feat(GraphQL): add support for between filter in GraphQL (#6651)

Fixes GRAPHQL-667.

This PR extend support for `between` filter in GraphQL. This filter can be used for all scalars when indexed in a type (`exact` index for `String`). For the given type
```
type Student{
   age: Int @search
   name: String @search(by: [exact])
}
```
`between filter` can be used both on the `age` and `name` field. for eg:
```
queryStudent(fitler: {age: between: {min: 10, max: 20}}){
    age
    name
}
```
and
```
queryStudent(fitler: {name: between: {min: "abc", max: "def"}}){
    age
    name
}
```

graphql/e2e/common/common.go

@@ -139,6 +139,7 @@ type post struct {
 	Title       string    `json:"title,omitempty"`
 	Text        string    `json:"text,omitempty"`
 	Tags        []string  `json:"tags,omitempty"`
+	Topic       string    `json:"topic,omitempty"`
 	NumLikes    int       `json:"numLikes,omitempty"`
 	NumViews    int64     `json:"numViews,omitempty"`
 	IsPublished bool      `json:"isPublished,omitempty"`
@@ -298,6 +299,8 @@ func RunAll(t *testing.T) {
 	t.Run("multiple search indexes wrong field", multipleSearchIndexesWrongField)
 	t.Run("hash search", hashSearch)
 	t.Run("in filter", inFilter)
+	t.Run("between filter", betweenFilter)
+	t.Run("deep between filter", deepBetweenFilter)
 	t.Run("deep filter", deepFilter)
 	t.Run("deep has filter", deepHasFilter)
 	t.Run("many queries", manyQueries)

graphql/e2e/common/query.go

@@ -432,6 +432,74 @@ func inFilter(t *testing.T) {
 	deleteGqlType(t, "State", deleteFilter, 2, nil)
 }
 
+func betweenFilter(t *testing.T) {
+	queryPostParams := &GraphQLParams{
+		Query: `query {
+			queryPost(filter: {numLikes: {between: {min:90, max:100}}}) {
+				title
+				numLikes
+			}
+		}`,
+	}
+
+	gqlResponse := queryPostParams.ExecuteAsPost(t, GraphqlURL)
+	RequireNoGQLErrors(t, gqlResponse)
+
+	var result struct {
+		QueryPost []*post
+	}
+
+	err := json.Unmarshal([]byte(gqlResponse.Data), &result)
+	require.NoError(t, err)
+	require.Equal(t, 1, len(result.QueryPost))
+
+	expected := &post{
+		Title:    "Introducing GraphQL in Dgraph",
+		NumLikes: 100,
+	}
+
+	if diff := cmp.Diff(expected, result.QueryPost[0]); diff != "" {
+		t.Errorf("result mismatch (-want +got):\n%s", diff)
+	}
+}
+
+func deepBetweenFilter(t *testing.T) {
+	queryPostParams := &GraphQLParams{
+		Query: `query{
+			queryAuthor(filter: {reputation: {between: {min:6.0, max: 7.2}}}){
+			  name
+			  reputation
+			  posts(filter: {topic: {between: {min: "GraphQL", max: "GraphQL+-"}}}){
+				title
+				topic
+			  }
+			}
+		  }`,
+	}
+
+	gqlResponse := queryPostParams.ExecuteAsPost(t, GraphqlURL)
+	RequireNoGQLErrors(t, gqlResponse)
+
+	var result struct {
+		QueryAuthor []*author
+	}
+
+	err := json.Unmarshal([]byte(gqlResponse.Data), &result)
+	require.NoError(t, err)
+	require.Equal(t, 1, len(result.QueryAuthor))
+
+	expected := &author{
+		Name:       "Ann Author",
+		Reputation: 6.6,
+		Posts:      []*post{{Title: "Introducing GraphQL in Dgraph", Topic: "GraphQL"}},
+	}
+
+	if diff := cmp.Diff(expected, result.QueryAuthor[0]); diff != "" {
+		t.Errorf("result mismatch (-want +got):\n%s", diff)
+	}
+
+}
+
 func deepFilter(t *testing.T) {
 	getAuthorParams := &GraphQLParams{
 		Query: `query {

graphql/e2e/schema/generatedSchema.graphql

@@ -23,6 +23,31 @@ For example: "1985-04-12T23:20:50.52Z" represents 20 minutes and 50.52 seconds a
 """
 scalar DateTime
 
