ALTER SEQUENCE — change the definition of a sequence generator
ALTER SEQUENCEname
[ INCREMENT [ BY ]increment
] [ MINVALUEminvalue
| NO MINVALUE ] [ MAXVALUEmaxvalue
| NO MAXVALUE ] [ RESTART [ WITH ]start
] [ CACHEcache
] [ [ NO ] CYCLE ] [ OWNED BY {table
.column
| NONE } ] ALTER SEQUENCEname
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.
name
The name (optionally schema-qualified) of a sequence to be altered.
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 RESTART WITH
changes the
current value of the sequence.
start
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 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 behavior will be
maintained.
OWNED BY
table
.column
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_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
and SET SCHEMA
clauses are ordinary
catalog updates and 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.
Some variants of ALTER TABLE
can be used with
sequences as well; for example, to rename a sequence use ALTER
TABLE RENAME
.