graph/db: implement SQLStore.LookupAlias

In this commit, we let the SQLStore implement LookupAlias. This then
lets us run the TestAliasLookup unit test against the SQL backends.

graph/db/graph_test.go

@@ -325,10 +325,11 @@ func TestPartialNode(t *testing.T) {
 	require.ErrorIs(t, err, ErrGraphNodeNotFound)
 }
 
+// TestAliasLookup tests the alias lookup functionality of the graph store.
 func TestAliasLookup(t *testing.T) {
 	t.Parallel()
 
-	graph := MakeTestGraph(t)
+	graph := MakeTestGraphNew(t)
 
 	// We'd like to test the alias index within the database, so first
 	// create a new test node.
@@ -336,9 +337,7 @@ func TestAliasLookup(t *testing.T) {
 
 	// Add the node to the graph's database, this should also insert an
 	// entry into the alias index for this node.
-	if err := graph.AddLightningNode(testNode); err != nil {
-		t.Fatalf("unable to add node: %v", err)
-	}
+	require.NoError(t, graph.AddLightningNode(testNode))
 
 	// Next, attempt to lookup the alias. The alias should exactly match
 	// the one which the test node was assigned.
@@ -346,10 +345,7 @@ func TestAliasLookup(t *testing.T) {
 	require.NoError(t, err, "unable to generate pubkey")
 	dbAlias, err := graph.LookupAlias(nodePub)
 	require.NoError(t, err, "unable to find alias")
-	if dbAlias != testNode.Alias {
-		t.Fatalf("aliases don't match, expected %v got %v",
-			testNode.Alias, dbAlias)
-	}
+	require.Equal(t, testNode.Alias, dbAlias)
 
 	// Ensure that looking up a non-existent alias results in an error.
 	node := createTestVertex(t)

graph/db/sql_store.go

@@ -334,6 +334,43 @@ func (s *SQLStore) FetchNodeFeatures(nodePub route.Vertex) (
 	return fetchNodeFeatures(ctx, s.db, nodePub)
 }
 
+// LookupAlias attempts to return the alias as advertised by the target node.
+//
+// NOTE: part of the V1Store interface.
+func (s *SQLStore) LookupAlias(pub *btcec.PublicKey) (string, error) {
+	var (
+		ctx    = context.TODO()
+		readTx = NewReadTx()
+		alias  string
+	)
+	err := s.db.ExecTx(ctx, readTx, func(db SQLQueries) error {
+		dbNode, err := db.GetNodeByPubKey(
+			ctx, sqlc.GetNodeByPubKeyParams{
+				Version: int16(ProtocolV1),
+				PubKey:  pub.SerializeCompressed(),
+			},
+		)
+		if errors.Is(err, sql.ErrNoRows) {
+			return ErrNodeAliasNotFound
+		} else if err != nil {
+			return fmt.Errorf("unable to fetch node: %w", err)
+		}
+
+		if !dbNode.Alias.Valid {
+			return ErrNodeAliasNotFound
+		}
+
+		alias = dbNode.Alias.String
+
+		return nil
+	}, func() {})
+	if err != nil {
+		return "", fmt.Errorf("unable to look up alias: %w", err)
+	}
+
+	return alias, nil
+}
+
 // getNodeByPubKey attempts to look up a target node by its public key.
 func getNodeByPubKey(ctx context.Context, db SQLQueries,
 	pubKey route.Vertex) (int64, *models.LightningNode, error) {