Source: https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/ddl/graph-type/alter-graph-type/
Documentation version: v5.3.2

# ALTER GRAPH TYPE statement

The ALTER GRAPH TYPE statement modifies a graph type in the schema of the current session or a specified schema, including the node types and edge types defined by the graph type.

The following tables list the actions that can be performed on node types and edge types using the ALTER GRAPH TYPE statement.

Node types

 | Action | Description
 | Add node types | Add new node types to the graph type.
 | Drop node types | Remove existing node types from the graph type.
 | Rename node types | Change the name of existing node types.
 | Alter labels | Add or drop labels for node types.
 | - Add Labels | Add new labels to node types.
 | - Drop Labels | Remove labels from node types.
 | Alter properties | Add, drop, rename, or modify properties for node types.
 | - Add Properties | Add new properties to node types.
 | - Drop Properties | Remove properties from node types.
 | - Rename Properties | Change the name of existing properties.
 | - Modify Properties | Change the value type, nullability, or default value of existing properties of node types.

Edge types

 | Action | Description
 | Add edge types | Add new edge types to the graph type.
 | Drop edge types | Remove existing edge types from the graph type.
 | Rename edge types | Change the name of existing edge types.
 | Alter Labels | Add or drop labels for edge types.
 | - Add Labels | Add new labels to edge types.
 | - Drop Labels | Remove labels from edge types.
 | Alter Properties | Add, drop, rename, or modify properties for edge types.
 | - Add Properties | Add new properties to edge types.
 | - Drop Properties | Remove properties from edge types.
 | - Rename Properties | Change the name of existing properties.
 | - Modify Properties | Change the value type, nullability, or default value of existing properties of edge types.

Note

- After a graph type is modified, the nodes and edges in all graphs of that graph type are also modified accordingly. When a node type or edge type is dropped, all nodes or edges of the deleted type are not immediately physically deleted from the Storage service (disk space remains occupied). Instead, they are permanently deleted during the subsequent [RocksDB Compaction](https://github.com/facebook/rocksdb/wiki/Compaction) operations.
- If a property of a node type or edge type is used to create an index, the index is automatically dropped when the property, node type, or edge type is dropped.

Note

An operation involving a non-default schema or an object in it requires access to the schema, either implicitly or through an explicit `USAGE` grant, as well as the privilege required for the operation. The schema access check and the privilege check for the requested operation are independent; satisfying one does not satisfy the other. Schema access control does not apply to temporary graphs or built-in procedures and functions. For more information, see [Schema access control](https://dev-docs.nebula-graph.io/v5.3.2/server-admin/authorization/schema-access-control/).

## Prerequisites

- A graph type is created. For more information, see [CREATE GRAPH TYPE](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/ddl/graph-type/create/).

- To alter a graph type, you must either be the owner of the graph type, be granted to perform the action `ALTER` on the graph type, or be granted to perform the action `ALTER ANY GRAPH TYPE` on the corresponding schema. For more information, see [Roles and privileges](https://dev-docs.nebula-graph.io/v5.3.2/server-admin/authorization/).

## Limitations

- Primary keys

  - The primary key of an existing node type cannot be redefined. Properties cannot be added to, removed from, or replaced in the primary key.
  - `MODIFY PROPERTIES` cannot be used to change the value type, nullability, or default value of a primary key property.
  - Primary keys must be specified when adding new node types.

- Multi-edge keys

  - The multi-edge key of an existing edge type cannot be redefined. Properties cannot be added to, removed from, or replaced in the multi-edge key.
  - `MODIFY PROPERTIES` cannot be used to change the value type, nullability, or default value of a multi-edge key property.
  - Multi-edge keys may be specified when adding new edge types.

- Node types and edge types

  - Each node type or edge type can be altered only once in the same ALTER GRAPH TYPE statement. Example: If a node type is renamed from A to B, you cannot drop node type B or add a new node type named A in the same statement.

- Labels

  - Each label of a node type or edge type can be altered only once in the same ALTER GRAPH TYPE statement. Example: You cannot add label A and drop label A in the same statement.

