README

Create Cypher queries in a fluent and easy to understand way via an opinionated builder pattern.

Examples

Simple pattern match example:

This query finds all the colleagues of Alice and Bob:

use PhpGraphGroup\CypherQueryBuilder\QueryBuilder;

$results = QueryBuilder::fromNode('a:Person')
    ->matchingRelationship('a', 'IS_COLLEAGUE', 'b:Person')
    ->whereIn('a.name', ['Alice', 'Bob'])
    ->return('b.name AS name') // Notice of the present tense implies the query gets executed immediately.

The builder runs this query and returns the results:

MATCH (a:Person)-[:IS_COLLEAGUE]->(b:Person)
WHERE a.name IN $names
RETURN b.name AS name

Complex pattern match example

This query contains a more complex pattern that is being built using the pattern builder.

use PhpGraphGroup\CypherQueryBuilder\QueryBuilder;
use PhpGraphGroup\CypherQueryBuilder\Builders\GraphPatternBuilder;

GraphPatternBuilder::from('node:MyNode') // MATCH (node:MyNode)
GraphPatternBuilder::from('MyNode', 'otherNode') // MATCH (otherNode:MyNode)
GraphPatternBuilder::from('myNode:MyNode', 'otherNode') // MATCH (otherNode:MyNode) (TODO: log warning here?)
GraphPatternBuilder::from('Hello') // MATCH (hello:Hello)
GraphPatternBuilder::from('<Hello') // MATCH () <-[hello:Hello]-()
GraphPatternBuilder::from('<Hello')->addChildNode('Heya') // MATCH () <- [hello:Hello] - (heya:Heya)
// TODO: maybe rename this to addNode to allow for a parallel node, aka joining.
// TODO: If a node gets joined by a child node, it should have an anonymous relationship.
GraphPatternBuilder::from('MyNode')->addChildNode('MyOtherNode') // MATCH (myNode:MyNode), (myOtherNode:MyOtherNode)
GraphPatternBuilder::from('MyNode')->addRelationship()->addChildNode('MyOtherNode') // MATCH (myNode:MyNode)--(myOtherNode:MyOtherNode)
GraphPatternBuilder::from(name: 'noLabel') // MATCH (noLabel)
// TODO: Should it inject numbering in the automatic naming? -> no
// TODO: Should we pre-emptively throw an error or let the syntax error be found by the database?
// => first version should stay away from this, but we can revisit.
GraphPatternBuilder::from('MyNode')->addRelationship()->addChildNode('MyNode') // MATCH (myNode:MyNode) - [] -> (myNode:MyNode)

$results = QueryBuilder::from(GraphPatternBuilder::from('node:MyNode')
    ->addRelationship('<Parent')
        ->addChildNode('sibling1:MyNode')->end()
        ->addChildNode('sibling2:MyNode')->end()
    ->end()
    ->addRelationship('Parent>')
        ->addChildNode('grandParent:MyNode')->end()
    ->end()    
)->whereIn('sibling1.name', ['Harry', 'Bart'])
    ->andWhere('sibling2.name', '<>', 'Maria')
    ->andWhere('grandParent.age', '>=', 70)
    ->count('grandParent')

Becomes:

MATCH (node:MyNode), (sibling1:MyNode)

Simple Create example:

Creates a new Person and makes it the colleague of Alice.

use PhpGraphGroup\CypherQueryBuilder\QueryBuilder;

$results = QueryBuilder::new()
    ->matchingNode('a:Person')
    ->where('a.name', '=', 'Alice')
    ->creatingNode('b:Person')
    ->creatingRelationship('a', 'IS_COLLEAGUE', 'b')
    ->create(['b.name' => 'Bob'])

The builder runs this query:

MATCH (a:Person)
WHERE a.name = $param0
CREATE (b:Person), (a)-[:IS_COLLEAGUE]->(b)
SET b.name = $param1

Simple Update example:

How it works

Cypher is an incredible query language that offers great flexibility. However, this flexibility can make it difficult to understand and maintain queries, especially in the form of a query builder.

This library aims to make it easier to write and maintain Cypher queries by providing a fluent builder pattern that is understandable.

It specifically limits the possibilities so the builder is easier to reason about and use. All database actions are still possible, but chaining long and complex clauses after another is not possible anymore.

This is because the main angle and opinion this query builder takes is that long complex multi-clausal queries are not preferred. It is difficult to understand and there is a big chance the performance of the queries will degrade.

The builder has only one of each clause available, and the position of these clauses is fixed:

MATCH { match patterns }
OPTIONAL MATCH* { optional match patterns }
CALL* { subquery }
WHERE { where conditions }

DELETE { deleted variables }
DETACH DELETE { deleted variables }

REMOVE { removed properties & labels }
CREATE { create patterns }
SET { set assignments }
MERGE { merge pattern }
ON CREATE SET { set assignments }
ON MATCH SET { set assignments }

RETURN { return expressions }
ORDER BY { ASC|DESC } { order expressions }
SKIP { skip count }
LIMIT { limit count }

The query builder will only run certain parts of the query depending on which methods you are calling. The methods are intuitive and easy to understand:

There are some cases where UNWIND is used behind the scenes to allow for mass insertions, but that is beyond the scope of this introduction.

Variable Usage

Variables are used to refer to nodes, relationships and aliases. An alias can refer to a property, node, relationship or function call result.

Because of the way the builder structures the query, Cypher will not allow variable reassignment. To maintain flexibility and to allow for raw statements, the query builder to not check for either existance or reassignment of variables. Only after the query is built and sent to the server will an error occur.

Property Usage

Properties refer to properties on a variable. That means that a user should use the dot notation to unambiguously refer to a property. If the does not use a dot notation and refers just to the property, the builder will use it to refer properties on the variable of the entry node or relationship of the builder.

use PhpGraphGroup\CypherQueryBuilder\QueryBuilder;

// Refer unambiguously to the property 'name' on the variable 'p'
$name = QueryBuilder::from('Person', 'p')
    ->where('p.name', '=', 'Alice')
    ->returning('p.name')
    ->only()
// Runs like:
// MATCH (p:Person) WHERE p.name = $param0 RETURN p.name AS name LIMIT 1

// Refer to the property of p without using the dot notation.
$lastNames = QueryBuilder::from('Person', 'p')
    ->where('name', '=', 'Alice')
    ->pluck('lastName')
// Runs like:
// MATCH (p:Person) WHERE p.name = $param0 RETURN p.lastName AS lastName

// Automatically generate a name based on the Label and get al the friends of Alice for over a year.
$friends = QueryBuilder::from('Person')
    ->matchingRelationship('person', 'FRIENDS_WITH', 'friend', 'friendsWith')
    ->matchingNode('Person', 'friend')
    ->where('friendsWith.since', '<=', (new DateTime())->sub(new DateInterval('P1Y')))
    ->andWhere('person.name', '=', 'Alice')
    ->return('friend.name AS name', 'friendsWith.since AS friendsSince')
// Runs like:
// MATCH (person:Person)-[friendsWith:FRIENDS_WITH]->(friend:Person) WHERE friendsWith <= $param0 AND person.name = $param1 RETURN friend.name AS name, friendsWith.since AS friendsSince

php-graph-group / cypher-query-builder

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