Support k shortest paths

Author: ashwin95r

gql/parser_test.go

@@ -906,7 +906,7 @@ func TestParseQueryWithMultipleVar(t *testing.T) {
 func TestParseShortestPath(t *testing.T) {
 	query := `
 	{
-		shortest(from:0x0a, to:0x0b) {
+		shortest(from:0x0a, to:0x0b, numpaths: 3) {
 			friends
 			name
 		}
@@ -918,6 +918,7 @@ func TestParseShortestPath(t *testing.T) {
 	require.Equal(t, 1, len(res.Query))
 	require.Equal(t, "0x0a", res.Query[0].Args["from"])
 	require.Equal(t, "0x0b", res.Query[0].Args["to"])
+	require.Equal(t, "3", res.Query[0].Args["numpaths"])
 }
 
 func TestParseMultipleQueries(t *testing.T) {

query/query.go

@@ -145,6 +145,7 @@ type params struct {
 	isGroupBy    bool
 	groupbyAttrs []gql.AttrLang
 	uidCount     string
+	numPaths     int
 }
 
 // SubGraph is the way to represent data internally. It contains both the
@@ -739,6 +740,13 @@ func (args *params) fill(gq *gql.GraphQuery) error {
 		}
 		args.RecurseDepth = from
 	}
+	if v, ok := gq.Args["numpaths"]; ok && args.Alias == "shortest" {
+		numPaths, err := strconv.ParseUint(v, 0, 64)
+		if err != nil {
+			return err
+		}
+		args.numPaths = int(numPaths)
+	}
 	if v, ok := gq.Args["from"]; ok && args.Alias == "shortest" {
 		from, err := strconv.ParseUint(v, 0, 64)
 		if err != nil {
@@ -1897,7 +1905,7 @@ func (sg *SubGraph) sortAndPaginateUsingVar(ctx context.Context) error {
 // isValidArg checks if arg passed is valid keyword.
 func isValidArg(a string) bool {
 	switch a {
-	case "from", "to", "orderasc", "orderdesc", "first", "offset", "after", "depth":
+	case "numpaths", "from", "to", "orderasc", "orderdesc", "first", "offset", "after", "depth":
 		return true
 	}
 	return false
@@ -2088,7 +2096,7 @@ func (req *QueryRequest) ProcessQuery(ctx context.Context) error {
 		return true
 	}
 
-	var shortestSg *SubGraph
+	var shortestSg []*SubGraph
 	for i := 0; i < len(req.Subgraphs) && numQueriesDone < len(req.Subgraphs); i++ {
 		errChan := make(chan error, len(req.Subgraphs))
 		var idxList []int
@@ -2165,8 +2173,8 @@ func (req *QueryRequest) ProcessQuery(ctx context.Context) error {
 	req.Latency.Processing += time.Since(execStart)
 
 	// If we had a shortestPath SG, append it to the result.
-	if shortestSg != nil {
-		req.Subgraphs = append(req.Subgraphs, shortestSg)
+	if len(shortestSg) != 0 {
+		req.Subgraphs = append(req.Subgraphs, shortestSg...)
 	}
 	return nil
 }

query/query_test.go

@@ -1629,6 +1629,53 @@ func TestShortestPath_NoPath(t *testing.T) {
 		js)
 }
 
+func TestKShortestPathWeighted(t *testing.T) {
+	populateGraph(t)
+	query := `
+		{
+			shortest(from: 1, to:1001, numpaths: 4) {
+				path @facets(weight)
+			}
+		}`
+	// We only get one path in this case as the facet is present only in one path.
+	js := processToFastJSON(t, query)
+	require.JSONEq(t,
+		`{"_path_":[{"_uid_":"0x1","path":[{"@facets":{"_":{"weight":0.100000}},"_uid_":"0x1f","path":[{"@facets":{"_":{"weight":0.100000}},"_uid_":"0x3e8","path":[{"@facets":{"_":{"weight":0.100000}},"_uid_":"0x3e9"}]}]}]}]}`,
+		js)
+}
+
+func TestKShortestPathWeighted1(t *testing.T) {
+	populateGraph(t)
+	query := `
+		{
+			shortest(from: 1, to:1003, numpaths: 3) {
+				path @facets(weight)
+			}
+		}`
+	js := processToFastJSON(t, query)
+	require.JSONEq(t,
+		`{"_path_":[{"_uid_":"0x1","path":[{"@facets":{"_":{"weight":0.100000}},"_uid_":"0x1f","path":[{"@facets":{"_":{"weight":0.100000}},"_uid_":"0x3e8","path":[{"@facets":{"_":{"weight":0.100000}},"_uid_":"0x3e9","path":[{"@facets":{"_":{"weight":0.100000}},"_uid_":"0x3ea","path":[{"@facets":{"_":{"weight":0.600000}},"_uid_":"0x3eb"}]}]}]}]}]},{"_uid_":"0x1","path":[{"@facets":{"_":{"weight":0.100000}},"_uid_":"0x1f","path":[{"@facets":{"_":{"weight":0.100000}},"_uid_":"0x3e8","path":[{"@facets":{"_":{"weight":0.700000}},"_uid_":"0x3ea","path":[{"@facets":{"_":{"weight":0.600000}},"_uid_":"0x3eb"}]}]}]}]},{"_uid_":"0x1","path":[{"@facets":{"_":{"weight":0.100000}},"_uid_":"0x1f","path":[{"@facets":{"_":{"weight":0.100000}},"_uid_":"0x3e8","path":[{"@facets":{"_":{"weight":0.100000}},"_uid_":"0x3e9","path":[{"@facets":{"_":{"weight":1.500000}},"_uid_":"0x3eb"}]}]}]}]}]}`,
+		js)
+}
+
+func TestTwoShortestPath(t *testing.T) {
+	populateGraph(t)
+	query := `
+		{
+			A as shortest(from: 1, to:1002, numpaths: 2) {
+				path
+			}
+
+			me(id: var( A)) {
+				name
+			}
+		}`
+	js := processToFastJSON(t, query)
+	require.JSONEq(t,
+		`{"_path_":[{"_uid_":"0x1","path":[{"_uid_":"0x1f","path":[{"_uid_":"0x3e8","path":[{"_uid_":"0x3ea"}]}]}]},{"_uid_":"0x1","path":[{"_uid_":"0x1f","path":[{"_uid_":"0x3e8","path":[{"_uid_":"0x3e9","path":[{"_uid_":"0x3ea"}]}]}]}]}],"me":[{"name":"Michonne"},{"name":"Andrea"},{"name":"Alice"},{"name":"Matt"}]}`,
+		js)
+}
+
 func TestShortestPath(t *testing.T) {
 	populateGraph(t)
 	query := `