02_property_graph

Example 02 — Property graph

What it demonstrates

Building a labelled property graph (LPG): declaring an optional schema, attaching labels and typed properties to nodes, running label- and property-indexed MATCH-style queries, and — the other half of the round trip — reading the typed properties back out of each matched node with lpg.Graph.GetNodeProperty.

Domain / scenario

A tiny social graph of five people. Each person node carries:

• the Person label, and the Admin label as well for administrators;
• a name string property and an age int64 property.

alice   (Person, Admin)  name=alice    age=30   -> bob, charlie
bob     (Person)         name=bob      age=25   -> dave
charlie (Person)         name=charlie  age=30
dave    (Person, Admin)  name=dave     age=42
erin    (Person)         name=erin     age=28

The example runs three queries: all Admin nodes, all Person nodes aged exactly 30, and the one-hop out-neighbours of the admins. For every matched node it then fetches the name and age properties and prints them alongside the node key, so the report shows both which nodes matched and what they hold. Each result group is sorted, so the output is fully deterministic.

How to run

go run ./examples/02_property_graph

Expected output

All Admins:
  alice    name=alice    age=30
  dave     name=dave     age=42
Persons aged 30:
  alice    name=alice    age=30
  charlie  name=charlie  age=30
One-hop out from Admins:
  bob      name=bob      age=25
  charlie  name=charlie  age=30

Key APIs

• graph/lpg.New — build a labelled property graph over the mutable adjacency-list backend.
• graph/lpg/schema.New / Schema.RegisterLabel / Schema.RegisterProperty — declare the labels and typed property keys the graph expects.
• graph/lpg.Graph.SetNodeLabel / SetNodeProperty — attach labels and typed property values to nodes.
• graph/lpg.Int64Value / StringValue — construct the typed property values written to the graph.
• graph/lpg.Graph.GetNodeProperty and PropertyValue.String / PropertyValue.Int64 — read the typed properties back off each matched node.
• graph/query.New / Engine.Match / Pattern.Vertex / Pattern.Out / Pattern.Collect — run the label- and property-indexed MATCH-style query.
• graph/query.WithLabel / WithProperty — the label and property predicates that drive the indexed match.
• graph/csr.BuildFromAdjList — freeze the live graph into the immutable CSR snapshot the query engine reads.

Further reading

• graph/lpg — the labelled-property-graph package documentation
• graph/lpg/schema — schema declaration and validation
• graph/query — the indexed MATCH-style query engine
• Example 01 — basic shortest paths — the prior example, building the flow this one extends
• docs/examples-standard.md — the standard every example follows