ALTER SEQUENCE¶
Function¶
Modifies the sequence definition.
Precautions¶
You must be the owner of the sequence to use ALTER SEQUENCE.
In the current version, you can modify only the owner, home column, and the maximum value. To modify other parameters, delete the sequence and create it again. Then, use the Setval function to restore original 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.
ALTER SEQUENCE blocks the invocation of nextval, setval, currval, and lastval.
Syntax¶
Change the maximum value or home column of the sequence.
ALTER SEQUENCE [ IF EXISTS ] name
[ MAXVALUE maxvalue | NO MAXVALUE | NOMAXVALUE ]
[ CACHE cachevalue ]
[ OWNED BY { table_name.column_name | NONE } ] ;
Change the owner of a sequence.
ALTER SEQUENCE [ IF EXISTS ] name OWNER TO new_owner;
Parameter Description¶
name
Specifies the sequence name to be changed.
IF EXISTS
Sends a notification instead of an error when you are modifying a non-existing sequence.
MAXVALUE maxvalue | NO MAXVALUE
Maximum value of a sequence. If NO MAXVALUE is declared, the default value of the ascending sequence is 263-1, and that of the descending sequence is -1. NOMAXVALUE is equivalent to NO MAXVALUE.
CACHE cachevalue
This parameter is supported only by clusters of version 8.2.1.100 or later.
Allocates sequence numbers and stores them in memory for faster access. The minimum value of cachevalue is 1. (One value can be generated at a time, which means NOCACHE.) If this parameter is not specified, the old cache value is retained.
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 field or the table where the field belongs.
If the sequence has been associated with another table before you use this parameter, 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, existing associations will be deleted.
new_owner
Specifies the user name of the new owner. 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¶
Modify the maximum value of serial to 200.
ALTER SEQUENCE serial MAXVALUE 200;
Create a table, and specify default values for the sequence.
CREATE TABLE T1(C1 bigint default nextval('serial'));
Change the owning column of the serial sequence to T1.C1.
ALTER SEQUENCE serial OWNED BY T1.C1;
Change the incremental value and cache value of the serial sequence.
ALTER SEQUENCE serial CACHE 5;