feat(alpha): support RDF response via http query request (#8004) (#8639)

Fixes #8529
Closes: DGRAPHCORE-223

inspired from #8004

Co-authored-by: Aman Mangal <aman@dgraph.io>

Makefile

@@ -30,7 +30,7 @@ GOPATH         ?= $(shell go env GOPATH)
 ######################
 DGRAPH_VERSION ?= local
 
-.PHONY: all 
+.PHONY: all
 all: dgraph
 
 .PHONY: dgraph

dgraph/cmd/alpha/http.go

@@ -244,6 +244,18 @@ func queryHandler(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
+	// If rdf is set true, then response will be in rdf format.
+	respFormat := r.URL.Query().Get("respFormat")
+	switch respFormat {
+	case "", "json":
+		req.RespFormat = api.Request_JSON
+	case "rdf":
+		req.RespFormat = api.Request_RDF
+	default:
+		x.SetStatus(w, x.ErrorInvalidRequest, fmt.Sprintf("invalid value [%v] for parameter respFormat", respFormat))
+		return
+	}
+
 	// Core processing happens here.
 	resp, err := (&edgraph.Server{}).QueryNoGrpc(ctx, &req)
 	if err != nil {
@@ -273,7 +285,17 @@ func queryHandler(w http.ResponseWriter, r *http.Request) {
 		x.Check2(out.Write(js))
 	}
 	x.Check2(out.WriteRune('{'))
-	writeEntry("data", resp.Json)
+	if respFormat == "rdf" {
+		// In Json, []byte marshals into a base64 data. We instead Marshal it as a string.
+		// json.Marshal is therefore necessary here. We also do not want to escape <,>.
+		var buf bytes.Buffer
+		encoder := json.NewEncoder(&buf)
+		encoder.SetEscapeHTML(false)
+		x.Check(encoder.Encode(string(resp.Rdf)))
+		writeEntry("data", buf.Bytes())
+	} else {
+		writeEntry("data", resp.Json)
+	}
 	x.Check2(out.WriteRune(','))
 	writeEntry("extensions", js)
 	x.Check2(out.WriteRune('}'))

dgraph/cmd/alpha/http_test.go

@@ -164,11 +164,12 @@ func queryWithGz(queryText, contentType, debug, timeout string, gzReq, gzResp bo
 }
 
 type queryInp struct {
-	body  string
-	typ   string
-	debug string
-	ts    uint64
-	hash  string
+	body    string
+	typ     string
+	debug   string
+	ts      uint64
+	hash    string
+	respFmt string
 }
 
 type tsInfo struct {
@@ -191,6 +192,9 @@ func queryWithTsForResp(inp queryInp) (string, *tsInfo, *http.Response, error) {
 		params = append(params, fmt.Sprintf("startTs=%v", strconv.FormatUint(inp.ts, 10)))
 		params = append(params, fmt.Sprintf("hash=%s", inp.hash))
 	}
+	if inp.respFmt != "" {
+		params = append(params, fmt.Sprintf("respFormat=%s", inp.respFmt))
+	}
 	url := addr + "/query?" + strings.Join(params, "&")
 
 	_, body, resp, err := runWithRetriesForResp("POST", inp.typ, url, inp.body)
@@ -205,12 +209,9 @@ func queryWithTsForResp(inp queryInp) (string, *tsInfo, *http.Response, error) {
 	startTs := r.Extensions.Txn.StartTs
 	hash := r.Extensions.Txn.Hash
 
-	// Remove the extensions.
-	r2 := res{
-		Data: r.Data,
-	}
+	// Remove the extensions
+	r2 := res{Data: r.Data}
 	output, err := json.Marshal(r2)
-
 	return string(output), &tsInfo{ts: startTs, hash: hash}, resp, err
 }
 
@@ -985,3 +986,54 @@ func TestQueryBackwardCompatibleWithGraphqlPlusMinusHeader(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, "2", resp.Header.Get(x.DgraphCostHeader))
 }
+
+func TestQueryRdfData(t *testing.T) {
+	require.NoError(t, dropAll())
+	require.NoError(t, alterSchema(`name: string @index(term) .`))
+
+	// empty RDF response
+	q1 := `
+	{
+	  balances(func: anyofterms(name, "Alice Bob")) {
+	    name
+	    balance
+	  }
+	}`
+	resp, _, err := queryWithTs(queryInp{body: q1, typ: "application/dql", respFmt: "rdf"})
+	require.NoError(t, err)
+	require.Equal(t, `{"data":""}`, resp)
+
+	m1 := `
+    {
+	  set {
+		_:bob <name> "Bob \"<the builder>\"" .
+		_:bob <balance> "110" .
+		_:alice <balance> "60" .
+	  }
+	}`
+	_, err = mutationWithTs(mutationInp{body: m1, typ: "application/rdf", commitNow: true})
+	require.NoError(t, err)
+
+	// json query
+	resp, _, err = queryWithTs(queryInp{body: q1, typ: "application/dql"})
+	require.NoError(t, err)
+	require.Equal(t, `{"data":{"balances":[{"name":"Bob \"\u003cthe builder\u003e\"","balance":"110"}]}}`, resp)
+
+	// rdf query
+	resp, _, err = queryWithTs(queryInp{body: q1, typ: "application/dql", respFmt: "rdf"})
+	require.NoError(t, err)
+	var r2 struct {
+		Data string `json:"data"`
+	}
+	require.NoError(t, json.Unmarshal([]byte(resp), &r2))
+
+	// we apply the same RDF mutation and it should work
+	require.NoError(t, dropAll())
+	require.NoError(t, alterSchema(`name: string @index(term) .`))
+	_, err = mutationWithTs(mutationInp{body: `{set {` + r2.Data + `}}`, typ: "application/rdf", commitNow: true})
+	require.NoError(t, err)
+
+	resp, _, err = queryWithTs(queryInp{body: q1, typ: "application/dql"})
+	require.NoError(t, err)
+	require.Equal(t, `{"data":{"balances":[{"name":"Bob \"\u003cthe builder\u003e\"","balance":"110"}]}}`, resp)
+}