ALTER SEQUENCE v11

Name

ALTER SEQUENCE --  change the definition of a sequence generator.

Synopsis

ALTER SEQUENCE <name> [ INCREMENT BY <increment> ]
  [ MINVALUE <minvalue> ] [ MAXVALUE <maxvalue> ]
  [ CACHE <cache> | NOCACHE ] [ CYCLE ]

Description

ALTER SEQUENCE changes the parameters of an existing sequence generator. Any parameter not specifically set in the ALTER SEQUENCE command retains its prior setting.

Parameters

name

The name (optionally schema-qualified) of a sequence to be altered.

increment

The clause INCREMENT BY increment is optional. A positive value will make an ascending sequence, a negative one a descending sequence. If unspecified, the old increment value will be maintained.

minvalue

The optional clause MINVALUE minvalue determines the minimum value a sequence can generate. If not specified, the current minimum value will be maintained. Note that the key words, NO MINVALUE, may be used to set this behavior back to the defaults of 1 and -2⁶³-1 for ascending and descending sequences, respectively, however, this term is not compatible with Oracle databases.

maxvalue

The optional clause MAXVALUE maxvalue determines the maximum value for the sequence. If not specified, the current maximum value will be maintained. Note that the key words, NO MAXVALUE, may be used to set this behavior back to the defaults of 2⁶³-1 and -1 for ascending and descending sequences, respectively, however, this term is not compatible with Oracle databases.

cache

The optional clause CACHE cache specifies how many sequence numbers are to be preallocated and stored in memory for faster access. The minimum value is 1 (only one value can be generated at a time, i.e., NOCACHE). If unspecified, the old cache value will be maintained.

CYCLE

The CYCLE option allows the sequence to wrap around when the maxvalue or minvalue has been reached by an ascending or descending sequence respectively. If the limit is reached, the next number generated will be the minvalue or maxvalue, respectively. If not specified, the old cycle behavior will be maintained. Note that the key words, NO CYCLE, may be used to alter the sequence so that it does not recycle, however, this term is not compatible with Oracle databases.

Notes

To avoid blocking of concurrent transactions that obtain numbers from the same sequence, ALTER SEQUENCE is never rolled back; the changes take effect immediately and are not reversible.

ALTER SEQUENCE will not immediately affect NEXTVAL results in backends, other than the current one, that have pre-allocated (cached) sequence values. They will use up all cached values prior to noticing the changed sequence parameters. The current backend will be affected immediately.

Examples

Change the increment and cache value of sequence, serial.

ALTER SEQUENCE serial INCREMENT BY 2 CACHE 5;

See Also

CREATE SEQUENCE, DROP SEQUENCE