feat(dgraph): Add suport for RDF query.

edgraph/server.go

@@ -1074,6 +1074,8 @@ func processQuery(ctx context.Context, qc *queryContext) (*api.Response, error)
 			respMap["types"] = formatTypes(er.Types)
 		}
 		resp.Json, err = json.Marshal(respMap)
+	} else if qc.req.RdfFormat {
+		resp.Rdf, err = query.ToRDF(qc.latency, er.Subgraphs)
 	} else {
 		resp.Json, err = query.ToJson(qc.latency, er.Subgraphs)
 	}

go.mod

@@ -17,7 +17,7 @@ require (
 	github.com/blevesearch/snowballstem v0.0.0-20180110192139-26b06a2c243d // indirect
 	github.com/codahale/hdrhistogram v0.0.0-20161010025455-3a0bb77429bd
 	github.com/dgraph-io/badger/v2 v2.0.1-rc1.0.20200715005050-3ffaf3cd1d4a
-	github.com/dgraph-io/dgo/v200 v200.0.0-20200401175452-e463f9234453
+	github.com/dgraph-io/dgo/v200 v200.0.0-20200720091212-f41d047addd1
 	github.com/dgraph-io/ristretto v0.0.3-0.20200630154024-f66de99634de
 	github.com/dgrijalva/jwt-go v3.2.0+incompatible
 	github.com/dgrijalva/jwt-go/v4 v4.0.0-preview1

go.sum

@@ -78,12 +78,10 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dgraph-io/badger v1.6.0 h1:DshxFxZWXUcO0xX476VJC07Xsr6ZCBVRHKZ93Oh7Evo=
 github.com/dgraph-io/badger v1.6.0/go.mod h1:zwt7syl517jmP8s94KqSxTlM6IMsdhYy6psNgSztDR4=
-github.com/dgraph-io/badger/v2 v2.0.1-rc1.0.20200711090415-0dfb8b45d4a4 h1:M85aROJxDOXmp8mZQN6x04EraKDGOF2RL3ox/6LZdjo=
-github.com/dgraph-io/badger/v2 v2.0.1-rc1.0.20200711090415-0dfb8b45d4a4/go.mod h1:26P/7fbL4kUZVEVKLAKXkBXKOydDmM2p1e+NhhnBCAE=
 github.com/dgraph-io/badger/v2 v2.0.1-rc1.0.20200715005050-3ffaf3cd1d4a h1:k8A4B5IEFzH33Px1N7K0FpMszEFTZGQb7HCRBslMB+s=
 github.com/dgraph-io/badger/v2 v2.0.1-rc1.0.20200715005050-3ffaf3cd1d4a/go.mod h1:26P/7fbL4kUZVEVKLAKXkBXKOydDmM2p1e+NhhnBCAE=
-github.com/dgraph-io/dgo/v200 v200.0.0-20200401175452-e463f9234453 h1:DTgOrw91nMIukDm/WEvdobPLl0LgeDd/JE66+24jBks=
-github.com/dgraph-io/dgo/v200 v200.0.0-20200401175452-e463f9234453/go.mod h1:Co+FwJrnndSrPORO8Gdn20dR7FPTfmXr0W/su0Ve/Ig=
+github.com/dgraph-io/dgo/v200 v200.0.0-20200720091212-f41d047addd1 h1:bB3SjXpTJ7YcYheynrAlc5K0nlmNgygsj8WHlhRncig=
+github.com/dgraph-io/dgo/v200 v200.0.0-20200720091212-f41d047addd1/go.mod h1:Co+FwJrnndSrPORO8Gdn20dR7FPTfmXr0W/su0Ve/Ig=
 github.com/dgraph-io/ristretto v0.0.3-0.20200630154024-f66de99634de h1:t0UHb5vdojIDUqktM6+xJAfScFBsVpXZmqC9dsgJmeA=
 github.com/dgraph-io/ristretto v0.0.3-0.20200630154024-f66de99634de/go.mod h1:KPxhHT9ZxKefz+PCeOGsrHpl1qZ7i70dGTu2u+Ahh6E=
 github.com/dgrijalva/jwt-go v3.2.0+incompatible h1:7qlOGliEKZXTDg6OTjfoBKDXWrumCAMpl/TFQ4/5kLM=

query/common_test.go

@@ -63,6 +63,17 @@ func processQuery(ctx context.Context, t *testing.T, query string) (string, erro
 	return string(jsonResponse), err
 }
 
+func processQueryRDF(ctx context.Context, t *testing.T, query string) (string, error) {
+	txn := client.NewTxn()
+	defer txn.Discard(ctx)
+
+	res, err := txn.Do(ctx, &api.Request{
+		Query:     query,
+		RdfFormat: true,
+	})
+	return string(res.Rdf), err
+}
+
 func processQueryNoErr(t *testing.T, query string) string {
 	res, err := processQuery(context.Background(), t, query)
 	require.NoError(t, err)

