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Why use OGM?

Why GQLAlchemy?

• automate object conversion between graph database objects and Python objects, 
  
• write correct Cypher queries with checks inside IDEs, 
• easily handles setting up Memgraph features like streaming, etc.

Example of defining a node in GQLAlchemy

• Node is a python class that maps to a graph object in Memgraph.
  
• Classes that inherit from Node map to a single label in a graph database.
• In this case the class User maps to the label :User.
• The properties id and name are map to properties of the nodes labelled User in the graph database, their types must be defined and are enforced.
• If the type of the property is missing the Optional keyword, then it cannot be None or missing.
• Field is a function from pydantic that you can use to define constraints in the graph database like uniqueness constraints, indexes and exists constraints.
• Whenever you provide a constraint to the Field function, you have to provide a Memgraph object in the db argument as well, so those constraints can be enforced.
• john1 is a User object that is created and saved to Memgraph in the following openCypher form: (john1 :User {id: 1, name: "John"}).
• john2 is a User object that is created only with an id property, but is then loaded from Memgraph making john1 and john2 represent the same node in Memgraph
• save or load methods set the internal id of the node, in this case john1._id and john2._id to an id that Memgraph uses, that id uniquely defines a node.