- Properties

  - Each property of a node type or edge type can be altered only once in the same ALTER GRAPH TYPE statement. Example: If a property is renamed from A to B, you cannot drop property B or add a new property named A in the same statement.
  - When modifying properties:

    - A property referenced by a normal, full-text, or vector index in any graph created from the graph type cannot be modified by using `MODIFY PROPERTIES`. Before modifying the property, drop every index that references it.
    - Changing a property from nullable to not nullable is not allowed.
    - Changes to the value type, nullability, and default value of a property must be made together.
    - Modifications are allowed only when implicit type conversion is possible. For example, changing the value type from INT32 to INT64 is supported. For more information, see [Data type conversions](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/fe/expressions/cast/#data_type_conversions).

## Syntax

diagramsource

 alter_graph_type_statement alter_graph_type_specification node_type_filler primary_key_list edge_type_filler multiedge_key_list alter_element_type_op  

````
alter_graph_type_statement ::= 
    'ALTER'  'PROPERTY'? 'GRAPH TYPE' (schema_reference '/')? graph_type_name '{' alter_graph_type_specification ( ',' alter_graph_type_specification )* '}'

alter_graph_type_specification ::= 
    ADD ('NODE' | 'VERTEX') 'TYPE'? ('IF NOT EXISTS')? node_type_name ( node_type_filler )
    | ADD ('EDGE' | 'RELATIONSHIP') 'TYPE'? ('IF NOT EXISTS')? edge_type_name ('(' source_node_type_name ')' '-[' edge_type_filler ']->' '(' destination_node_type_name ')'
    | '(' destination_node_type_name ')' '<-[' edge_type_filler ']-' '(' source_node_type_name ')'
    | '(' source_node_type_name ')' '~[' edge_type_filler ']~' '(' destination_node_type_name ')')
    | DROP ( ('NODE' | 'VERTEX') | ('EDGE' | 'RELATIONSHIP') ) 'TYPE'? ('IF EXISTS')? element_type_name
    | RENAME ( ('NODE' | 'VERTEX') | ('EDGE' | 'RELATIONSHIP') ) 'TYPE'? old_element_type_name 'TO' new_element_type_name
    | ALTER ( ('NODE' | 'VERTEX') | ('EDGE' | 'RELATIONSHIP') ) 'TYPE'? element_type_name alter_element_type_op+

node_type_filler ::=
    ('LABEL' label_name | ( 'LABELS' | ( 'IS' | ':' ) ) label_name ('&' label_name)*)? 
   ( ('{'   
       (property_name ('::' | 'TYPED')? property_value_type ('NULL' | 'NOT NULL' | 'DEFAULT' value_expression | 'PRIMARY KEY' )*) 
       (',' (property_name ('::' | 'TYPED')? property_value_type ('NULL' | 'NOT NULL' | 'DEFAULT' value_expression| 'PRIMARY KEY' )*))* 
       (',' primary_key_list)?            
    '}')
   ) 

primary_key_list ::=
    'PRIMARY KEY' '(' property_name (',' property_name)* ')'     

edge_type_filler ::=

      ( 'LABEL' label_name | ( 'LABELS' | ( 'IS' | ':' ) ) label_name ('&' label_name)*)? 
      ('{'  
          (property_name ('::' | 'TYPED')? property_value_type ('NULL' | 'NOT NULL' | 'DEFAULT' value_expression | 'MULTIEDGE KEY' )*) 
          (',' (property_name ('::' | 'TYPED')? property_value_type ('NULL' | 'NOT NULL' | 'DEFAULT' value_expression | 'MULTIEDGE KEY')*))* 
          (',' multiedge_key_list)? 
        '}' 
      | '{' ('MULTIEDGE KEY ( )')? '}')

multiedge_key_list ::=
    'MULTIEDGE KEY' '(' (property_name ( ',' property_name)* )? ')' 

alter_element_type_op ::=
    'ADD' 'LABELS' ('IF NOT EXISTS')? label_name ('&' label_name)*
    | 'DROP' 'LABELS' ('IF EXISTS')? label_name ('&' label_name)*
    | 'ADD' 'PROPERTIES' ('IF NOT EXISTS')? '{'  
          (property_name ('::' | 'TYPED')? property_value_type ('NULL' | 'NOT NULL' | 'DEFAULT' value_expression )*) 
          (',' (property_name ('::' | 'TYPED')? property_value_type ('NULL' | 'NOT NULL' | 'DEFAULT' value_expression)*))* '}'
    | 'DROP' 'PROPERTIES' ('IF EXISTS')? '{' property_name (',' property_name)* '}'
    | 'RENAME' 'PROPERTIES' '{' (old_property_name 'TO' new_property_name) (',' (old_property_name 'TO' new_property_name))* '}'
    | 'MODIFY' 'PROPERTIES' '{'  
          (property_name ('::' | 'TYPED')? property_value_type ('NULL' | 'NOT NULL' | 'DEFAULT' value_expression )*) 
          (',' (property_name ('::' | 'TYPED')? property_value_type ('NULL' | 'NOT NULL' | 'DEFAULT' value_expression)*))* '}'

