Closed Graph

Overview

The closed graph is constrained by its graph type (or schema), which imposes a strict framework that governs data insertion: nodes and edges with schemas or properties not defined cannot be added. While the graph type can be altered after a graph is created, its defined data model ensures consistent structure, guaranteeing high data integrity and consistency.

In a closed graph,

• Each node or edge belongs to exactly one schema.
• Each schema is associated with a set of properties; each property is defined with a specific value type.

For closed graphs, node and edge schemas, along with their properties, must be explicitly defined. This definition can occur either during graph creation or later, and can be easily altered as necessary throughout the graph's lifecycle.

Creating Closed Graph

Empty Graph Type

To create a graph g1 with an empty graph type:

GQL
CREATE GRAPH g1

The graph g1 is created as a closed graph, containing only the built-in default node schema and default edge schema.

Customized Graph Type

To create a graph g2 with a graph type specification, which defines:

• Node schema User with properties name (STRING type) and age (UINT32 type).
• Node schema Club with a property name (STRING type).
• Edge schema Follows with a property createdOn (LOCAL DATETIME type).
• Edge schema Joins with no properties.

GQL
CREATE GRAPH g2 { 
  NODE User ({name STRING, age UINT32}),
  NODE Club ({name STRING}),
  EDGE Follows ()-[{createdOn LOCAL DATETIME}]->(),
  EDGE Joins ()-[]->()
}

Defined Graph Type

To create a graph g3 based on the defined graph type named gType (How to manage graph types), you have three equivalent GQL options to specify the graph type to be used:

GQL
CREATE GRAPH g3 gType

or

GQL
CREATE GRAPH g3 :: gType

or

GQL
CREATE GRAPH g3 TYPED gType

The graph g3 is created with all the schemas and properties defined within the graph type gType.

Graph Type of Another Graph

To create a graph g4 by copying the graph type of an existing graph trans:

GQL
CREATE GRAPH g4 LIKE trans

The LIKE keyword specifies the graph whose graph type is to be copied. The graph g4 is created with the same schemas and properties defined within the graph trans.

Managing Graph Types

The graph type defines structural rules for graphs by outlining the allowed node and edge schemas, and their associated properties. You can define and store graph types in the database, making them reusable when creating new graphs.

Showing Graph Types

To show graph types defined in the database:

GQL
SHOW GRAPH TYPE

Each graph type provides the following essential metadata:

Creating Graph Type

To create a graph type gType:

GQL
CREATE GRAPH TYPE gType { 
  NODE User ({name STRING, age UINT32}),
  NODE Club ({name STRING}),
  EDGE Follows ()-[{createdOn LOCAL DATETIME}]->(),
  EDGE Joins ()-[]->()
}

Dropping Graph Type

To drop the graph type gType:

GQL
DROP GRAPH TYPE gType

The IF EXISTS clause is used to prevent errors when attempting to delete a graph type that does not exist. It allows the statement to be safely executed.

GQL
DROP GRAPH TYPE IF EXISTS gType

This deletes the graph type gType only if a graph type with that name does exist. If gType does not exist, the statement is ignored without throwing an error.

Encrypting Properties

When creating a closed graph or a graph type, you can configure any property to be encrypted using one of the supported encryption methods: AES128, AES256, RSA and ECC.

To create a graph g5, encrypting the name property of the node schema User:

GQL
CREATE GRAPH g5 { 
  NODE User ({name STRING encrypt("AES128"), age UINT32}),
  NODE Club ({name STRING}),
  EDGE Follows ()-[{createdOn LOCAL DATETIME}]->(),
  EDGE Joins ()-[]->()
}

To create a graph type gType_1, encrypting the name property of the node schema User:

GQL
CREATE GRAPH TYPE gType_1 { 
  NODE User ({name STRING encrypt("AES128"), age UINT32}),
  NODE Club ({name STRING}),
  EDGE Follows ()-[{createdOn LOCAL DATETIME}]->(),
  EDGE Joins ()-[]->()
}

