Add support for Conditional Upsert

dgraph/cmd/alpha/http.go

@@ -326,6 +326,13 @@ func mutationHandler(w http.ResponseWriter, r *http.Request) {
 				return
 			}
 		}
+		if condText, ok := ms["cond"]; ok && condText != nil {
+			mu.Query, err = strconv.Unquote(string(condText.bs))
+			if err != nil {
+				x.SetStatus(w, x.ErrorInvalidRequest, err.Error())
+				return
+			}
+		}
 
 	case "application/rdf":
 		// Parse N-Quads.

dgraph/cmd/alpha/upsert_test.go

@@ -21,9 +21,8 @@ import (
 	"sync"
 	"testing"
 
-	"github.com/dgraph-io/dgraph/testutil"
-
 	"github.com/dgraph-io/dgo/y"
+	"github.com/dgraph-io/dgraph/testutil"
 	"github.com/stretchr/testify/require"
 )
 
@@ -794,3 +793,68 @@ upsert {
 	_, _, _, err := mutationWithTs(m, "application/rdf", false, true, true, 0)
 	require.NoError(t, err)
 }
+
+func TestConditionalUpsertExample0(t *testing.T) {
+	require.NoError(t, dropAll())
+	require.NoError(t, alterSchema(`email: string @index(exact) .`))
+
+	// Mutation with wrong name
+	m1 := `
+upsert {
+  mutation {
+    set {
+      uid(v) <name> "Wrong" .
+      uid(v) <email> "ashish@dgraph.io" .
+    }
+  }
+
+  query {
+    me(func: eq(email, "ashish@dgraph.io")) {
+      v as uid
+    }
+  }
+}`
+	keys, preds, _, err := mutationWithTs(m1, "application/rdf", false, true, true, 0)
+	require.NoError(t, err)
+	require.True(t, len(keys) == 0)
+	require.True(t, contains(preds, "email"))
+	require.True(t, contains(preds, "name"))
+
+	// query should return the wrong name
+	q1 := `
+{
+  q(func: has(email)) {
+    uid
+    name
+    email
+  }
+}`
+	res, _, err := queryWithTs(q1, "application/graphql+-", "", 0)
+	require.NoError(t, err)
+	require.Contains(t, res, "Wrong")
+
+	// mutation with correct name
+	m2 := `
+upsert {
+  mutation @if(eq(len(v), 1)) {
+    set {
+      uid(v) <name> "Ashish" .
+    }
+  }
+
+  query {
+    me(func: eq(email, "ashish@dgraph.io")) {
+      v as uid
+    }
+  }
+}`
+	keys, preds, _, err = mutationWithTs(m2, "application/rdf", false, true, true, 0)
+	require.NoError(t, err)
+	require.True(t, len(keys) == 0)
+	require.True(t, contains(preds, "name"))
+
+	// query should return correct name
+	res, _, err = queryWithTs(q1, "application/graphql+-", "", 0)
+	require.NoError(t, err)
+	require.Contains(t, res, "Ashish")
+}

edgraph/server.go

@@ -571,45 +571,74 @@ func (s *Server) doMutate(ctx context.Context, mu *api.Mutation, authorize bool)
 func doQueryInUpsert(ctx context.Context, mu *api.Mutation, gmu *gql.Mutation) (
 	*query.Latency, error) {
 
+	isThisUpsert := mu.Query != ""
+	isThisCondUpsert := strings.TrimSpace(mu.Cond) != ""
+
 	l := &query.Latency{}
-	if mu.Query == "" {
+	if !isThisUpsert {
 		return l, nil
 	}
 
