ALTER SEQUENCE
ALTER SEQUENCE — change the definition of a sequence generator
Synopsis
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 TO {new_owner
| CURRENT_USER | SESSION_USER } ALTER SEQUENCE [ IF EXISTS ]name
RENAME TOnew_name
ALTER SEQUENCE [ IF EXISTS ]name
SET SCHEMAnew_schema
Description
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.)
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.
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. Ifminvalue
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. Ifmaxvalue
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 futurestart
ALTER SEQUENCE RESTART
commands will use.restart
The optional clause
RESTART [ WITH
changes the current value of the sequence. This is equivalent to calling therestart
]setval
function withis_called
=false
: the specified value will be returned by the next 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
.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 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 optional
NO 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.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. 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
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.
Examples
Restart a sequence called serial
, at 105:
ALTER SEQUENCE serial RESTART WITH 105;
Compatibility
ALTER SEQUENCE
conforms to the SQL standard, except for the START WITH
, OWNED BY
, OWNER TO
, RENAME TO
, and SET SCHEMA
clauses, which are PostgreSQL extensions.