perf(GraphQL): Part-1: Pagination for root user query is applied at r…

…oot auth query (GRAPHQL-854) (#7100)

This PR moves the pagination parameters for root user query to root auth query. This greatly optimizes the number of nodes that need to be processed by child auth queries.

graphql/resolve/auth_query_test.yaml

@@ -702,11 +702,11 @@
     USER: "user1"
   dgquery: |-
     query {
-      queryUserSecret(func: uid(UserSecretRoot), orderasc: UserSecret.aSecret, first: 1) {
+      queryUserSecret(func: uid(UserSecretRoot), orderasc: UserSecret.aSecret) {
         id : uid
         ownedBy : UserSecret.ownedBy
       }
-      UserSecretRoot as var(func: uid(UserSecret1)) @filter(uid(UserSecretAuth2))
+      UserSecretRoot as var(func: uid(UserSecret1), first: 1) @filter(uid(UserSecretAuth2))
       UserSecret1 as var(func: type(UserSecret)) @filter(eq(UserSecret.ownedBy, "user2"))
       UserSecretAuth2 as var(func: uid(UserSecret1)) @filter(eq(UserSecret.ownedBy, "user1")) @cascade
     }
@@ -843,11 +843,11 @@
     USER: "user1"
   dgquery: |-
     query {
-      queryMovie(func: uid(MovieRoot), orderasc: Movie.content, first: 10, offset: 10) {
+      queryMovie(func: uid(MovieRoot), orderasc: Movie.content) {
         content : Movie.content
         dgraph.uid : uid
       }
-      MovieRoot as var(func: uid(Movie1)) @filter((NOT (uid(MovieAuth2)) AND (uid(MovieAuth3) OR uid(MovieAuth4))))
+      MovieRoot as var(func: uid(Movie1), first: 10, offset: 10) @filter((NOT (uid(MovieAuth2)) AND (uid(MovieAuth3) OR uid(MovieAuth4))))
       Movie1 as var(func: type(Movie)) @filter(eq(Movie.content, "A. N. Author"))
       MovieAuth2 as var(func: uid(Movie1)) @filter(eq(Movie.hidden, true)) @cascade
       MovieAuth3 as var(func: uid(Movie1)) @cascade {
@@ -878,7 +878,7 @@
     USER: "user1"
   dgquery: |-
     query {
-      queryMovie(func: uid(MovieRoot), orderasc: Movie.content, first: 10, offset: 10) @cascade {
+      queryMovie(func: uid(MovieRoot), orderasc: Movie.content) @cascade {
         content : Movie.content
         regionsAvailable : Movie.regionsAvailable @filter(uid(Region2)) (orderasc: Region.name, first: 10, offset: 10) {
           name : Region.name
@@ -887,7 +887,7 @@
         }
         dgraph.uid : uid
       }
-      MovieRoot as var(func: uid(Movie3)) @filter((NOT (uid(MovieAuth4)) AND (uid(MovieAuth5) OR uid(MovieAuth6))))
+      MovieRoot as var(func: uid(Movie3), first: 10, offset: 10) @filter((NOT (uid(MovieAuth4)) AND (uid(MovieAuth5) OR uid(MovieAuth6))))
       Movie3 as var(func: type(Movie)) @filter(eq(Movie.content, "MovieXYZ"))
       MovieAuth4 as var(func: uid(Movie3)) @filter(eq(Movie.hidden, true)) @cascade
       MovieAuth5 as var(func: uid(Movie3)) @cascade {
@@ -931,7 +931,7 @@
     USER: "user1"
   dgquery: |-
     query {
-      queryMovie(func: uid(MovieRoot), orderasc: Movie.content, first: 10, offset: 10) {
+      queryMovie(func: uid(MovieRoot), orderasc: Movie.content) {
         content : Movie.content
         regionsAvailable : Movie.regionsAvailable @filter(uid(Region7)) (orderasc: Region.name, first: 10, offset: 10) @cascade {
           name : Region.name
@@ -951,7 +951,7 @@
         }
         dgraph.uid : uid
       }
-      MovieRoot as var(func: uid(Movie8)) @filter((NOT (uid(MovieAuth9)) AND (uid(MovieAuth10) OR uid(MovieAuth11))))
+      MovieRoot as var(func: uid(Movie8), first: 10, offset: 10) @filter((NOT (uid(MovieAuth9)) AND (uid(MovieAuth10) OR uid(MovieAuth11))))
       Movie8 as var(func: type(Movie)) @filter(eq(Movie.content, "MovieXYZ"))
       MovieAuth9 as var(func: uid(Movie8)) @filter(eq(Movie.hidden, true)) @cascade
       MovieAuth10 as var(func: uid(Movie8)) @cascade {
@@ -1526,12 +1526,12 @@
     USER: "Random"
   dgquery: |-
     query {
-      queryPost(func: uid(PostRoot), orderdesc: Post.text, first: 10, offset: 5) {
+      queryPost(func: uid(PostRoot), orderdesc: Post.text) {
         dgraph.type
         text : Post.text
         dgraph.uid : uid
       }
-      PostRoot as var(func: uid(Post1)) @filter(((uid(QuestionAuth2) AND uid(QuestionAuth3)) OR uid(FbPostAuth4) OR uid(AnswerAuth5)))
+      PostRoot as var(func: uid(Post1), first: 10, offset: 5) @filter(((uid(QuestionAuth2) AND uid(QuestionAuth3)) OR uid(FbPostAuth4) OR uid(AnswerAuth5)))
       Post1 as var(func: type(Post)) @filter(eq(Post.text, "A Post"))
       Question1 as var(func: type(Question))
       QuestionAuth2 as var(func: uid(Question1)) @filter(eq(Question.answered, true)) @cascade {

graphql/resolve/query_rewriter.go

@@ -730,9 +730,11 @@ func (authRw *authRewriter) addAuthQueries(
 			Args: []gql.Arg{{Value: authRw.varName}},
 		},
 		Filter: filter,
+		Args:   dgQuery[0].Args,
 	}
 
 	dgQuery[0].Filter = nil
+	dgQuery[0].Args = nil
 
 	// The user query starts from the var query generated above and is filtered
 	// by the the filter generated from auth processing, so now we build

query/query.go

@@ -1992,7 +1992,18 @@ func ProcessGraph(ctx context.Context, sg, parent *SubGraph, rch chan error) {
 	if len(sg.Attr) > 0 {
 		suffix += "." + sg.Attr
 	}
-	span := otrace.FromContext(ctx)
+	// queries like `Users as var(func: ...)` have Alias = var and don't have an attr. Instead, they
+	// would have Var = Users. So, if there are a lot of such queries in a single request,
+	// then it is easier to identify them in traces if we also use Var to construct the span name.
+	if len(sg.Params.Var) > 0 {
+		suffix += "." + sg.Params.Var
+	}
+	// starting a span for every sub-graph that is processed creates an execution tree in jaeger UI,
+	// which makes it very easier to understand the flow of request execution.
+	ctx, span := otrace.StartSpan(ctx, "query.ProcessGraph."+suffix)
+	defer span.End()
+
+	// span timer doesn't show up in jaeger UI directly. Instead, it is part of logs for each span.
 	stop := x.SpanTimer(span, "query.ProcessGraph"+suffix)
 	defer stop()