````

## Parameters

### `IF NOT EXISTS`

This clause checks if an element (which may be node type, edge type, label, or property) with the same name already exists. If it does already exist, the element is not added and no exception is thrown.

If you do not specify this clause, an exception is thrown if an element with the same name already exists.

### `schema_reference`

The reference to the path of the schema. It specifies the schema path of the graph type to be altered here.

Both absolute and relative schema paths can be used in the statement. To alter a graph type that resides outside the schema in the current session, the schema path must be specified. For information about setting and viewing the schema, see [SESSION SET](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/sessions/set/) and [SHOW CURRENT_SCHEMA](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/data-admin/show/show-current-schema/).

### `graph_type_name`

The name of the graph type to be altered.

### `node_type_name`

The name of the node type. The name must be unique among all node types and edge types of the graph type.

### `label_name`

The name of the label of the node type or edge type. The name of a label must be unique within a node type or edge type.

### `property_name`

The name of the property of the node type or edge type. The name of a property must be unique within a node type or edge type. However, within a graph type, if multiple properties share a name, these properties must be of the same value type.

### `property_value_type`

The value type of a property of a node type or edge type in the graph type. For more information, see [CREATE GRAPH TYPE](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/ddl/graph-type/create/#property_value_type).

### `primary_key_list`

The list of properties of a node type that functions as the primary key. For more information, see [CREATE GRAPH TYPE](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/ddl/graph-type/create/#primary_key_list).

### `multiedge_key_list`

The list of properties of an edge type based on which the multi-edge key is created. For more information, see [CREATE GRAPH TYPE](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/ddl/graph-type/create/#multiedge_key_list).

### `edge_type_name`

The name of the edge type. The name must be unique among all node types and edge types of the graph type.

### `source_node_type_name`

The name of the source node type of the edge type. The source node type must be one of the node types defined in the graph type.

### `destination_node_type_name`

The name of the destination node type of the edge type. The destination node type must be one of the node types defined in the graph type.

### `IF EXISTS`

This clause checks if the element (which may be node type, edge type, label, or property) to be deleted exists. If it does not exist, the element is not deleted and no exception is thrown.

If you do not specify this clause, an exception is thrown if the element to be deleted does not exist.

### `element_type_name`

The name of the node type or edge type.

### `old_element_type_name`

The current name of the node type or edge type.

### `new_element_type_name`

The new name of the node type or edge type.

### `old_property_name`

The current name of the property.

### `new_property_name`

The new name of the property.

## Examples

The following examples are based on the [example dataset](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/overview/example-dataset/).

### Add a node type and an edge type to a graph type in the current schema

````
'''
ALTER GRAPH TYPE movie_type { 
    ADD NODE TYPE Company (LABEL Company {id INT PRIMARY KEY, name STRING}), 
    ADD EDGE TYPE Serve (Director)-[LABEL Serve{start_year INT, end_year INT}]->(Company) 
}
'''

````

The preceding example adds a node type `Company` and an edge type `Serve` to the graph type `movie_type` in the current schema.