query/outputrdf.go

@@ -0,0 +1,166 @@
+/*
+ * Copyright 2017-2020 Dgraph Labs, Inc. and Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package query
+
+import (
+	"fmt"
+
+	"github.com/dgraph-io/dgraph/algo"
+	"github.com/dgraph-io/dgraph/protos/pb"
+	"github.com/dgraph-io/dgraph/types"
+	"github.com/pkg/errors"
+)
+
+// ToRDF converts the given subgraph list into rdf format.
+func ToRDF(l *Latency, sgl []*SubGraph) ([]byte, error) {
+	output := ""
+	for _, sg := range sgl {
+		// Skip parent graph. we don't want parent values.
+		for _, child := range sg.Children {
+			if err := castToRDF(&output, child); err != nil {
+				return nil, err
+			}
+		}
+
+	}
+	return []byte(output), nil
+}
+
+// castToRDF converts the given subgraph to RDF and appends to the
+// output string.
+func castToRDF(output *string, sg *SubGraph) error {
+
+	uidCount := sg.Attr == "uid" && sg.Params.DoCount && sg.IsInternal()
+	if uidCount {
+		return errors.New("uid count is not supported in the rdf output format")
+	}
+
+	if sg.Params.Normalize {
+		return errors.New("normalize directive is not supported in the rdf output format")
+	}
+
+	if sg.Params.IgnoreReflex {
+		return errors.New("ignorereflex directive is not supported in the rdf output format")
+	}
+
+	if sg.SrcFunc != nil && sg.SrcFunc.Name == "checkpwd" {
+		return errors.New("chkpwd function is not supported in the rdf output format")
+	}
+
+	if sg.SrcUIDs != nil {
+		// Get RDF for the given subgraph.
+		if err := rdfForSubgraph(output, sg); err != nil {
+			return err
+		}
+	}
+
+	// Recursively cnvert RDF for the children graph.
+	for _, child := range sg.Children {
+		err := castToRDF(output, child)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// rdfForSubgraph generates RDF and appends to the output parameter.
+func rdfForSubgraph(output *string, sg *SubGraph) error {
+	for i, uid := range sg.SrcUIDs.Uids {
+		if sg.Params.IgnoreResult {
+			// Skip ignored values.
+			continue
+		}
+
+		if sg.IsInternal() {
+			if sg.Params.Expand != "" {
+				continue
+			}
+			// Check if we have val for the given uid. If you got uid then populate
+			// the rdf.
+			val, ok := sg.Params.UidToVal[uid]
+			if !ok && val.Value == nil {
+				continue
+			}
+			outputval, err := valToBytes(val)
+			if err != nil {
+				return err
+			}
+			*output += fmt.Sprintf("<%#x> <%s> %s .\n", uid, sg.aggWithVarFieldName(),
+				string(outputval))
+			continue
+		}
+
+		switch {
+		case len(sg.counts) > 0:
+			// Add count rdf.
+			rdfForCount(output, uid, sg.counts[i], sg)
+		case i < len(sg.uidMatrix) && len(sg.uidMatrix[i].Uids) != 0:
+			// Add posting list relation.
+			rdfForUIDList(output, uid, sg.uidMatrix[i], sg)
+		case i < len(sg.valueMatrix):
+			// TODO: add facet.
+			rdfForValueList(output, uid, sg.valueMatrix[i], sg.fieldName())
+		}
+	}
+	return nil
+}
+
+// rdfForCount returns rdf for count fucntion.
+func rdfForCount(output *string, subject uint64, count uint32, sg *SubGraph) {
+	fieldName := sg.Params.Alias
+	if fieldName == "" {
+		fieldName = fmt.Sprintf("count(%s)", sg.Attr)
+	}
+	*output += fmt.Sprintf("<%#x> <%s> %d .\n", subject, fieldName, count)
+}
+
+// rdfForUIDList returns rdf for uid list.
+func rdfForUIDList(output *string, subject uint64, list *pb.List, sg *SubGraph) {
+	for _, destUID := range list.Uids {
+		if algo.IndexOf(sg.DestUIDs, destUID) < 0 {
+			// This uid is filtered.
+			continue
+		}
+		// TODO: do the right RDF format.
+		*output += fmt.Sprintf("<%#x> <%s> <%#x> .\n", subject, sg.fieldName(), destUID)
+	}
+}
+
+// rdfForValueList returns rdf for the value list.
+func rdfForValueList(output *string, subject uint64, valueList *pb.ValueList, attr string) error {
+	if attr == "uid" {
+		*output += fmt.Sprintf("<%#x> <%s> <%#x> .\n", subject, attr, subject)
+		return nil
+	}
+	for _, destValue := range valueList.Values {
+		val, err := convertWithBestEffort(destValue, attr)
+		if err != nil {
+			return err
+		}
+		outputval, err := valToBytes(val)
+		if err != nil {
+			return err
+		}
+		switch val.Tid {
+		case types.UidID:
+			*output += fmt.Sprintf("<%#x> <%s> <%s> .\n", subject, attr, string(outputval))
+		default:
+			*output += fmt.Sprintf("<%#x> <%s> %s .\n", subject, attr, string(outputval))
+		}
+	}
+	return nil
+}

query/rdf_result_test.go

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2020 Dgraph Labs, Inc. and Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package query
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestRDFResult(t *testing.T) {
+	query := `{
+		friends_15_and_19(func: uid(1)) {
+		  name
+		  friend @filter(ge(age, 15) AND lt(age, 19)) {
+			  name
+			  age
+		  }
+		}
+	  }`
+
+	rdf, err := processQueryRDF(context.Background(), t, query)
+	require.NoError(t, err)
+	require.Equal(t, string(rdf), `<0x1> <name> "Michonne" .
+<0x1> <friend> <0x17> .
+<0x1> <friend> <0x18> .
+<0x1> <friend> <0x19> .
+<0x17> <name> "Rick Grimes" .
+<0x18> <name> "Glenn Rhee" .
+<0x19> <name> "Daryl Dixon" .
+<0x17> <age> 15 .
+<0x18> <age> 15 .
+<0x19> <age> 17 .
+`)
+}