refactor: move graph related DB code to graph/db from channeldb

This is a pure refactor commit. It moves over all the graph related CRUD
code from `channeldb` to `graph/db`.

routing/bandwidth.go

@@ -3,8 +3,8 @@ package routing
 import (
 	"fmt"
 
-	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/fn"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
@@ -96,7 +96,7 @@ func newBandwidthManager(graph Graph, sourceNode route.Vertex,
 	// First, we'll collect the set of outbound edges from the target
 	// source node and add them to our bandwidth manager's map of channels.
 	err := graph.ForEachNodeChannel(sourceNode,
-		func(channel *channeldb.DirectedChannel) error {
+		func(channel *graphdb.DirectedChannel) error {
 			shortID := lnwire.NewShortChanIDFromInt(
 				channel.ChannelID,
 			)

routing/chainview/bitcoind.go

@@ -13,7 +13,7 @@ import (
 	"github.com/btcsuite/btcwallet/chain"
 	"github.com/btcsuite/btcwallet/wtxmgr"
 	"github.com/lightningnetwork/lnd/blockcache"
-	"github.com/lightningnetwork/lnd/channeldb"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 )
 
 // BitcoindFilteredChainView is an implementation of the FilteredChainView
@@ -448,7 +448,7 @@ func (b *BitcoindFilteredChainView) chainFilterer() {
 // rewound to ensure all relevant notifications are dispatched.
 //
 // NOTE: This is part of the FilteredChainView interface.
-func (b *BitcoindFilteredChainView) UpdateFilter(ops []channeldb.EdgePoint,
+func (b *BitcoindFilteredChainView) UpdateFilter(ops []graphdb.EdgePoint,
 	updateHeight uint32) error {
 
 	newUtxos := make([]wire.OutPoint, len(ops))

routing/chainview/btcd.go

@@ -13,7 +13,7 @@ import (
 	"github.com/btcsuite/btcd/rpcclient"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/blockcache"
-	"github.com/lightningnetwork/lnd/channeldb"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 )
 
 // BtcdFilteredChainView is an implementation of the FilteredChainView
@@ -456,7 +456,7 @@ type filterUpdate struct {
 // rewound to ensure all relevant notifications are dispatched.
 //
 // NOTE: This is part of the FilteredChainView interface.
-func (b *BtcdFilteredChainView) UpdateFilter(ops []channeldb.EdgePoint,
+func (b *BtcdFilteredChainView) UpdateFilter(ops []graphdb.EdgePoint,
 	updateHeight uint32) error {
 
 	newUtxos := make([]wire.OutPoint, len(ops))

routing/chainview/interface.go

@@ -3,7 +3,7 @@ package chainview
 import (
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/wire"
-	"github.com/lightningnetwork/lnd/channeldb"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 )
 
 // FilteredChainView represents a subscription to a certain subset of the
@@ -43,7 +43,7 @@ type FilteredChainView interface {
 	// relevant notifications are dispatched, meaning blocks with a height
 	// lower than the best known height might be sent over the
 	// FilteredBlocks() channel.
-	UpdateFilter(ops []channeldb.EdgePoint, updateHeight uint32) error
+	UpdateFilter(ops []graphdb.EdgePoint, updateHeight uint32) error
 
 	// FilterBlock takes a block hash, and returns a FilteredBlocks which
 	// is the result of applying the current registered UTXO sub-set on the

routing/chainview/interface_test.go

@@ -21,7 +21,7 @@ import (
 	_ "github.com/btcsuite/btcwallet/walletdb/bdb" // Required to register the boltdb walletdb implementation.
 	"github.com/lightninglabs/neutrino"
 	"github.com/lightningnetwork/lnd/blockcache"
-	"github.com/lightningnetwork/lnd/channeldb"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/kvdb"
 	"github.com/lightningnetwork/lnd/lntest/unittest"
 	"github.com/lightningnetwork/lnd/lntest/wait"
@@ -218,7 +218,7 @@ func testFilterBlockNotifications(node *rpctest.Harness,
 	require.NoError(t, err, "unable to get current height")
 
 	// Now we'll add both outpoints to the current filter.
-	filter := []channeldb.EdgePoint{
+	filter := []graphdb.EdgePoint{
 		{FundingPkScript: targetScript, OutPoint: *outPoint1},
 		{FundingPkScript: targetScript, OutPoint: *outPoint2},
 	}
@@ -328,7 +328,7 @@ func testUpdateFilterBackTrack(node *rpctest.Harness,
 
