Relationships¶

This guide covers querying graph relationships using nested field selections in GraphQL.

Nested Selections¶

In Grafeo, nested fields in a GraphQL query map to edge traversals. The field name corresponds to the edge type:

{
  Person(name: "Alice") {
    name
    friends {
      name
      age
    }
  }
}

This query:

1. Finds nodes with label Person where name = "Alice"
2. Returns the name property
3. Traverses outgoing friends edges
4. Returns name and age of connected nodes

How Nesting Maps to the Graph¶

Multi-Level Nesting¶

Query multiple levels of relationships:

{
  Person(name: "Alice") {
    name
    friends {
      name
      friends {
        name
      }
    }
  }
}

This traverses two hops: Alice's friends, then their friends.

Filtering Nested Results¶

Apply arguments to nested fields to filter related nodes:

{
  Person(name: "Alice") {
    name
    friends(age: 30) {
      name
      age
    }
  }
}

Multiple Relationship Types¶

Query different relationship types in the same query:

{
  Person(name: "Alice") {
    name
    friends {
      name
    }
    colleagues {
      name
      company
    }
  }
}

Python Example¶

import grafeo

db = grafeo.GrafeoDB()

# Create a social graph
db.execute("INSERT (:Person {name: 'Alice', age: 30})")
db.execute("INSERT (:Person {name: 'Bob', age: 25})")
db.execute("INSERT (:Person {name: 'Charlie', age: 35})")
db.execute("""
    MATCH (a:Person {name: 'Alice'}), (b:Person {name: 'Bob'})
    INSERT (a)-[:friends]->(b)
""")
db.execute("""
    MATCH (b:Person {name: 'Bob'}), (c:Person {name: 'Charlie'})
    INSERT (b)-[:friends]->(c)
""")

# Query relationships
result = db.execute_graphql("""
{
  Person(name: "Alice") {
    name
    friends {
      name
      friends {
        name
      }
    }
  }
}
""")
for row in result:
    print(row)

Rust Example¶

use grafeo_engine::GrafeoDB;

let db = GrafeoDB::new_in_memory();

// Create data
db.execute("INSERT (:Person {name: 'Alice'})").unwrap();
db.execute("INSERT (:Person {name: 'Bob'})").unwrap();
db.execute(
    "MATCH (a:Person {name: 'Alice'}), (b:Person {name: 'Bob'}) INSERT (a)-[:friends]->(b)"
).unwrap();

// Query with nested relationships
let result = db.execute_graphql(r#"
{
  Person(name: "Alice") {
    name
    friends {
      name
    }
  }
}
"#).unwrap();