+	queryWithIf := mu.Query
 	needVars := findVars(gmu)
+	if isThisCondUpsert {
+		// currently we do not have support for @if directly.
+		cond := strings.Replace(mu.Cond, "@if", "@filter", 1)
+
+		// remove the trailing closing brace and add the query to
+		// find out whether the if condition is true or false.
+		queryWithIf = strings.TrimSuffix(strings.TrimSpace(mu.Query), "}") +
+			` var(func: uid(0x01)) ` + cond + ` { __uid__ as uid }` + `}`
+		needVars = append(needVars, "__uid__")
+	}
+
 	startParsingTime := time.Now()
 	parsedReq, err := gql.ParseWithNeedVars(gql.Request{
-		Str:       mu.Query,
+		Str:       queryWithIf,
 		Variables: make(map[string]string),
 	}, needVars)
 	l.Parsing += time.Since(startParsingTime)
 	if err != nil {
-		return nil, errors.Wrapf(err, "while parsing query: %q", mu.Query)
+		return nil, errors.Wrapf(err, "while parsing query: %q", queryWithIf)
 	}
 	if err := validateQuery(parsedReq.Query); err != nil {
-		return nil, errors.Wrapf(err, "while validating query: %q", mu.Query)
+		return nil, errors.Wrapf(err, "while validating query: %q", queryWithIf)
 	}
 
 	qr := query.Request{Latency: l, GqlQuery: &parsedReq, ReadTs: mu.StartTs}
 	if err := qr.ProcessQuery(ctx); err != nil {
-		return nil, errors.Wrapf(err, "while processing query: %q", mu.Query)
+		return nil, errors.Wrapf(err, "while processing query: %q", queryWithIf)
 	}
 
 	if len(qr.Vars) <= 0 {
 		return nil, errors.Errorf("upsert query block has no variables")
 	}
 
-	// TODO(Aman): allow multiple values for each variable.
 	// If a variable doesn't have any UID, we generate one ourselves later.
-	varToUID := make(map[string]string)
+	varToUID := make(map[string][]string)
 	for name, v := range qr.Vars {
 		if v.Uids == nil {
 			continue
 		}
-		if len(v.Uids.Uids) > 1 {
-			return nil, errors.Errorf("more than one values found for var (%s)", name)
-		} else if len(v.Uids.Uids) == 1 {
-			varToUID[name] = fmt.Sprintf("%d", v.Uids.Uids[0])
+
+		if len(v.Uids.Uids) > 0 {
+			uids := make([]string, len(v.Uids.Uids))
+			for i, u := range v.Uids.Uids {
+				uids[i] = fmt.Sprintf("%d", u)
+			}
+
+			varToUID[name] = uids
+		}
+	}
+
+	// Conditional mutation, we simply return in case condition is false
+	if isThisCondUpsert {
+		v, ok := qr.Vars["__uid__"]
+		isMut := ok && (len(v.Uids.Uids) == 1)
+		if !isMut {
+			gmu.Set = nil
+			gmu.Del = nil
+			return l, nil
 		}
 	}
 
@@ -649,39 +678,63 @@ func findVars(gmu *gql.Mutation) []string {
 // updateMutations does following transformations:
 //   * uid(v) -> 0x123     -- If v is defined in query block
 //   * uid(v) -> _:uid(v)  -- Otherwise
-func updateMutations(gmu *gql.Mutation, varToUID map[string]string) {
-	getNewVal := func(s string) string {
+func updateMutations(gmu *gql.Mutation, varToUID map[string][]string) {
+	getNewVal := func(s string) []string {
 		if strings.HasPrefix(s, "uid(") {
 			varName := s[4 : len(s)-1]
-			if uid, ok := varToUID[varName]; ok {
-				return uid
+			if uids, ok := varToUID[varName]; ok {
+				return uids
 			}
 
-			return "_:" + s
+			return []string{"_:" + s}
 		}
 
-		return s
+		return []string{s}
+	}
+
+	getNewNQuad := func(nq *api.NQuad, s, o string) *api.NQuad {
+		// The following copy is fine because we only modify Subject and ObjectId.
+		// The pointer values are not modified across different copies of NQuad.
+		n := *nq
+
+		n.Subject = s
+		n.ObjectId = o
+		return &n
 	}
 
 	// Remove the mutations from gmu.Del when no UID was found.
-	gmuDel := gmu.Del[:0]
+	gmuDel := make([]*api.NQuad, 0, len(gmu.Del))
 	for _, nq := range gmu.Del {
-		nq.Subject = getNewVal(nq.Subject)
-		nq.ObjectId = getNewVal(nq.ObjectId)
-
-		if !strings.HasPrefix(nq.Subject, "_:uid(") &&
-			!strings.HasPrefix(nq.ObjectId, "_:uid(") {
+		newSubs := getNewVal(nq.Subject)
+		newObs := getNewVal(nq.ObjectId)
+
+		for _, s := range newSubs {
+			for _, o := range newObs {
+				// Blank node has no meaning in case of deletion.
+				if strings.HasPrefix(s, "_:uid(") ||
+					strings.HasPrefix(o, "_:uid(") {
+					continue
+				}
 