+input IntRange{
+	min: Int
+	max: Int
+}
+
+input FloatRange{
+	min: Float
+	max: Float
+}
+
+input Int64Range{
+	min: Int64
+	max: Int64
+}
+
+input DateTimeRange{
+	min: DateTime
+	max: DateTime
+}
+
+input StringRange{
+	min: String
+	max: String
+}
+
 enum DgraphIndex {
 	int
 	int64
@@ -114,6 +139,7 @@ input IntFilter {
 	lt: Int
 	ge: Int
 	gt: Int
+	between: IntRange
 }
 
 input Int64Filter {
@@ -122,6 +148,7 @@ input Int64Filter {
 	lt: Int64
 	ge: Int64
 	gt: Int64
+	between: Int64Range
 }
 
 input FloatFilter {
@@ -130,6 +157,7 @@ input FloatFilter {
 	lt: Float
 	ge: Float
 	gt: Float
+	between: FloatRange
 }
 
 input DateTimeFilter {
@@ -138,6 +166,7 @@ input DateTimeFilter {
 	lt: DateTime
 	ge: DateTime
 	gt: DateTime
+	between: DateTimeRange
 }
 
 input StringTermFilter {
@@ -161,6 +190,7 @@ input StringExactFilter {
 	lt: String
 	ge: String
 	gt: String
+	between: StringRange
 }
 
 input StringHashFilter {

graphql/resolve/query_rewriter.go

@@ -1071,9 +1071,9 @@ func buildFilter(typ schema.Type, filter map[string]interface{}) *gql.FilterTree
 					Child: []*gql.FilterTree{not},
 				})
 		default:
-			// It's a base case like:
-			// title: { anyofterms: "GraphQL" } ->  anyofterms(Post.title: "GraphQL")
-
+			//// It's a base case like:
+			//// title: { anyofterms: "GraphQL" } ->  anyofterms(Post.title: "GraphQL")
+			//// numLikes: { between : { min : 10,  max:100 }}
 			switch dgFunc := filter[field].(type) {
 			case map[string]interface{}:
 				// title: { anyofterms: "GraphQL" } ->  anyofterms(Post.title, "GraphQL")
@@ -1096,6 +1096,7 @@ func buildFilter(typ schema.Type, filter map[string]interface{}) *gql.FilterTree
 					for _, v := range vals {
 						args = append(args, gql.Arg{Value: maybeQuoteArg(fn, v)})
 					}
+
 				case "near":
 					//  For Geo type we have `near` filter which is written as follows:
 					// { near: { distance: 33.33, coordinate: { latitude: 11.11, longitude: 22.22 } } }
@@ -1108,6 +1109,14 @@ func buildFilter(typ schema.Type, filter map[string]interface{}) *gql.FilterTree
 					args = append(args, gql.Arg{Value: fmt.Sprintf("[%v,%v]", long, lat)},
 						gql.Arg{Value: fmt.Sprintf("%v", distance)})
 
+				case "between":
+					// numLikes: { between : { min : 10,  max:100 }} should be rewritten into
+					// 	between(numLikes,10,20). Order of arguments (min,max) is neccessary or
+					// it will return empty
+					vals := val.(map[string]interface{})
+					args = append(args, gql.Arg{Value: maybeQuoteArg(fn, vals["min"])},
+						gql.Arg{Value: maybeQuoteArg(fn, vals["max"])})
+
 				default:
 					args = append(args, gql.Arg{Value: maybeQuoteArg(fn, val)})
 				}

