README
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Example 22 — Cypher engine
What it demonstrates
The GoGraph Cypher engine — the module's flagship, 100% compliant with
the openCypher TCK at the execution level. It runs four Cypher idioms
against a small social graph: a label scan with a property projection and
ORDER BY, a WHERE filter, a directed relationship pattern, and a
CREATE inside a write transaction. Every value is read back from the
result record and printed in human-readable form (names and ages), never
as a raw node ID.
Domain / scenario
A tiny social graph of five people. Each Person node carries a name
and an age; directed relationships connect them:
(Alice {age:30}) -[:KNOWS]-> (Bob {age:25})
(Bob {age:25}) -[:KNOWS]-> (Carol {age:35})
(Carol {age:35}) -[:KNOWS]-> (Dave {age:28})
(Dave {age:28}) -[:KNOWS]-> (Eve {age:22})
(Alice {age:30}) -[:FRIENDS]-> (Carol {age:35})
The relationship query asks only for KNOWS edges, so the single
FRIENDS edge is filtered out by the pattern. The WHERE query keeps
only people older than 25. Finally a CREATE adds a Guest node named
Frank in its own transaction, and the example confirms the new label is
registered in the graph.
How to run
go run ./examples/22_cypher
Expected output
MATCH (n:Person) RETURN n.name AS name ORDER BY name
Alice
Bob
Carol
Dave
Eve
MATCH (n:Person) WHERE n.age > 25 RETURN n.name AS name, n.age AS age ORDER BY name
Alice age 30
Carol age 35
Dave age 28
MATCH (a:Person)-[:KNOWS]->(b:Person) RETURN a.name AS from, b.name AS to ORDER BY from, to
Alice KNOWS Bob
Bob KNOWS Carol
Carol KNOWS Dave
Dave KNOWS Eve
CREATE (n:Guest {name: "Frank"})
created Guest{name: "Frank"} — label registered in graph
Every query that can return more than one row carries an ORDER BY, so
the output is byte-stable and pinned by example_test.go.
Cypher clauses exercised
MATCH (n:Person)— a label scan over thePersonnodes.RETURN n.name AS name— projection of a node property under an alias.ORDER BY name— deterministic ascending ordering of the result rows.WHERE n.age > $min— predicate filtering, with the threshold passed as a query parameter.MATCH (a:Person)-[:KNOWS]->(b:Person)— a directed relationship pattern restricted to theKNOWStype.CREATE (n:Guest {name: "Frank"})— a write transaction adding a labelled node with an inline property map.
Key APIs
graph/lpg.New/Graph.AddNode/SetNodeLabel/SetNodeProperty/AddEdge/SetEdgeLabel— build the labelled property graph.cypher.NewEngine— bind the graph to a query engine.cypher.Engine.Run— execute a read query (the threeMATCHqueries).cypher.Engine.RunInTx— execute a write query (CREATE) atomically.cypher.Result— forward-only streaming result set (Next,Record,Err,Close).cypher/expr.StringValue/expr.IntegerValue— the runtime value types the engine returns for projectedstringand integer properties; the example unwraps them to bare Gostring/int64for printing.
Further reading
cypher— the Cypher engine package documentationcypher/expr— the runtime value model returned in result recordsgraph/lpg— the labelled property graph used as the query surface- Example 24 — social network CLI — an interactive CLI running Cypher over a persistent LPG
- Example 25 — software house API — a REST API serving Cypher queries
- docs/cypher.md — the Cypher engine design note
- docs/examples-standard.md — the standard every example follows
Documentation
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Overview ¶
Example 22_cypher — the GoGraph Cypher engine, the module's flagship (100% openCypher TCK compliant at the execution level).
It builds a small social graph with the property-graph API and then queries it with five Cypher idioms: a label scan with projection and ORDER BY, a WHERE filter, a relationship pattern, and a CREATE inside a write transaction. Every value is read back from the result record and printed in human-readable form — names and ages, never raw node IDs.
Every query that can return more than one row carries an ORDER BY, so the output is fully deterministic for the hard-coded inputs and serves as the regression baseline a future change should preserve. Run `go run ./examples/22_cypher` to capture the stdout.
Source Files