### Add a node type and an edge type to a graph type in a specified schema

````
'''
// Create a schema
CREATE SCHEMA IF NOT EXISTS /my_schema
''' 

'''
// Set the schema for the current session
SESSION SET SCHEMA /my_schema
'''

'''
// Add a node type and an edge type
ALTER GRAPH TYPE /default_schema/movie_type { 
    ADD NODE TYPE Company (LABEL Company {id INT PRIMARY KEY, name STRING}), 
    ADD EDGE TYPE Serve (Director)-[LABEL Serve{start_year INT, end_year INT}]->(Company) 
}
'''

````

The preceding examples add a node type `Company` and an edge type `Serve` to the graph type `movie_type` in the specified schema `/default_schema` when the schema for the current session is set to `/my_schema`.

### Drop a node type and an edge type

````
'''
ALTER GRAPH TYPE movie_type { 
    DROP NODE TYPE Company, 
    DROP EDGE TYPE Serve 
}
'''

````

The preceding example drops the node type `Company` and the edge type `Serve`.

### Rename a node type and an edge type

````
'''
ALTER GRAPH TYPE movie_type { 
    RENAME NODE TYPE Actor TO Actor_renamed, 
    RENAME EDGE TYPE Act TO Act_renamed 
}
'''

````

The preceding example renames the node type `Actor` to `Actor_renamed` and the edge type `Act` to `Act_renamed`.

### Add labels to a node type and an edge type

````
'''
ALTER GRAPH TYPE movie_type { 
    ALTER NODE TYPE `User` ADD LABELS Male&Above30, 
    ALTER EDGE TYPE Watch ADD LABELS InCinema&AtHome 
}
'''

````

The preceding example adds the labels `Male` and `Above30` to the node type `User` and the labels `InCinema` and `AtHome` to the edge type `Watch`.

### Drop labels from a node type and an edge type

````
'''
ALTER GRAPH TYPE movie_type { 
    ALTER NODE TYPE `User` DROP LABELS Male&Above30, 
    ALTER EDGE TYPE Watch DROP LABELS InCinema&AtHome 
}
'''

````

The preceding example drops the labels `Male` and `Above30` from the node type `User` and the labels `InCinema` and `AtHome` from the edge type `Watch`.

### Add properties to a node type and an edge type

````
'''
ALTER GRAPH TYPE movie_type { 
    ALTER NODE TYPE `User` ADD PROPERTIES {email STRING, age INT64}, 
    ALTER EDGE TYPE Watch ADD PROPERTIES {`count` INT64, platform STRING} 
}
'''

````

The preceding example adds the properties `email` and `age` to the node type `User` and the properties `count` and `platform` to the edge type `Watch`.

### Drop properties from a node type and an edge type

````
'''
ALTER GRAPH TYPE movie_type { 
    ALTER NODE TYPE `User` DROP PROPERTIES {email, age}, 
    ALTER EDGE TYPE Watch DROP PROPERTIES {`count`, platform} 
}
'''

````

The preceding example drops the properties `email` and `age` from the node type `User` and the properties `count` and `platform` from the edge type `Watch`.

### Rename properties of a node type and an edge type

````
'''
ALTER GRAPH TYPE movie_type { 
    ALTER NODE TYPE Director RENAME PROPERTIES {birthDate TO birth, name TO lastName }, 
    ALTER EDGE TYPE Watch RENAME PROPERTIES {`rate` TO rating} 
}
'''

````

The preceding example renames the properties `birthDate` and `name` of the node type `Director` to `birth` and `lastName`, respectively, and renames the property `rate` of the edge type `Watch` to `rating`.

### Modify properties of a node type and an edge type

````
'''
ALTER GRAPH TYPE movie_type { 
    ALTER NODE TYPE Director MODIFY PROPERTIES {name STRING DEFAULT "Alex", birthDate DATE DEFAULT date("2016-09-20") },
    ALTER EDGE TYPE Watch MODIFY PROPERTIES {rate FLOAT DEFAULT 4.5} 
}
'''

````

The preceding example modifies the default values of the properties `name` and `birthDate` of the node type `Director` to `Alex` and `2016-09-20"`, respectively, and modifies the default value of the property `rate` of the edge type `Watch` to `4.5`.