 	// After the block has been mined+notified we'll update the filter with
 	// a _prior_ height so a "rewind" occurs.
-	filter := []channeldb.EdgePoint{
+	filter := []graphdb.EdgePoint{
 		{FundingPkScript: testScript, OutPoint: *outPoint},
 	}
 	err = chainView.UpdateFilter(filter, uint32(currentHeight))
@@ -417,7 +417,7 @@ func testFilterSingleBlock(node *rpctest.Harness, chainView FilteredChainView,
 
 	// Now we'll manually trigger filtering the block generated above.
 	// First, we'll add the two outpoints to our filter.
-	filter := []channeldb.EdgePoint{
+	filter := []graphdb.EdgePoint{
 		{FundingPkScript: testScript, OutPoint: *outPoint1},
 		{FundingPkScript: testScript, OutPoint: *outPoint2},
 	}

routing/chainview/neutrino.go

@@ -12,7 +12,7 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightninglabs/neutrino"
 	"github.com/lightningnetwork/lnd/blockcache"
-	"github.com/lightningnetwork/lnd/channeldb"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/lntypes"
 )
 
@@ -320,7 +320,7 @@ func (c *CfFilteredChainView) FilterBlock(blockHash *chainhash.Hash) (*FilteredB
 // rewound to ensure all relevant notifications are dispatched.
 //
 // NOTE: This is part of the FilteredChainView interface.
-func (c *CfFilteredChainView) UpdateFilter(ops []channeldb.EdgePoint,
+func (c *CfFilteredChainView) UpdateFilter(ops []graphdb.EdgePoint,
 	updateHeight uint32) error {
 
 	log.Tracef("Updating chain filter with new UTXO's: %v", ops)

routing/graph.go

@@ -4,7 +4,7 @@ import (
 	"fmt"
 
 	"github.com/btcsuite/btcd/btcutil"
-	"github.com/lightningnetwork/lnd/channeldb"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
 )
@@ -15,7 +15,7 @@ type Graph interface {
 	// ForEachNodeChannel calls the callback for every channel of the given
 	// node.
 	ForEachNodeChannel(nodePub route.Vertex,
-		cb func(channel *channeldb.DirectedChannel) error) error
+		cb func(channel *graphdb.DirectedChannel) error) error
 
 	// FetchNodeFeatures returns the features of the given node.
 	FetchNodeFeatures(nodePub route.Vertex) (*lnwire.FeatureVector, error)

routing/integrated_routing_context_test.go

@@ -7,8 +7,8 @@ import (
 	"testing"
 	"time"
 
-	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/fn"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/kvdb"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
@@ -338,11 +338,11 @@ var _ GraphSessionFactory = (*mockGraphSessionFactory)(nil)
 var _ Graph = (*mockGraphSessionFactory)(nil)
 
 type mockGraphSessionFactoryChanDB struct {
-	graph *channeldb.ChannelGraph
+	graph *graphdb.ChannelGraph
 }
 
 func newMockGraphSessionFactoryFromChanDB(
-	graph *channeldb.ChannelGraph) *mockGraphSessionFactoryChanDB {
+	graph *graphdb.ChannelGraph) *mockGraphSessionFactoryChanDB {
 
 	return &mockGraphSessionFactoryChanDB{
 		graph: graph,
@@ -368,11 +368,11 @@ func (g *mockGraphSessionFactoryChanDB) NewGraphSession() (Graph, func() error,
 var _ GraphSessionFactory = (*mockGraphSessionFactoryChanDB)(nil)
 
 type mockGraphSessionChanDB struct {
-	graph *channeldb.ChannelGraph
+	graph *graphdb.ChannelGraph
 	tx    kvdb.RTx
 }
 
-func newMockGraphSessionChanDB(graph *channeldb.ChannelGraph) Graph {
+func newMockGraphSessionChanDB(graph *graphdb.ChannelGraph) Graph {
 	return &mockGraphSessionChanDB{
 		graph: graph,
 	}
@@ -392,7 +392,7 @@ func (g *mockGraphSessionChanDB) close() error {
 }
 
 func (g *mockGraphSessionChanDB) ForEachNodeChannel(nodePub route.Vertex,
-	cb func(channel *channeldb.DirectedChannel) error) error {
+	cb func(channel *graphdb.DirectedChannel) error) error {
 
 	return g.graph.ForEachNodeDirectedChannel(g.tx, nodePub, cb)
 }

routing/mock_graph_test.go

@@ -7,7 +7,7 @@ import (
 
 	"github.com/btcsuite/btcd/btcec/v2"
 	"github.com/btcsuite/btcd/btcutil"
-	"github.com/lightningnetwork/lnd/channeldb"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/graph/db/models"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
@@ -166,12 +166,12 @@ func (m *mockGraph) addChannel(id uint64, node1id, node2id byte,
 //
 // NOTE: Part of the Graph interface.
 func (m *mockGraph) ForEachNodeChannel(nodePub route.Vertex,
-	cb func(channel *channeldb.DirectedChannel) error) error {
+	cb func(channel *graphdb.DirectedChannel) error) error {
 
