ALTER SEQUENCE — change the definition of a sequence generator
ALTER SEQUENCE [ IF EXISTS ]name[ ASdata_type] [ INCREMENT [ BY ]increment] [ MINVALUEminvalue| NO MINVALUE ] [ MAXVALUEmaxvalue| NO MAXVALUE ] [ [ NO ] CYCLE ] [ START [ WITH ]start] [ RESTART [ [ WITH ]restart] ] [ CACHEcache] [ OWNED BY {table_name.column_name| NONE } ] ALTER SEQUENCE [ IF EXISTS ]nameSET { LOGGED | UNLOGGED } ALTER SEQUENCE [ IF EXISTS ]nameOWNER TO {new_owner| CURRENT_ROLE | CURRENT_USER | SESSION_USER } ALTER SEQUENCE [ IF EXISTS ]nameRENAME TOnew_nameALTER SEQUENCE [ IF EXISTS ]nameSET SCHEMAnew_schema
ALTER SEQUENCE changes the parameters of an existing
sequence generator. Any parameters not specifically set in the
ALTER SEQUENCE command retain their prior settings.
You must own the sequence to use ALTER SEQUENCE.
To change a sequence's schema, you must also have CREATE
privilege on the new schema.
To alter the owner, you must be able to SET ROLE to the
new owning role, and that role must have CREATE
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.)
nameThe name (optionally schema-qualified) of a sequence to be altered.
IF EXISTSDo not throw an error if the sequence does not exist. A notice is issued in this case.
data_type
The optional
clause AS
changes the data type of the sequence. Valid types are
data_typesmallint, integer,
and bigint.
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 using NO
MINVALUE or NO 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 clause INCREMENT BY 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.
increment
minvalueNO MINVALUE
The optional clause MINVALUE determines
the minimum value a sequence can generate. If minvalueNO
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.
maxvalueNO MAXVALUE
The optional clause MAXVALUE determines
the maximum value for the sequence. If maxvalueNO
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.
CYCLE
The optional CYCLE key word can 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 behavior will be
maintained.
start
The optional clause START WITH changes the
recorded start value of the sequence. This has no effect on the
current sequence value; it simply sets the value
that future startALTER SEQUENCE RESTART commands will use.
restart
The optional clause RESTART [ WITH changes the
current value of the sequence. This is similar to calling the
restart ]setval function with is_called =
false: the specified value will be returned by the
next call of nextval.
Writing RESTART with no restart value is equivalent to supplying
the start value that was recorded by CREATE SEQUENCE
or last set by ALTER SEQUENCE START WITH.
In contrast to a setval call,
a RESTART 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 clause 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.
cache
SET { LOGGED | UNLOGGED }This form changes the sequence from unlogged to logged or vice-versa (see CREATE SEQUENCE). It cannot be applied to a temporary sequence.
OWNED BY table_name.column_nameOWNED BY NONE
The OWNED 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.
Specifying OWNED BY NONE removes any existing
association, making the sequence “free-standing”.
new_ownerThe user name of the new owner of the sequence.
new_nameThe new name for the sequence.
new_schemaThe new schema for the sequence.
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 generation parameters. The current backend will be affected
immediately.
ALTER SEQUENCE does not affect the currval
status for the sequence. (Before PostgreSQL
8.3, it sometimes did.)
ALTER SEQUENCE blocks
concurrent nextval, currval,
lastval, and setval calls.
For historical reasons, ALTER TABLE can be used with
sequences too; but the only variants of ALTER TABLE
that are allowed with sequences are equivalent to the forms shown above.
Restart a sequence called serial, at 105:
ALTER SEQUENCE serial RESTART WITH 105;
ALTER SEQUENCE conforms to the SQL
standard, except for the AS, START WITH,
OWNED BY, OWNER TO, RENAME TO, and
SET SCHEMA clauses, which are
PostgreSQL extensions.