ALTER SEQUENCE — change the definition of a sequence generator
ALTER SEQUENCE [ IF EXISTS ]name
[ 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
OWNER TOnew_owner
ALTER SEQUENCE [ IF EXISTS ]name
RENAME TOnew_name
ALTER SEQUENCE [ IF EXISTS ]name
SET 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 also be a direct or indirect member of 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.)
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.
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
minvalue
, NO MINVALUE
The optional clause MINVALUE
determines
the minimum value a sequence can generate. If minvalue
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
determines
the maximum value for the sequence. If maxvalue
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 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 ALTER SEQUENCE RESTART commands will use.
start
restart
The optional clause RESTART [ WITH
changes the
current value of the sequence. This is equivalent 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.
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
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.
OWNED BY
table_name
.column_name
, OWNED 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_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.
To avoid blocking of concurrent transactions that obtain numbers from the
same sequence, ALTER SEQUENCE's effects on the sequence
generation parameters are never rolled back; those changes take effect
immediately and are not reversible. However, the OWNED BY
,
OWNER TO
, RENAME TO
, and SET SCHEMA
clauses cause ordinary catalog updates that can be rolled back.
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.)
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.