GRAPH.CONSTRAINT CREATE

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syntax: | GRAPH.CONSTRAINT CREATE key MANDATORY|UNIQUE NODE label | RELATIONSHIP reltype PROPERTIES propCount prop [prop...]

Creates a graph constraint.

Examples

Introduction to constraints

A constraint is a rule enforced on graph nodes or relationships, used to guarantee a certain structure of the data.

FalkorDB supports two types of constraints:

1. Mandatory constraints
2. Unique constraints

Mandatory constraints

A mandatory constraint enforces existence of given attributes for all nodes with a given label or for all edges with a given relationship-type.

Consider a mandatory constraint over the attribute id of all nodes with the label Person. This constraint will enforce that any Person node in the graph has an id attribute. Any attempt to create or modify a Person node, such that the resulting node does not have an id attribute, will fail.

Unique constraints

A unique constraint enforces uniqueness of values of a given set of attributes for all nodes with a given label or for all edges with a given relationship-type. I.e., no duplicates are allowed.

Consider a unique constraint over the attributes: first_name and last_name of all nodes with the label Person This constraint will enforce that any combination of first_name, last_name is unique. E.g., a graph can contain the following Person nodes:

(:Person {first_name:'Frank', last_name:'Costanza'})
(:Person {first_name:'Estelle', last_name:'Costanza'})

But trying to create a third node with first_name Frank and last_name Costanza, will issue an error and the query will fail.

Notes:

• A unique constraint requires the existence of an exact-match index prior to its creation. For example, trying to create a unique constraint governing attributes: first_name and last_name of nodes with label Person without having an exact-match index over Person's first_name and last_name attributes will fail.

• A unique constraint is enforced for a given node or edge only if all the constrained properties are defined (non-null).

• Unique constraints are not enforced for array-valued properties.

• Trying to delete an index that supports a constraint will fail.

Creating a constraint

To create a constraint, use the GRAPH.CONSTRAINT CREATE command as follows:

GRAPH.CONSTRAINT CREATE key constraintType {NODE label | RELATIONSHIP reltype} PROPERTIES propCount prop [prop...]

Required arguments

key

is key name for the graph.

constraintType

is the constraint type: either MANDATORY or UNIQUE.

NODE label | RELATIONSHIP reltype

is the graph entity type (NODE or RELATIONSHIP) and the name of the node label or relationship type on which the constraint should be enforced.

propCount

is the number of properties following. Valid values are between 1 and 255.

prop...

is a list of propCount property names.

note

Notes:

• Constraints are created asynchronously. The constraint creation command will reply with PENDING and the newly created constraint is enforced gradually on all relevant nodes or relationships. During its creation phase, a constraint's status is UNDER CONSTRUCTION. When all governed nodes or relationships confirm to the constraint - its status is updated to OPERATIONAL, otherwise, if a conflict is detected, the constraint status is updated to FAILED and the constraint is not enforced. The caller may try to resolve the conflict and recreate the constraint. To retrieve the status of all constraints - use the db.constraints() procedure.

• A constraint creation command may fail synchronously due to the following reasons:

  1. Syntax error
  2. Constraint already exists
  3. Missing supporting index (for unique constraint)

  In addition, a constraint creation command may fail asynchronously due to the following reasons:

  1. The graph contains data which violates the constraint

Return value

@simple-string-reply - PENDING if executed correctly and the constraint is being created asynchronously, or @error-reply otherwise.

Examples

Creating a unique constraint for a node label

To create a unique constraint for all nodes with label Person enforcing uniqueness on the combination of values of attributes first_name and last_name, issue the following commands:

Python

from falkordb import FalkorDB
client = FalkorDB()
graph = client.select_graph('g')
graph.query("CREATE INDEX FOR (p:Person) ON (p.first_name, p.last_name)")
result = client.create_constraint('g', 'UNIQUE', 'NODE', 'Person', ['first_name', 'last_name'])
print(result)

Javascript

import { FalkorDB } from 'falkordb';
const client = await FalkorDB.connect();
const graph = client.selectGraph('g');
await graph.query("CREATE INDEX FOR (p:Person) ON (p.first_name, p.last_name)");
const result = await client.createConstraint('g', 'UNIQUE', 'NODE', 'Person', ['first_name', 'last_name']);
console.log(result);

Rust

let client = FalkorDB::connect_default();
let graph = client.select_graph("g");
graph.query("CREATE INDEX FOR (p:Person) ON (p.first_name, p.last_name)")?;
let result = client.create_constraint("g", "UNIQUE", "NODE", "Person", &["first_name", "last_name"])?;
println!("{}", result);

Java

FalkorDB client = new FalkorDB();
Graph graph = client.selectGraph("g");
graph.query("CREATE INDEX FOR (p:Person) ON (p.first_name, p.last_name)");
String result = client.createConstraint("g", "UNIQUE", "NODE", "Person", Arrays.asList("first_name", "last_name"));
System.out.println(result);

Shell

redis> GRAPH.QUERY g "CREATE INDEX FOR (p:Person) ON (p.first_name, p.last_name)"
redis> GRAPH.CONSTRAINT CREATE g UNIQUE NODE Person PROPERTIES 2 first_name last_name
# Output: PENDING

Creating a mandatory constraint for a relationship type

To create a mandatory constraint for all edges with relationship-type Visited, enforcing the existence of a date attribute, issue the following command:

Python

result = client.create_constraint('g', 'MANDATORY', 'RELATIONSHIP', 'Visited', ['date'])
print(result)

Javascript

const result = await client.createConstraint('g', 'MANDATORY', 'RELATIONSHIP', 'Visited', ['date']);
console.log(result);

Rust

let result = client.create_constraint("g", "MANDATORY", "RELATIONSHIP", "Visited", &["date"])?;
println!("{}", result);

Java

String result = client.createConstraint("g", "MANDATORY", "RELATIONSHIP", "Visited", Arrays.asList("date"));
System.out.println(result);

Shell

redis> GRAPH.CONSTRAINT CREATE g MANDATORY RELATIONSHIP Visited PROPERTIES 1 date
# Output: PENDING

Listing constraints

To list all constraints enforced on a given graph, use the db.constraints procedure:

Python

result = graph.ro_query("call db.constraints()")
print(result)

Javascript

const result = await graph.ro_query("call db.constraints()");
console.log(result);

Rust

let result = graph.ro_query("call db.constraints()")?;
println!("{:?}", result);

Java

ResultSet result = graph.ro_query("call db.constraints()");
System.out.println(result);

Shell

redis> GRAPH.RO_QUERY g "call db.constraints()"
# Output: ...

Deleting a constraint

See GRAPH.CONSTRAINT DROP