graph/db: version ForEachNodeDirectedChannel and cacheable traversal

Add a gossip version parameter to ForEachNodeDirectedChannel on the
Store interface and both DB implementations (KVStore, SQLStore). The
NodeTraverser and routing.Graph interfaces remain unversioned since
pathfinding operates on the merged cross-version cache view.

The cache population in populateCache is updated in the same commit
because it is logically atomic with the versioning changes: the graph
cache is the unversioned, merged view used by pathfinding, so it must
be populated with data from all gossip versions. Without this change,
only v1 data would be loaded into the cache, making v2 nodes and
channels invisible to pathfinding.

graph/db/sql_store.go

@@ -988,13 +988,14 @@ func (s *SQLStore) ForEachNode(ctx context.Context,
 // Unknown policies are passed into the callback as nil values.
 //
 // NOTE: this is part of the graphdb.NodeTraverser interface.
-func (s *SQLStore) ForEachNodeDirectedChannel(nodePub route.Vertex,
-	cb func(channel *DirectedChannel) error, reset func()) error {
+func (s *SQLStore) ForEachNodeDirectedChannel(v lnwire.GossipVersion,
+	nodePub route.Vertex, cb func(channel *DirectedChannel) error,
+	reset func()) error {
 
 	var ctx = context.TODO()
 
 	return s.db.ExecTx(ctx, sqldb.ReadTxOpt(), func(db SQLQueries) error {
-		return forEachNodeDirectedChannel(ctx, db, nodePub, cb)
+		return forEachNodeDirectedChannel(ctx, db, v, nodePub, cb)
 	}, reset)
 }
 
@@ -3347,12 +3348,15 @@ func newSQLNodeTraverser(db SQLQueries,
 // node.
 //
 // NOTE: Part of the NodeTraverser interface.
-func (s *sqlNodeTraverser) ForEachNodeDirectedChannel(nodePub route.Vertex,
-	cb func(channel *DirectedChannel) error, _ func()) error {
+func (s *sqlNodeTraverser) ForEachNodeDirectedChannel(
+	nodePub route.Vertex, cb func(channel *DirectedChannel) error,
+	_ func()) error {
 
 	ctx := context.TODO()
 
-	return forEachNodeDirectedChannel(ctx, s.db, nodePub, cb)
+	return forEachNodeDirectedChannel(
+		ctx, s.db, lnwire.GossipVersion1, nodePub, cb,
+	)
 }
 
 // FetchNodeFeatures returns the features of the given node. If the node is
@@ -3372,7 +3376,8 @@ func (s *sqlNodeTraverser) FetchNodeFeatures(nodePub route.Vertex) (
 // channel and its incoming policy. If the node is not found, no error is
 // returned.
 func forEachNodeDirectedChannel(ctx context.Context, db SQLQueries,
-	nodePub route.Vertex, cb func(channel *DirectedChannel) error) error {
+	v lnwire.GossipVersion, nodePub route.Vertex,
+	cb func(channel *DirectedChannel) error) error {
 
 	toNodeCallback := func() route.Vertex {
 		return nodePub
@@ -3380,7 +3385,7 @@ func forEachNodeDirectedChannel(ctx context.Context, db SQLQueries,
 
 	dbID, err := db.GetNodeIDByPubKey(
 		ctx, sqlc.GetNodeIDByPubKeyParams{
-			Version: int16(lnwire.GossipVersion1),
+			Version: int16(v),
 			PubKey:  nodePub[:],
 		},
 	)
@@ -3392,7 +3397,7 @@ func forEachNodeDirectedChannel(ctx context.Context, db SQLQueries,
 
 	rows, err := db.ListChannelsByNodeID(
 		ctx, sqlc.ListChannelsByNodeIDParams{
-			Version: int16(lnwire.GossipVersion1),
+			Version: int16(v),
 			NodeID1: dbID,
 		},
 	)