SET

Changes the value of a run-time Greenplum Database configuration parameter.

Synopsis

SET [ SESSION | LOCAL ] <configuration_parameter> { TO | = } { <value> | '<value>' | DEFAULT }

SET [SESSION | LOCAL] TIME ZONE { <value> | '<value>' |  LOCAL | DEFAULT }

Description

The SET command changes server configuration parameters. Any configuration parameter classified as a session parameter can be changed on-the-fly with SET. (Some require superuser privileges to change, and others cannot be changed after server or session start.) SET affects only the value used by the current session.

If SET or SET SESSION is issued within a transaction that is later cancelled, the effects of the SET command disappear when the transaction is rolled back. 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.

The effects of SET or SET LOCAL are also canceled by rolling back to a savepoint that is earlier than the command.

If SET LOCAL is used within a function that includes a SET option for the same configuration parameter (see CREATE FUNCTION), the effects of the SET LOCAL command disappear at function exit; the value in effect when the function was called is restored anyway. This allows SET LOCAL to be used for dynamic or repeated changes of a parameter within a function, while retaining the convenience of using the SET option to save and restore the caller's value. Note that a regular SET command overrides any surrounding function's SET option; its effects persist unless rolled back.

See Server Configuration Parameters for information about server parameters.

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. Issuing this outside of a transaction block emits a warning and otherwise has no effect.

configuration_parameter

The name of a settable Greenplum Database run-time configuration parameter. Only parameters classified as session can be changed with SET. See Server Configuration Parameters for details.

value

New value of the parameter. Values can be specified as string constants, identifiers, numbers, or comma-separated lists of these, as appropriate for the particular parameter. DEFAULT can be used to specify resetting the parameter to its default value (that is, whatever value it would have had if no SET had been issued in the current session). If specifying memory sizing or time units, enclose the value in single quotes.

There are a few configuration parameters that can only be adjusted using the SET command or that have a special syntax:

SCHEMA

SET SCHEMA '<value>' is an alias for SET <search_path> TO <value>. Only one schema may be specified using this 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 -1 and 1 inclusive.

You can also set the seed by invoking the setseed() function:

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. Examples of valid values follow:

• 'PST8PDT'
• 'Europe/Rome'
• -7 (time zone 7 hours west from UTC)
• INTERVAL '-08:00' HOUR TO MINUTE (time zone 8 hours west from UTC).

LOCAL

DEFAULT

Set the time zone to your local time zone (that is, server's default value of timezone).

See the Time Zones section of the PostgreSQL documentation for more information about time zones in Greenplum Database.

Examples

Set the schema search path:

SET search_path TO my_schema, public;

Increase the segment host memory per query to 200 MB:

SET statement_mem TO '200MB';

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

SET datestyle TO postgres, dmy;

Set the time zone for San Mateo, California (Pacific Time):

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 Greenplum Database allows more flexible time-zone specifications. All other SET features are Greenplum Database extensions.

See Also

RESET, SHOW

Parent topic: SQL Commands