 	// Look up the mock node.
 	node, ok := m.nodes[nodePub]
 	if !ok {
-		return channeldb.ErrGraphNodeNotFound
+		return graphdb.ErrGraphNodeNotFound
 	}
 
 	// Iterate over all of its channels.
@@ -188,7 +188,7 @@ func (m *mockGraph) ForEachNodeChannel(nodePub route.Vertex,
 
 		// Call the per channel callback.
 		err := cb(
-			&channeldb.DirectedChannel{
+			&graphdb.DirectedChannel{
 				ChannelID:    channel.id,
 				IsNode1:      nodePub == node1,
 				OtherNode:    peer,

routing/pathfind.go

@@ -11,9 +11,9 @@ import (
 
 	"github.com/btcsuite/btcd/btcutil"
 	sphinx "github.com/lightningnetwork/lightning-onion"
-	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/feature"
 	"github.com/lightningnetwork/lnd/fn"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/graph/db/models"
 	"github.com/lightningnetwork/lnd/lnutils"
 	"github.com/lightningnetwork/lnd/lnwire"
@@ -496,7 +496,7 @@ func getOutgoingBalance(node route.Vertex, outgoingChans map[uint64]struct{},
 	g Graph) (lnwire.MilliSatoshi, lnwire.MilliSatoshi, error) {
 
 	var max, total lnwire.MilliSatoshi
-	cb := func(channel *channeldb.DirectedChannel) error {
+	cb := func(channel *graphdb.DirectedChannel) error {
 		if !channel.OutPolicySet {
 			return nil
 		}
@@ -1299,7 +1299,7 @@ func processNodeForBlindedPath(g Graph, node route.Vertex,
 	// Now, iterate over the node's channels in search for paths to this
 	// node that can be used for blinded paths
 	err = g.ForEachNodeChannel(node,
-		func(channel *channeldb.DirectedChannel) error {
+		func(channel *graphdb.DirectedChannel) error {
 			// Keep track of how many incoming channels this node
 			// has. We only use a node as an introduction node if it
 			// has channels other than the one that lead us to it.

routing/pathfind_test.go

@@ -23,6 +23,7 @@ import (
 	sphinx "github.com/lightningnetwork/lightning-onion"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/fn"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/graph/db/models"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	switchhop "github.com/lightningnetwork/lnd/htlcswitch/hop"
@@ -155,7 +156,7 @@ type testChan struct {
 
 // makeTestGraph creates a new instance of a channeldb.ChannelGraph for testing
 // purposes.
-func makeTestGraph(t *testing.T, useCache bool) (*channeldb.ChannelGraph,
+func makeTestGraph(t *testing.T, useCache bool) (*graphdb.ChannelGraph,
 	kvdb.Backend, error) {
 
 	// Create channelgraph for the first time.
@@ -167,7 +168,7 @@ func makeTestGraph(t *testing.T, useCache bool) (*channeldb.ChannelGraph,
 	t.Cleanup(backendCleanup)
 
 	opts := channeldb.DefaultOptions()
-	graph, err := channeldb.NewChannelGraph(
+	graph, err := graphdb.NewChannelGraph(
 		backend, opts.RejectCacheSize, opts.ChannelCacheSize,
 		opts.BatchCommitInterval, opts.PreAllocCacheNumNodes,
 		useCache, false,
@@ -217,7 +218,7 @@ func parseTestGraph(t *testing.T, useCache bool, path string) (
 	privKeyMap := make(map[string]*btcec.PrivateKey)
 	channelIDs := make(map[route.Vertex]map[route.Vertex]uint64)
 	links := make(map[lnwire.ShortChannelID]htlcswitch.ChannelLink)
-	var source *channeldb.LightningNode
+	var source *graphdb.LightningNode
 
