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ALTER SEQUENCE
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ALTER SEQUENCE

ALTER SEQUENCE — change the definition of a sequence generator

Synopsis

ALTER SEQUENCE [ IF EXISTS ]name    [ ASdata_type ]    [ INCREMENT [ BY ]increment ]    [ MINVALUEminvalue | NO MINVALUE ] [ MAXVALUEmaxvalue | NO MAXVALUE ]    [ START [ WITH ]start ]    [ RESTART [ [ WITH ]restart ] ]    [ CACHEcache ] [ [ NO ] CYCLE ]    [ OWNED BY {table_name.column_name | NONE } ]ALTER SEQUENCE [ IF EXISTS ]name SET { LOGGED | UNLOGGED }ALTER SEQUENCE [ IF EXISTS ]name OWNER TO {new_owner | CURRENT_ROLE | CURRENT_USER | SESSION_USER }ALTER SEQUENCE [ IF EXISTS ]name RENAME TOnew_nameALTER SEQUENCE [ IF EXISTS ]name SET SCHEMAnew_schema

Description

ALTER SEQUENCE changes the parameters of an existing sequence generator. Any parameters not specifically set in theALTER SEQUENCE command retain their prior settings.

You must own the sequence to useALTER SEQUENCE. To change a sequence's schema, you must also haveCREATE privilege on the new schema. To alter the owner, you must be able toSET ROLE to the new owning role, and that role must haveCREATE privilege on the sequence's schema. (These restrictions enforce that altering the owner doesn't do anything you couldn't do by dropping and recreating the sequence. However, a superuser can alter ownership of any sequence anyway.)

Parameters

name

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

IF EXISTS

Do not throw an error if the sequence does not exist. A notice is issued in this case.

data_type

The optional clauseASdata_type changes the data type of the sequence. Valid types aresmallint,integer, andbigint.

Changing the data type automatically changes the minimum and maximum values of the sequence if and only if the previous minimum and maximum values were the minimum or maximum value of the old data type (in other words, if the sequence had been created usingNO MINVALUE orNO MAXVALUE, implicitly or explicitly). Otherwise, the minimum and maximum values are preserved, unless new values are given as part of the same command. If the minimum and maximum values do not fit into the new data type, an error will be generated.

increment

The clauseINCREMENT BYincrement 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 clauseMINVALUEminvalue determines the minimum value a sequence can generate. IfNO MINVALUE is specified, the defaults of 1 and the minimum value of the data type 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 clauseMAXVALUEmaxvalue determines the maximum value for the sequence. IfNO MAXVALUE is specified, the defaults of the maximum value of the data type 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 clauseSTART WITHstart changes the recorded start value of the sequence. This has no effect on thecurrent sequence value; it simply sets the value that futureALTER SEQUENCE RESTART commands will use.

restart

The optional clauseRESTART [ WITHrestart ] changes the current value of the sequence. This is similar to calling thesetval function withis_called =false: the specified value will be returned by thenext call ofnextval. WritingRESTART with norestart value is equivalent to supplying the start value that was recorded byCREATE SEQUENCE or last set byALTER SEQUENCE START WITH.

In contrast to asetval call, aRESTART operation on a sequence is transactional and blocks concurrent transactions from obtaining numbers from the same sequence. If that's not the desired mode of operation,setval should be used.

cache

The clauseCACHEcache 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 optionalCYCLE key word can be used to enable the sequence to wrap around when themaxvalue orminvalue has been reached by an ascending or descending sequence respectively. If the limit is reached, the next number generated will be theminvalue ormaxvalue, respectively.

NO CYCLE

If the optionalNO CYCLE key word is specified, any calls tonextval after the sequence has reached its maximum value will return an error. If neitherCYCLE orNO CYCLE are specified, the old cycle behavior will be maintained.

SET { LOGGED | UNLOGGED }

This form changes the sequence from unlogged to logged or vice-versa (seeCREATE SEQUENCE). It cannot be applied to a temporary sequence.

OWNED BYtable_name.column_name OWNED BY NONE

TheOWNED BY option causes the sequence to be associated with a specific table column, such that if that column (or its whole table) is dropped, the sequence will be automatically dropped as well. If specified, this association replaces any previously specified association for the sequence. The specified table must have the same owner and be in the same schema as the sequence. SpecifyingOWNED BY NONE removes any existing association, making the sequence“free-standing”.

new_owner

The user name of the new owner of the sequence.

new_name

The new name for the sequence.

new_schema

The new schema for the sequence.

Notes

ALTER SEQUENCE will not immediately affectnextval 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 generation parameters. The current backend will be affected immediately.

ALTER SEQUENCE does not affect thecurrval status for the sequence. (BeforePostgreSQL 8.3, it sometimes did.)

ALTER SEQUENCE blocks concurrentnextval,currval,lastval, andsetval calls.

For historical reasons,ALTER TABLE can be used with sequences too; but the only variants ofALTER TABLE that are allowed with sequences are equivalent to the forms shown above.

Examples

Restart a sequence calledserial, at 105:

ALTER SEQUENCE serial RESTART WITH 105;

Compatibility

ALTER SEQUENCE conforms to theSQL standard, except for theAS,START WITH,OWNED BY,OWNER TO,RENAME TO, andSET SCHEMA clauses, which arePostgreSQL extensions.