ALTER SEQUENCE

Description

Modifies the parameters of an existing sequence.

Precautions

Only the owner of a sequence, a user granted the ALTER permission on a sequence, or a user granted the ALTER ANY SEQUENCE permission on a sequence can run the ALTER SEQUENCE command. When separation of duties is disabled, a system administrator has this permission by default. To modify a sequence owner, you must be the sequence owner or system administrator and a member of the new owner role.
In the current version, you can modify only the owner, owning column, maximum value, and cache value. To modify other parameters, delete the sequence and create it again. Then, use the Setval function to restore parameter values.
ALTER SEQUENCE MAXVALUE cannot be used in transactions, functions, and stored procedures.
After the maximum value of a sequence is changed, the cache of the sequence in all sessions is cleared.
If the LARGE identifier is used when a sequence is created, the LARGE identifier must be used when the sequence is altered.
The ALTER SEQUENCE statement blocks the calling of nextval, setval, currval, and lastval.

Syntax

Change the maximum sequence value, owning column, and cache value.

ALTER [ LARGE ] SEQUENCE [ IF EXISTS ] name 
    [MAXVALUE maxvalue | NO MAXVALUE | NOMAXVALUE | CACHE cache]
    [ OWNED BY { table_name.column_name | NONE } ] ;

Change the owner of a sequence.

ALTER [ LARGE ] SEQUENCE [ IF EXISTS ] name OWNER TO new_owner;

Parameters

name
Specifies the name of the sequence to be modified.
IF EXISTS
This option is used when the sequence does not exist. ERROR is not displayed. Instead, a NOTICE message is returned.
MAXVALUE maxvalue | NO MAXVALUE | NOMAXVALUE
Specifies the maximum value of the sequence. The new maximum value must be greater than last_value. If not specified, the old maximum value is retained.

Value range: (last_value, 2⁶³ – 1]. If LARGE is used, the range is (last_value, 2¹²⁷ – 1].
CACHE
Specifies the number of sequences stored in the memory for quick access purposes. If this parameter is not specified, the old cache value is retained.

Value range: [1, 2⁶³ – 1]. If LARGE is used, the range is [1, 2¹²⁷ – 1].
OWNED BY
Associates a sequence with a specified column included in a table. In this way, the sequence will be deleted when you delete its associated column or the table where the column belongs to.

If the sequence has been associated with another table before you use this option, the new association will overwrite the old one.

The associated table and sequence must be owned by the same user and in the same schema.

If OWNED BY NONE is used, all existing associations will be deleted.
new_owner
Specifies the username of the new owner of the sequence. To change the owner, you must also be a direct or indirect member of the new role, and this role must have the CREATE permission on the sequence's schema.

Examples

-- Create an ascending sequence named serial, which starts from 101.
gaussdb=# CREATE SEQUENCE serial START 101;

-- Create a table and specify default values for the sequence.
gaussdb=# CREATE TABLE t1(c1 bigint default nextval('serial'));

-- Change the owning column of serial to T1.C1.
gaussdb=# ALTER SEQUENCE serial OWNED BY t1.c1;

-- Delete a sequence and a table.
gaussdb=# DROP SEQUENCE serial CASCADE;
gaussdb=# DROP TABLE t1;