 	// First we insert all the nodes within the graph as vertexes.
 	for _, node := range g.Nodes {
@@ -226,7 +227,7 @@ func parseTestGraph(t *testing.T, useCache bool, path string) (
 			return nil, err
 		}
 
-		dbNode := &channeldb.LightningNode{
+		dbNode := &graphdb.LightningNode{
 			HaveNodeAnnouncement: true,
 			AuthSigBytes:         testSig.Serialize(),
 			LastUpdate:           testTime,
@@ -357,7 +358,7 @@ func parseTestGraph(t *testing.T, useCache bool, path string) (
 		}
 
 		err = graph.AddChannelEdge(&edgeInfo)
-		if err != nil && err != channeldb.ErrEdgeAlreadyExist {
+		if err != nil && err != graphdb.ErrEdgeAlreadyExist {
 			return nil, err
 		}
 
@@ -477,7 +478,7 @@ type testChannel struct {
 }
 
 type testGraphInstance struct {
-	graph        *channeldb.ChannelGraph
+	graph        *graphdb.ChannelGraph
 	graphBackend kvdb.Backend
 
 	// aliasMap is a map from a node's alias to its public key. This type is
@@ -539,7 +540,7 @@ func createTestGraphFromChannels(t *testing.T, useCache bool,
 
 	nodeIndex := byte(0)
 	addNodeWithAlias := func(alias string, features *lnwire.FeatureVector) (
-		*channeldb.LightningNode, error) {
+		*graphdb.LightningNode, error) {
 
 		keyBytes := []byte{
 			0, 0, 0, 0, 0, 0, 0, 0,
@@ -554,7 +555,7 @@ func createTestGraphFromChannels(t *testing.T, useCache bool,
 			features = lnwire.EmptyFeatureVector()
 		}
 
-		dbNode := &channeldb.LightningNode{
+		dbNode := &graphdb.LightningNode{
 			HaveNodeAnnouncement: true,
 			AuthSigBytes:         testSig.Serialize(),
 			LastUpdate:           testTime,
@@ -665,7 +666,7 @@ func createTestGraphFromChannels(t *testing.T, useCache bool,
 		}
 
 		err = graph.AddChannelEdge(&edgeInfo)
-		if err != nil && err != channeldb.ErrEdgeAlreadyExist {
+		if err != nil && err != graphdb.ErrEdgeAlreadyExist {
 			return nil, err
 		}
 
@@ -1210,7 +1211,7 @@ func runPathFindingWithAdditionalEdges(t *testing.T, useCache bool) {
 	dogePubKey, err := btcec.ParsePubKey(dogePubKeyBytes)
 	require.NoError(t, err, "unable to parse public key from bytes")
 
-	doge := &channeldb.LightningNode{}
+	doge := &graphdb.LightningNode{}
 	doge.AddPubKey(dogePubKey)
 	doge.Alias = "doge"
 	copy(doge.PubKeyBytes[:], dogePubKeyBytes)
@@ -3026,7 +3027,7 @@ func runInboundFees(t *testing.T, useCache bool) {
 
 type pathFindingTestContext struct {
 	t                 *testing.T
-	graph             *channeldb.ChannelGraph
+	graph             *graphdb.ChannelGraph
 	restrictParams    RestrictParams
 	bandwidthHints    bandwidthHints
 	pathFindingConfig PathFindingConfig
@@ -3108,7 +3109,7 @@ func (c *pathFindingTestContext) assertPath(path []*unifiedEdge,
 
 // dbFindPath calls findPath after getting a db transaction from the database
 // graph.
-func dbFindPath(graph *channeldb.ChannelGraph,
+func dbFindPath(graph *graphdb.ChannelGraph,
 	additionalEdges map[route.Vertex][]AdditionalEdge,
 	bandwidthHints bandwidthHints,
 	r *RestrictParams, cfg *PathFindingConfig,
@@ -3148,7 +3149,7 @@ func dbFindPath(graph *channeldb.ChannelGraph,
 
 // dbFindBlindedPaths calls findBlindedPaths after getting a db transaction from
 // the database graph.
-func dbFindBlindedPaths(graph *channeldb.ChannelGraph,
+func dbFindBlindedPaths(graph *graphdb.ChannelGraph,
 	restrictions *blindedPathRestrictions) ([][]blindedHop, error) {
 
 	sourceNode, err := graph.SourceNode()

routing/payment_session_source.go

@@ -2,8 +2,8 @@ package routing
 
 import (
 	"github.com/btcsuite/btcd/btcec/v2"
-	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/fn"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/graph/db/models"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
@@ -24,7 +24,7 @@ type SessionSource struct {
 	GraphSessionFactory GraphSessionFactory
 