Showing Schemas and Properties

To show node schemas defined in the current graph:

GQL
SHOW NODE SCHEMA

To show edge schemas defined in the current graph:

GQL
SHOW EDGE SCHEMA

To show properties associated with the node schema User in the current graph:

GQL
SHOW NODE User PROPERTY

To show properties associated with the edge schema Joins in the current graph:

GQL
SHOW EDGE Joins PROPERTY

Each schema provides the following essential metadata:

Each property provides the following essential metadata:

Adding Schemas and Properties

You can add new schemas and properties within a closed graph.

To add node schemas User and Club within the graph g1:

GQL
ALTER GRAPH g1 ADD NODE {
  User ({username STRING, gender STRING}),
  Club ({name STRING, score FLOAT})
}

To add an edge schema Follows within the graph g1:

GQL
ALTER GRAPH g1 ADD EDGE {
  Follows ()-[{createdOn DATE}]->()
}

To add a property tags to the node schema User within the current graph:

GQL
ALTER NODE user ADD PROPERTY {tags LIST<STRING>}

To add properties distance and weight to the edge schema links within the current graph:

GQL
ALTER EDGE links ADD PROPERTY {
  distance FLOAT, 
  weight DECIMAL(10,5)
}

You can add properties to all node or edge schemas. For example, to add a property when to all edge schemas within the current graph:

GQL
ALTER EDGE * ADD PROPERTY {when DATE}

Altering Schemas

You can alter the name and comment of a schema in the current graph.

To rename the node schema School to University in the current graph:

GQL
ALTER NODE School RENAME TO University

To rename the edge schema Follows to Follow in the current graph:

GQL
ALTER EDGE Follows RENAME TO Follow

To update the comment of the node schema User in the current graph:

GQL
ALTER NODE User COMMENT "Self-registration"

To update the comment of the edge schema Follows in the current graph:

GQL
ALTER EDGE Follows COMMENT "From user to user"

You can perform both operations in a single statement:

GQL
ALTER NODE User RENAME TO User_s2 COMMENT "Self-registration"

Altering Properties

You can alter the name and comment of a property in the current graph.

To rename the property name to username for User nodes in the current graph:

GQL
ALTER NODE User name RENAME TO username

To rename the property createdOn to startDate for Follows edges in the current graph:

GQL
ALTER EDGE Follows createdOn RENAME TO startDate

To update the comment for the name property of User nodes in the current graph:

GQL
ALTER NODE User name COMMENT "Contains 5 to 64 characters"

To update the comment for the createdOn property of Follows edges in the current graph:

GQL
ALTER EDGE Follows createdOn COMMENT "When the relationship is established"

You can perform both operations in a single statement:

GQL
ALTER EDGE Follows createdOn RENAME TO startDate COMMENT "When the relationship is established"

Dropping Schemas and Properties

You can delete schemas and properties from a graph.

• Dropping a schema: Deleting a node or edge schema also deletes all nodes or edges that belong to that schema. Note that this deletion of nodes automatically triggers the removal of all edges connected to them. The two built-in default schemas cannot be dropped.
• Dropping a property: When a property is dropped, all related data - including the property values, associated indexes, and cached values - is permanently removed.

The schema dropping operation runs as a job, you may run SHOW JOB <id?> afterward to verify its completion.

To drop the node schema User from the graph g1:

GQL
ALTER GRAPH g1 DROP NODE User 

To drop edge schemas Follows and StudyAt from the graph g1:

GQL
ALTER GRAPH g1 DROP EDGE Follows, StudyAt 

To drop properties name and age from User nodes in the current graph:

GQL
ALTER NODE User DROP PROPERTY name, age

To drop the property when from links edges in the current graph:

GQL
ALTER EDGE links DROP PROPERTY when

To drop the property location from all nodes in the current graph:

GQL
ALTER NODE * DROP PROPERTY location