PostgreSQL 8.0.0rc4 Documentation
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# ALTER SEQUENCE

## Name

ALTER SEQUENCE -- change the definition of a sequence generator

## Synopsis

    ALTER SEQUENCE name [ INCREMENT [ BY ] increment ]
        [ MINVALUE minvalue | NO MINVALUE ] [ MAXVALUE maxvalue | NO MAXVALUE ]
        [ RESTART [ WITH ] start ] [ CACHE cache ] [ [ NO ] 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`
`NO MINVALUE`

  The optional clause `MINVALUE `minvalue`` determines the minimum value a sequence can generate. If `NO MINVALUE` is specified, the defaults of 1 and -263-1 for ascending and descending sequences, respectively, will be used. If neither option is specified, the current minimum value will be maintained.

`maxvalue`
`NO MAXVALUE`

  The optional clause `MAXVALUE `maxvalue`` determines the maximum value for the sequence. If `NO MAXVALUE` is specified, the defaults are 263-1 and -1 for ascending and descending sequences, respectively, will be used. If neither option is specified, the current maximum value will be maintained.

`start`

  The optional clause `RESTART WITH `start`` changes the current value of the sequence.

`cache`

  The clause `CACHE `cache`` enables sequence numbers 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., no cache). If unspecified, the old cache value will be maintained.

CYCLE

  The optional `CYCLE` key word may be used to enable 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.

NO CYCLE

  If the optional `NO CYCLE` key word is specified, any calls to `nextval` after the sequence has reached its maximum value will return an error. If neither `CYCLE` or `NO CYCLE` are specified, the old cycle behaviour will be maintained.

## Examples

Restart a sequence called `serial`, at 105:

    ALTER SEQUENCE serial RESTART WITH 105;

## 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 preallocated (cached) sequence values. They will use up all cached values prior to noticing the changed sequence parameters. The current backend will be affected immediately.

## Compatibility

`ALTER SEQUENCE` conforms with SQL:2003.

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