# `ALTER SEQUENCE`
<a name="alter-sequence-syntax-support"></a>

`ALTER SEQUENCE` — change the definition of a sequence generator.

**Important**  
When using sequences, the cache value should be carefully considered. For more information, see the Important callout on the [`CREATE SEQUENCE`](create-sequence-syntax-support.md) page.  
For guidance on how best to use sequences based on workload patterns, see [Working with sequences and identity columns](sequences-identity-columns-working-with.md).

## Supported syntax
<a name="alter-sequence-supported-syntax"></a>

```
ALTER SEQUENCE [ IF EXISTS ] name
    [ INCREMENT [ BY ] increment ]
    [ MINVALUE minvalue | NO MINVALUE ] [ MAXVALUE maxvalue | NO MAXVALUE ]
    [ [ NO ] CYCLE ]
    [ START [ WITH ] start ]
    [ RESTART [ [ WITH ] restart ] ]
    [ CACHE cache ]
    [ OWNED BY { table_name.column_name | NONE } ]
ALTER SEQUENCE [ IF EXISTS ] name OWNER TO { new_owner | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
ALTER SEQUENCE [ IF EXISTS ] name RENAME TO new_name
ALTER SEQUENCE [ IF EXISTS ] name SET SCHEMA new_schema

where cache is 1 or cache >= 65536
```

## Description
<a name="alter-sequence-description"></a>

`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. To alter the owner, you must be able to `SET ROLE` to the new owning role, and that role must have `CREATE` privilege on the sequence's schema. (These restrictions enforce that altering the owner doesn't do anything you couldn't do by dropping and recreating the sequence. However, a superuser can alter ownership of any sequence anyway.)

## Parameters
<a name="alter-sequence-parameters"></a>

***name***  
The name (optionally schema-qualified) of a sequence to be altered.

**`IF EXISTS`**  
Do not throw an error if the sequence does not exist. A notice is issued in this case.

***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 maintained.

***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 the minimum value of the data type 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 of the maximum value of the data type and -1 for ascending and descending sequences, respectively, will be used. If neither option is specified, the current maximum 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.

***start***  
The optional clause `START WITH start` changes the recorded start value of the sequence. This has no effect on the current sequence value; it simply sets the value that future `ALTER SEQUENCE RESTART` commands will use.

***restart***  
The optional clause `RESTART [ WITH restart ]` changes the current value of the sequence. This is similar to calling the `setval` function with `is_called` = `false`: the specified value will be returned by the next call of `nextval`. Writing `RESTART` with no *restart* value is equivalent to supplying the start value that was recorded by `CREATE SEQUENCE` or last set by `ALTER SEQUENCE START WITH`.  
In contrast to a `setval` call, a `RESTART` operation on a sequence is transactional and blocks concurrent transactions from obtaining numbers from the same sequence. If that's not the desired mode of operation, `setval` should be used.

***cache***  
The clause `CACHE cache` enables sequence numbers to be preallocated and stored in memory for faster access. The value must be either 1 or some value >= 65536. If unspecified, the old cache value will be maintained. For more information about cache behavior, see the guidance under [`CREATE SEQUENCE`](create-sequence-syntax-support.md).

**`OWNED BY table_name.column_name` / `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\$1owner***  
The user name of the new owner of the sequence.

***new\$1name***  
The new name for the sequence.

***new\$1schema***  
The new schema for the sequence.

## Notes
<a name="alter-sequence-notes"></a>

`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.

`ALTER SEQUENCE` may cause other transactions to OCC.

For historical reasons, `ALTER TABLE` can be used with sequences too; but the only variants of `ALTER TABLE` that are allowed with sequences are equivalent to the forms shown above.

## Examples
<a name="alter-sequence-examples"></a>

Restart a sequence called `serial`, at 105:

```
ALTER SEQUENCE serial RESTART WITH 105;
```

## Compatibility
<a name="alter-sequence-compatibility"></a>

`ALTER SEQUENCE` conforms to the SQL standard, except for the `AS`, `START WITH`, `OWNED BY`, `OWNER TO`, `RENAME TO`, and `SET SCHEMA` clauses, which are PostgreSQL extensions.