From f371ee793cead3664398c6ee87091385767dff38 Mon Sep 17 00:00:00 2001
From: blankrain <731014656@qq.com>
Date: Thu, 5 Dec 2019 17:57:33 +0800
Subject: [PATCH] for 
 https://discuss.dgraph.io/t/performance-is-not-good-when-finding-the-paths-between-2-nodes-with-k-shortest/3533/2

---
 query/shortest.go | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/query/shortest.go b/query/shortest.go
index d8de9339c59..f738f2d7f11 100644
--- a/query/shortest.go
+++ b/query/shortest.go
@@ -202,6 +202,9 @@ func (sg *SubGraph) expandOut(ctx context.Context,
 							rch <- err
 							return
 						}
+						if canSkipRing(adjacencyMap, toUID, fromUID) {
+							continue
+						}
 						adjacencyMap[fromUID][toUID] = mapItem{
 							cost:  cost,
 							facet: facet,
@@ -686,3 +689,12 @@ func createkroutesubgraph(ctx context.Context, kroutes []route) []*SubGraph {
 	}
 	return res
 }
+
+func canSkipRing(adjacencyMap map[uint64]map[uint64]mapItem, k, v uint64) bool {
+	if adjacencyMap[k] != nil {
+		if _, ok := adjacencyMap[k][v]; ok {
+			return true
+		}
+	}
+	return false
+}