ALTER SEQUENCE() SQL Commands ALTER SEQUENCE()
NAME
ALTER SEQUENCE - change the definition of a sequence generator
SYNOPSIS
ALTER SEQUENCE name [ INCREMENT [ BY ] increment ]
[ MINVALUE minvalue | NO MINVALUE ] [ MAXVALUE maxvalue | NO MAXVALUE ]
[ RESTART [ WITH ] start ] [ CACHE cache ] [ [ NO ] CYCLE ]
[ OWNED BY { table.column | NONE } ]
ALTER SEQUENCE name RENAME TO new_name
ALTER SEQUENCE name SET SCHEMA new_schema
DESCRIPTION
ALTER SEQUENCE changes the parameters of an existing sequence genera-
tor. 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.
PARAMETERS
name The name (optionally schema-qualified) of a sequence to be
altered.
increment
The clause INCREMENT BY increment is optional. A positive value
will make an ascending sequence, a negative one a descending
sequence. If unspecified, the old increment value will be main-
tained.
minvalue
NO MINVALUE
The optional clause MINVALUE minvalue determines the minimum
value a sequence can generate. If 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 maxvalue determines the maximum
value for the sequence. If 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 start changes the current value
of the sequence. This is equivalent to calling the setval func-
tion with is_called = false: the specified value will be
returned by the next call of nextval.
cache The clause CACHE cache enables sequence numbers to be preallo-
cated 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 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.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, mak-
ing the sequence ``free-standing''.
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, RENAME, 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.)
Some variants of ALTER TABLE can be used with sequences as well; for
example, to rename a sequence it is also possible to use ALTER TABLE
RENAME.
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 OWNED BY,
RENAME, and SET SCHEMA clauses, which are PostgreSQL extensions.
SEE ALSO
CREATE SEQUENCE [create_sequence(l)], DROP SEQUENCE [drop_sequence(l)]
SQL - Language Statements 2008-09-19 ALTER SEQUENCE()
postgresql 8.3.4 - Generated Thu Oct 2 08:13:14 CDT 2008