graphql/resolve/query_test.yaml

@@ -1267,6 +1267,51 @@
       }
     }
 
+-
+  name: "Between filter"
+  gqlquery: |
+    query {
+      queryPost(filter: { numLikes: { between : { min :10, max: 20 }}}) {
+        title
+        text
+      }
+    }
+  dgquery: |-
+    query {
+      queryPost(func: type(Post)) @filter(between(Post.numLikes, 10, 20)) {
+        title : Post.title
+        text : Post.text
+        dgraph.uid : uid
+      }
+    }
+
+-
+  name: "deep Between filter"
+  gqlquery: |
+    query{
+      queryAuthor(filter: {reputation: {between: {min:6.0, max: 7.2}}}){
+        name
+        reputation
+        posts(filter: {numLikes: {between: {min: 10, max: 100}}}){
+          title
+          numLikes
+        }
+      }
+    }
+  dgquery: |-
+    query {
+      queryAuthor(func: type(Author)) @filter(between(Author.reputation, 6, 7.2)) {
+        name : Author.name
+        reputation : Author.reputation
+        posts : Author.posts @filter(between(Post.numLikes, 10, 100)) {
+          title : Post.title
+          numLikes : Post.numLikes
+          dgraph.uid : uid
+        }
+        dgraph.uid : uid
+      }
+    }
+
 -
   name: "Filter with id inside and argument doesn't use uid func at root."
   gqlquery: |

graphql/schema/gqlschema.go

@@ -82,6 +82,31 @@ For example: "1985-04-12T23:20:50.52Z" represents 20 minutes and 50.52 seconds a
 """
 scalar DateTime
 
+input IntRange{
+	min: Int
+	max: Int
+}
+
+input FloatRange{
+	min: Float
+	max: Float
+}
+
+input Int64Range{
+	min: Int64
+	max: Int64
+}
+
+input DateTimeRange{
+	min: DateTime
+	max: DateTime
+}
+
+input StringRange{
+	min: String
+	max: String
+}
+
 enum DgraphIndex {
 	int
 	int64
@@ -173,6 +198,7 @@ input IntFilter {
 	lt: Int
 	ge: Int
 	gt: Int
+	between: IntRange
 }
 
 input Int64Filter {
@@ -181,6 +207,7 @@ input Int64Filter {
 	lt: Int64
 	ge: Int64
 	gt: Int64
+	between: Int64Range
 }
 
 input FloatFilter {
@@ -189,6 +216,7 @@ input FloatFilter {
 	lt: Float
 	ge: Float
 	gt: Float
+	between: FloatRange
 }
 
 input DateTimeFilter {
@@ -197,6 +225,7 @@ input DateTimeFilter {
 	lt: DateTime
 	ge: DateTime
 	gt: DateTime
+	between: DateTimeRange
 }
 
 input StringTermFilter {
@@ -220,6 +249,7 @@ input StringExactFilter {
 	lt: String
 	ge: String
 	gt: String
+	between: StringRange
 }
 
 input StringHashFilter {

graphql/schema/testdata/schemagen/output/authorization.graphql

@@ -34,6 +34,31 @@ For example: "1985-04-12T23:20:50.52Z" represents 20 minutes and 50.52 seconds a
 """
 scalar DateTime
 
+input IntRange{
+	min: Int
+	max: Int
+}
+
+input FloatRange{
+	min: Float
+	max: Float
+}
+
+input Int64Range{
+	min: Int64
+	max: Int64
+}
+
+input DateTimeRange{
+	min: DateTime
+	max: DateTime
+}
+
+input StringRange{
+	min: String
+	max: String
+}
+
 enum DgraphIndex {
 	int
 	int64
@@ -125,6 +150,7 @@ input IntFilter {
 	lt: Int
 	ge: Int
 	gt: Int
+	between: IntRange
 }
 
 input Int64Filter {
@@ -133,6 +159,7 @@ input Int64Filter {
 	lt: Int64
 	ge: Int64
 	gt: Int64
+	between: Int64Range
 }
 
 input FloatFilter {
@@ -141,6 +168,7 @@ input FloatFilter {
 	lt: Float
 	ge: Float
 	gt: Float
+	between: FloatRange
 }
 
 input DateTimeFilter {
@@ -149,6 +177,7 @@ input DateTimeFilter {
 	lt: DateTime
 	ge: DateTime
 	gt: DateTime
+	between: DateTimeRange
 }
 
 input StringTermFilter {
@@ -172,6 +201,7 @@ input StringExactFilter {
 	lt: String
 	ge: String
 	gt: String
+	between: StringRange
 }
 
 input StringHashFilter {