-			gmuDel = append(gmuDel, nq)
+				gmuDel = append(gmuDel, getNewNQuad(nq, s, o))
+			}
 		}
 	}
 	gmu.Del = gmuDel
 
 	// Update the values in mutation block from the query block.
+	gmuSet := make([]*api.NQuad, 0, len(gmu.Set))
 	for _, nq := range gmu.Set {
-		nq.Subject = getNewVal(nq.Subject)
-		nq.ObjectId = getNewVal(nq.ObjectId)
+		newSubs := getNewVal(nq.Subject)
+		newObs := getNewVal(nq.ObjectId)
+
+		for _, s := range newSubs {
+			for _, o := range newObs {
+				gmuSet = append(gmuSet, getNewNQuad(nq, s, o))
+			}
+		}
 	}
+	gmu.Set = gmuSet
 }
 
 // Query handles queries and returns the data.

gql/parser_mutation.go

@@ -39,11 +39,11 @@ func ParseMutation(mutation string) (mu *api.Mutation, err error) {
 	item := it.Item()
 	switch item.Typ {
 	case itemUpsertBlock:
-		if mu, err = ParseUpsertBlock(it); err != nil {
+		if mu, err = parseUpsertBlock(it); err != nil {
 			return nil, err
 		}
 	case itemLeftCurl:
-		if mu, err = ParseMutationBlock(it); err != nil {
+		if mu, err = parseMutationBlock(it); err != nil {
 			return nil, err
 		}
 	default:
@@ -58,11 +58,11 @@ func ParseMutation(mutation string) (mu *api.Mutation, err error) {
 	return mu, nil
 }
 
-// ParseUpsertBlock parses the upsert block
-func ParseUpsertBlock(it *lex.ItemIterator) (*api.Mutation, error) {
+// parseUpsertBlock parses the upsert block
+func parseUpsertBlock(it *lex.ItemIterator) (*api.Mutation, error) {
 	var mu *api.Mutation
-	var queryText string
-	var queryFound bool
+	var queryText, condText string
+	var queryFound, condFound bool
 
 	// ===>upsert<=== {...}
 	if !it.Next() {
@@ -86,6 +86,7 @@ func ParseUpsertBlock(it *lex.ItemIterator) (*api.Mutation, error) {
 				return nil, errors.Errorf("Query op not found in upsert block")
 			} else {
 				mu.Query = queryText
+				mu.Cond = condText
 				return mu, nil
 			}
 
@@ -109,8 +110,23 @@ func ParseUpsertBlock(it *lex.ItemIterator) (*api.Mutation, error) {
 			if !it.Next() {
 				return nil, errors.Errorf("Unexpected end of upsert block")
 			}
+
+			// upsert { mutation ===>@if(...)<=== {....} query{...}}
+			item = it.Item()
+			if item.Typ == itemUpsertBlockOpContent {
+				if condFound {
+					return nil, errors.Errorf("Multiple @if directive inside upsert block")
+				}
+				condFound = true
+				condText = item.Val
+				if !it.Next() {
+					return nil, errors.Errorf("Unexpected end of upsert block")
+				}
+			}
+
+			// upsert @if(...) ===>{<=== ....}
 			var err error
-			if mu, err = ParseMutationBlock(it); err != nil {
+			if mu, err = parseMutationBlock(it); err != nil {
 				return nil, err
 			}
 
@@ -133,8 +149,8 @@ func ParseUpsertBlock(it *lex.ItemIterator) (*api.Mutation, error) {
 	return nil, errors.Errorf("Invalid upsert block")
 }
 
-// ParseMutationBlock parses the mutation block
-func ParseMutationBlock(it *lex.ItemIterator) (*api.Mutation, error) {
+// parseMutationBlock parses the mutation block
+func parseMutationBlock(it *lex.ItemIterator) (*api.Mutation, error) {
 	var mu api.Mutation
 
 	item := it.Item()