constraint.md

Constraint

Constraints are used to enforce specific data schemas within a database.
There are two different types of constraints, one for nodes and one for relationships.
They can be created as following:

use Syndesi\CypherDataStructures\Type\NodeConstraint;
use Syndesi\CypherDataStructures\Type\RelationConstraint;

$nodeConstraint = new NodeConstraint();
$relationConstraint = new RelationConstraint();

// note: the later examples use $someConstraint when the specific type does not matter

!> Important: Constraints are not part of the OpenCypher specification and are different for each database type.

!> Note: The creation of constraints might create internal indexes as well.

Name

The name of constraints must be unique across the whole database.
The name is usually written in lowercase snake case.

// set the name of a constraint:
$someConstraint->setName('some_name');

// get the name of a constraint:
$someConstraint->getName();

For

Constraints are always created for a specific node or relationship label/type.

// set the node label for a node label constraint:
$nodeConstraint->setFor('NodeLabel');

// set the relationship type for a relationship constraint:
$relationConstraint->setFor('RELATIONSHIP_TYPE');

// get the node label or relationship type from a constraint, depending on the constraint type:
$someConstraint->getFor();

Type

Constraints have a specific type, e.g. UNIQUE. These types depend on the database as well as the database version.

!> Important: Depending on the database, not all constraint types are available for nodes as well as relationships.

// set the type of constraint:
$someConstraint->setType('UNIQUE');

// get the type of constraint:
$someConstraint->getType();

Properties

Constraints can specify the properties of a node/relationship on which they should act.

!> Note: Most of the time only the property names are important. Setting the property values to null is therefore ok.

// add property to a constraint with default value null:
$someConstraint->addProperty('propertyName');

// add multiple properties to a constraint:
$someConstraint->addProperties([
    'id' => null,
    'hello' => 'world :D'
]);

// check if a constraint has a specific property:
$someConstraint->hasProperty('id');

// get the value of a specific property:
$someConstraint->getProperty('id');

// get all properties from a constraint:
$someConstraint->getProperties();

// remove a specific property from a constraint:
$someConstraint->removeProperty('hello');

// remove all properties from a constraint:
$someConstraint->removeProperties();

Options

Some constraints can be configured via options.
The example uses strings, but all types (arrays, integers etc.) are supported.

// add a single option
$someConstraint->addOption('name', 'value');

// add multiple options
$someConstraint->addOptions([
    'other.name' => 'other value',
    'some.name' => 'some value'
]);

// check if constraint has option
$someConstraint->hasOption('name');

// get specific option from a constraint
$someConstraint->getOption('name');

// get all options from a constraint
$someConstraint->getOptions();

// remove a specific option from a constraint:
$someConstraint->removeOption('name');

// remove all options from a constraint:
$someConstraint->removeOptions();