GRAPH.CONSTRAINT CREATE

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

Available in:

Redis Stack / Graph 2.12.0

Time complexity:

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.

RedisGraph 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 constrainted 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 folllows:

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

Required arguments

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:

redis> GRAPH.QUERY g "CREATE INDEX FOR (p:Person) ON (p.first_name, p.last_name)"
1) 1) "Indices created: 2"
   2) "Cached execution: 0"
   3) "Query internal execution time: 25.779500 milliseconds"
redis> GRAPH.CONSTRAINT CREATE g UNIQUE NODE Person PROPERTIES 2 first_name last_name
PENDING

Since RedisGraph 2.12 indexes are constructed asynchronously. The constraint construction will start once the index is fully constructed.

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:

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

Deleting a constraint

See GRAPH.CONSTRAINT DROP

Listing constraints

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

GRAPH.RO_QUERY <key> "CALL db.constraints()"

For each constraint the procedure will yield the following fields:

Example:

redis> GRAPH.RO_QUERY g "call db.constraints()"
1) 1) "type"
   2) "label"
   3) "properties"
   4) "entitytype"
   5) "status"
2) 1) 1) "UNIQUE"
      2) "Person"
      3) "[birthdate]"
      4) "NODE"
      5) "UNDER CONSTRUCTION"
   2) 1) "MANDATORY"
      2) "Person"
      3) "[first_name, last_name]"
      4) "NODE"
      5) "OPERATIONAL"