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, and maximum 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.
• The ALTER SEQUENCE statement blocks the calling of nextval, setval, currval, and lastval.

Syntax

• Change the owning column and maximum value of a sequence.

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

• Change the owner of a sequence.

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ALTER 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 the current maximum value stored by GTM. If this parameter is not specified, the original maximum value is retained.

  Value range: (gtm_last_value, 2⁶³ –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

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-- 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;

Helpful Links

CREATE SEQUENCE and DROP SEQUENCE