fix(GraphQL): Link xids properly if there are duplicate xids within the same add request.

graphql/resolve/add_mutation_test.yaml

@@ -2216,8 +2216,8 @@
 
 - name: "Deep mutation three level xid"
   gqlmutation: |
-    mutation($auth: AddPost1Input!) {
-      addPost1(input: [$auth]) {
+    mutation($auth: [AddPost1Input!]!) {
+      addPost1(input: $auth) {
         post1 {
           id
           comments {
@@ -2232,15 +2232,24 @@
 
   gqlvariables: |
     {
-      "auth": {
+      "auth": [{
         "id": "post1",
         "comments": [{
           "id": "comment1",
           "replies": [{
             "id": "reply1"
           }]
         }]
-      }
+      },
+      {
+        "id": "post2",
+        "comments": [{
+          "id": "comment2",
+          "replies": [{
+            "id": "reply1"
+          }]
+        }]
+      }]
     }
   dgquery: |-
     query {
@@ -2250,8 +2259,12 @@
       Comment16 as Comment16(func: eq(Comment1.id, "reply1")) @filter(type(Comment1)) {
         uid
       }
+      Comment110 as Comment110(func: eq(Comment1.id, "comment2")) @filter(type(Comment1)) {
+        uid
+      }
     }
   dgmutations:
+    # Create comment1 if it doesn't exist.
     - setjson: |
         {
           "Comment1.id": "comment1",
@@ -2261,6 +2274,7 @@
           "uid": "_:Comment14"
         }
       cond: "@if(eq(len(Comment14), 0))"
+    # Create reply1 if it doesn't exist.
     - setjson: |
         {
           "Comment1.id": "reply1",
@@ -2270,15 +2284,41 @@
           "uid": "_:Comment16"
         }
       cond: "@if(eq(len(Comment16), 0) AND eq(len(Comment14), 0))"
+    # Link comment1 and reply1 if reply exists but comment doesn't.
     - setjson: |
         {"uid":"_:Comment14", "Comment1.replies": [{"uid": "uid(Comment16)"}]}
       cond: "@if(eq(len(Comment16), 1) AND eq(len(Comment14), 0))"
+    # Link comment1 and reply1 if both don't exist.
     - setjson: |
         {"uid":"_:Comment14", "Comment1.replies": [{"uid": "_:Comment16"}]}
       cond: "@if(eq(len(Comment16), 0) AND eq(len(Comment14), 0))"
+    # useless mutation which needs investigation
     - setjson: |
         {"uid":"uid(Comment16)"}
       cond: "@if(eq(len(Comment16), 1) AND eq(len(Comment14), 0))"
+    # create comment2 if it doesn't exist
+    - setjson: |
+        {
+          "Comment1.id": "comment2",
+          "dgraph.type": [
+            "Comment1"
+          ],
+          "uid": "_:Comment110"
+        }
+      cond: "@if(eq(len(Comment110), 0))"
+    # Link comment1 and reply1 if reply exists but comment doesn't.
+    - setjson: |
+        {"uid":"_:Comment110", "Comment1.replies": [{"uid": "uid(Comment16)"}]}
+      cond: "@if(eq(len(Comment16), 1) AND eq(len(Comment110), 0))"
+    # Link comment2 and reply1 if both don't exist.
+    - setjson: |
+        {"uid":"_:Comment110", "Comment1.replies": [{"uid": "_:Comment16"}]}
+      cond: "@if(eq(len(Comment16), 0) AND eq(len(Comment110), 0))"
+    # useless mutation which needs investigation
+
+    - setjson: |
+        {"uid":"uid(Comment16)"}
+      cond: "@if(eq(len(Comment16), 1) AND eq(len(Comment110), 0))"
   dgquerysec: |-
     query {
       Post12 as Post12(func: eq(Post1.id, "post1")) @filter(type(Post1)) {
@@ -2287,6 +2327,12 @@
       Comment14 as Comment14(func: eq(Comment1.id, "comment1")) @filter(type(Comment1)) {
         uid
       }
+      Post18 as Post18(func: eq(Post1.id, "post2")) @filter(type(Post1)) {
+        uid
+      }
+      Comment110 as Comment110(func: eq(Comment1.id, "comment2")) @filter(type(Comment1)) {
+        uid
+      }
     }
   dgmutationssec:
     - setjson: |
@@ -2300,6 +2346,17 @@
           "uid":"_:Post12"
         }
       cond: "@if(eq(len(Post12), 0) AND eq(len(Comment14), 1))"
+    - setjson: |
+        {
+          "Post1.comments":
+            [{
+              "uid":"uid(Comment110)"
+            }],
+          "Post1.id":"post2",
+          "dgraph.type":["Post1"],
+          "uid":"_:Post18"
+        }
+      cond: "@if(eq(len(Post18), 0) AND eq(len(Comment110), 1))"
 
 -
   name: "Add mutation error on @id field for empty value"

graphql/resolve/mutation_rewriter.go

@@ -1065,7 +1065,15 @@ func rewriteObject(
 	newObj["uid"] = myUID
 	frag := newFragment(newObj)
 	frag.newNodes[variable] = typ
+
 	results := &mutationRes{secondPass: []*mutationFragment{frag}}
+	if xid != nil && !atTopLevel && !xidEncounteredFirstTime {
+		// If this is an xid that has been encountered before, e.g. think add mutations with
+		// multiple objects as input. In that case we don't need to add the fragment to create this
+		// object, so we clear it out. We do need other fragments for linking this node to its
+		// parent which are added later.
+		results.secondPass = results.secondPass[:0]
+	}
 
 	// if xidString != "", then we are adding with an xid.  In which case, we have to ensure
 	// as part of the upsert that the xid doesn't already exist.
@@ -1211,11 +1219,6 @@ func rewriteObject(
 		results.secondPass = appendFragments(results.secondPass, []*mutationFragment{xidFrag})
 	}
 
-	// if !xidEncounteredFirstTime, we have already seen the relevant fragments.
-	if xid != nil && !atTopLevel && !xidEncounteredFirstTime {
-		results.firstPass = []*mutationFragment{}
-	}
-
 	return results
 }