SESSION is issued within a transaction that is later aborted, the effects of the SET command disappear when the transaction is rolled back. (This behavior represents a change from PostgreSQL versions prior to 7.3, where the effects of SET would not roll back after a later error.) Once the surrounding transaction is committed, the effects will persist until the end of the session, unless overridden by another SET.

The effects of SET LOCAL last only till the end of the current transaction, whether committed or not. A special case is SET followed by SET LOCAL within a single transaction: the SET LOCAL value will be seen until the end of the transaction, but afterwards (if the transaction is committed) the SET value will take effect.

Parameters

SESSION: Specifies that the command takes effect for the current session. (This is the default if neither SESSION nor LOCAL appears.)
LOCAL: Specifies that the command takes effect for only the current transaction. After COMMIT or ROLLBACK, the session-level setting takes effect again. Note that SET LOCAL will appear to have no effect if it is executed outside a BEGIN block, since the transaction will end immediately.
configuration_parameter: Name of a settable run-time parameter. Available parameters are documented in Volume 3: Server Configuration and below.
value: New value of parameter. Values can be specified as string constants, identifiers, numbers, or comma-separated lists of these. DEFAULT can be used to specify resetting the parameter to its default value.

Besides the configuration parameters documented in Volume 3: Server Configuration, there are a few that can only be adjusted using the SET command or that have a special syntax:

NAMES

SET NAMES value is an alias for SET client_encoding TO value.

SEED

Sets the internal seed for the random number generator (the function random). Allowed values are floating-point numbers between 0 and 1, which are then multiplied by 2³¹-1. The seed can also be set by invoking the function setseed:

SELECT setseed(value);

TIME ZONE

SET TIME ZONE value is an alias for SET timezone TO value. The syntax SET TIME ZONE allows special syntax for the time zone specification. Here are examples of valid values:

'PST8PDT': The time zone for Berkeley, California.
'Europe/Rome': The time zone for Italy.
-7: The time zone 7 hours west from UTC (equivalent to PDT). Positive values are east from UTC.
INTERVAL '-08:00' HOUR TO MINUTE: The time zone 8 hours west from UTC (equivalent to PST).
LOCAL
DEFAULT: Set the time zone to your local time zone (the one that the server's operating system defaults to).

See section 6.5.3 Time Zones for more information about time zones.

Notes

The function set_config provides equivalent functionality. See section 7.20 System Administration Functions.

Examples

Set the schema search path:

SET search_path TO my_schema, public;

Set the style of date to traditional POSTGRES with “day before month” input convention:

SET datestyle TO postgres, dmy;

Set the time zone for Berkeley, California:

SET TIME ZONE 'PST8PDT';

Set the time zone for Italy:

SET TIME ZONE 'Europe/Rome';

Compatibility

SET TIME ZONE extends syntax defined in the SQL standard. The standard allows only numeric time zone offsets while PostgreSQL allows more flexible time-zone specifications. All other SET features are PostgreSQL extensions.