implement preliminary implementation of graph data model

pkg/neo4j/neo4j.go

@@ -39,6 +39,32 @@ type N struct {
 // Ensure N implements database.Database interface at compile time
 var _ database.Database = (*N)(nil)
 
+// CollectedResult wraps pre-fetched Neo4j records for iteration after session close
+// This is necessary because Neo4j results are lazy and need an open session for iteration
+type CollectedResult struct {
+	records []*neo4j.Record
+	index   int
+}
+
+// Next advances to the next record, returning true if there is one
+func (r *CollectedResult) Next(ctx context.Context) bool {
+	r.index++
+	return r.index < len(r.records)
+}
+
+// Record returns the current record
+func (r *CollectedResult) Record() *neo4j.Record {
+	if r.index < 0 || r.index >= len(r.records) {
+		return nil
+	}
+	return r.records[r.index]
+}
+
+// Len returns the number of records
+func (r *CollectedResult) Len() int {
+	return len(r.records)
+}
+
 // init registers the neo4j database factory
 func init() {
 	database.RegisterNeo4jFactory(func(
@@ -159,7 +185,8 @@ func (n *N) initNeo4jClient() error {
 
 
 // ExecuteRead executes a read query against Neo4j
-func (n *N) ExecuteRead(ctx context.Context, cypher string, params map[string]any) (neo4j.ResultWithContext, error) {
+// Returns a collected result that can be iterated after the session closes
+func (n *N) ExecuteRead(ctx context.Context, cypher string, params map[string]any) (*CollectedResult, error) {
 	session := n.driver.NewSession(ctx, neo4j.SessionConfig{AccessMode: neo4j.AccessModeRead})
 	defer session.Close(ctx)
 
@@ -168,7 +195,14 @@ func (n *N) ExecuteRead(ctx context.Context, cypher string, params map[string]an
 		return nil, fmt.Errorf("neo4j read query failed: %w", err)
 	}
 
-	return result, nil
+	// Collect all records before the session closes
+	// (Neo4j results are lazy and need an open session for iteration)
+	records, err := result.Collect(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("neo4j result collect failed: %w", err)
+	}
+
+	return &CollectedResult{records: records, index: -1}, nil
 }
 
 // ExecuteWrite executes a write query against Neo4j
@@ -217,7 +251,7 @@ func (n *N) Close() (err error) {
 	return
 }
 
-// Wipe removes all data
+// Wipe removes all data and re-applies schema
 func (n *N) Wipe() (err error) {
 	// Delete all nodes and relationships in Neo4j
 	ctx := context.Background()
@@ -226,9 +260,14 @@ func (n *N) Wipe() (err error) {
 		return fmt.Errorf("failed to wipe neo4j database: %w", err)
 	}
 
-	// Remove data directory
-	if err = os.RemoveAll(n.dataDir); chk.E(err) {
-		return
+	// Re-apply schema (indexes and constraints were deleted with the data)
+	if err = n.applySchema(ctx); err != nil {
+		return fmt.Errorf("failed to re-apply schema after wipe: %w", err)
+	}
+
+	// Re-initialize serial counter (it was deleted with the Marker node)
+	if err = n.initSerialCounter(); err != nil {
+		return fmt.Errorf("failed to re-init serial counter after wipe: %w", err)
 	}
 
 	return nil