 	// SourceNode is the graph's source node.
-	SourceNode *channeldb.LightningNode
+	SourceNode *graphdb.LightningNode
 
 	// GetLink is a method that allows querying the lower link layer
 	// to determine the up to date available bandwidth at a prospective link
@@ -101,7 +101,7 @@ func RouteHintsToEdges(routeHints [][]zpay32.HopHint, target route.Vertex) (
 			// we'll need to look at the next hint's start node. If
 			// we've reached the end of the hints list, we can
 			// assume we've reached the destination.
-			endNode := &channeldb.LightningNode{}
+			endNode := &graphdb.LightningNode{}
 			if i != len(routeHint)-1 {
 				endNode.AddPubKey(routeHint[i+1].NodeID)
 			} else {

routing/payment_session_test.go

@@ -4,7 +4,7 @@ import (
 	"testing"
 	"time"
 
-	"github.com/lightningnetwork/lnd/channeldb"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/graph/db/models"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwire"
@@ -89,7 +89,7 @@ func TestUpdateAdditionalEdge(t *testing.T) {
 
 	// Create a minimal test node using the private key priv1.
 	pub := priv1.PubKey().SerializeCompressed()
-	testNode := &channeldb.LightningNode{}
+	testNode := &graphdb.LightningNode{}
 	copy(testNode.PubKeyBytes[:], pub)
 
 	nodeID, err := testNode.PubKey()

routing/router_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/lightningnetwork/lnd/clock"
 	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/graph"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/graph/db/models"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/input"
@@ -68,7 +69,7 @@ type testCtx struct {
 
 	graphBuilder *mockGraphBuilder
 
-	graph *channeldb.ChannelGraph
+	graph *graphdb.ChannelGraph
 
 	aliases map[string]route.Vertex
 
@@ -191,7 +192,7 @@ func createTestCtxFromGraphInstanceAssumeValid(t *testing.T,
 	return ctx
 }
 
-func createTestNode() (*channeldb.LightningNode, error) {
+func createTestNode() (*graphdb.LightningNode, error) {
 	updateTime := rand.Int63()
 
 	priv, err := btcec.NewPrivateKey()
@@ -200,7 +201,7 @@ func createTestNode() (*channeldb.LightningNode, error) {
 	}
 
 	pub := priv.PubKey().SerializeCompressed()
-	n := &channeldb.LightningNode{
+	n := &graphdb.LightningNode{
 		HaveNodeAnnouncement: true,
 		LastUpdate:           time.Unix(updateTime, 0),
 		Addresses:            testAddrs,
@@ -2898,7 +2899,7 @@ func TestAddEdgeUnknownVertexes(t *testing.T) {
 
 	// Now check that we can update the node info for the partial node
 	// without messing up the channel graph.
-	n1 := &channeldb.LightningNode{
+	n1 := &graphdb.LightningNode{
 		HaveNodeAnnouncement: true,
 		LastUpdate:           time.Unix(123, 0),
 		Addresses:            testAddrs,
@@ -2911,7 +2912,7 @@ func TestAddEdgeUnknownVertexes(t *testing.T) {
 
 	require.NoError(t, ctx.graph.AddLightningNode(n1))
 
-	n2 := &channeldb.LightningNode{
+	n2 := &graphdb.LightningNode{
 		HaveNodeAnnouncement: true,
 		LastUpdate:           time.Unix(123, 0),
 		Addresses:            testAddrs,

routing/unified_edges.go

@@ -4,7 +4,7 @@ import (
 	"math"
 
 	"github.com/btcsuite/btcd/btcutil"
-	"github.com/lightningnetwork/lnd/channeldb"
+	graphdb "github.com/lightningnetwork/lnd/graph/db"
 	"github.com/lightningnetwork/lnd/graph/db/models"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwire"
@@ -95,7 +95,7 @@ func (u *nodeEdgeUnifier) addPolicy(fromNode route.Vertex,
 // addGraphPolicies adds all policies that are known for the toNode in the
 // graph.
 func (u *nodeEdgeUnifier) addGraphPolicies(g Graph) error {
-	cb := func(channel *channeldb.DirectedChannel) error {
+	cb := func(channel *graphdb.DirectedChannel) error {
 		// If there is no edge policy for this candidate node, skip.
 		// Note that we are searching backwards so this node would have
 		// come prior to the pivot node in the route.