Enable Pagination(Support for offset and after)

gql/parser.go

@@ -32,6 +32,8 @@ type GraphQuery struct {
 	XID      string
 	Attr     string
 	First    int
+	Offset   int
+	After    uint64
 	Children []*GraphQuery
 }
 
@@ -240,7 +242,6 @@ func godeep(l *lex.Lexer, gq *GraphQuery) error {
 			if err != nil {
 				return err
 			}
-			// We only use argument 'first' for now.
 			for _, p := range args {
 				if p.Key == "first" {
 					count, err := strconv.ParseInt(p.Val, 0, 32)
@@ -249,6 +250,23 @@ func godeep(l *lex.Lexer, gq *GraphQuery) error {
 					}
 					curp.First = int(count)
 				}
+				if p.Key == "offset" {
+					count, err := strconv.ParseInt(p.Val, 0, 32)
+					if err != nil {
+						return err
+					}
+					if count < 0 {
+						return errors.New("offset cannot be less than 0")
+					}
+					curp.Offset = int(count)
+				}
+				if p.Key == "after" {
+					afterUid, err := strconv.ParseUint(p.Val, 0, 64)
+					if err != nil {
+						return err
+					}
+					curp.After = uint64(afterUid)
+				}
 			}
 		}
 	}

gql/parser_test.go

@@ -153,6 +153,98 @@ func TestParseFirst_error(t *testing.T) {
 	}
 }
 
+func TestParseAfter(t *testing.T) {
+	query := `
+	query {
+		user(_xid_: m.abcd) {
+			type.object.name
+			friends (first: 10, after: 3) {
+			}
+		}
+	}`
+	gq, _, err := Parse(query)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	if gq == nil {
+		t.Error("subgraph is nil")
+		return
+	}
+	if len(gq.Children) != 2 {
+		t.Errorf("Expected 2 children. Got: %v", len(gq.Children))
+	}
+	if err := checkAttr(gq.Children[0], "type.object.name"); err != nil {
+		t.Error(err)
+	}
+	if gq.Children[0].First != 0 {
+		t.Errorf("Expected count 0. Got: %v", gq.Children[0].First)
+	}
+	if err := checkAttr(gq.Children[1], "friends"); err != nil {
+		t.Error(err)
+	}
+	if gq.Children[1].First != 10 {
+		t.Errorf("Expected count 10. Got: %v", gq.Children[1].First)
+	}
+	if gq.Children[1].After != 3 {
+		t.Errorf("Expected after to be 3. Got: %v", gq.Children[1].Offset)
+	}
+}
+
+func TestParseOffset(t *testing.T) {
+	query := `
+	query {
+		user(_xid_: m.abcd) {
+			type.object.name
+			friends (first: 10, offset: 3) {
+			}
+		}
+	}`
+	gq, _, err := Parse(query)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	if gq == nil {
+		t.Error("subgraph is nil")
+		return
+	}
+	if len(gq.Children) != 2 {
+		t.Errorf("Expected 2 children. Got: %v", len(gq.Children))
+	}
+	if err := checkAttr(gq.Children[0], "type.object.name"); err != nil {
+		t.Error(err)
+	}
+	if gq.Children[0].First != 0 {
+		t.Errorf("Expected count 0. Got: %v", gq.Children[0].First)
+	}
+	if err := checkAttr(gq.Children[1], "friends"); err != nil {
+		t.Error(err)
+	}
+	if gq.Children[1].First != 10 {
+		t.Errorf("Expected count 10. Got: %v", gq.Children[1].First)
+	}
+	if gq.Children[1].Offset != 3 {
+		t.Errorf("Expected Offset 3. Got: %v", gq.Children[1].Offset)
+	}
+}
+
+func TestParseOffset_error(t *testing.T) {
+	query := `
+	query {
+		user(_xid_: m.abcd) {
+			type.object.name
+			friends (first: 10, offset: -3) {
+			}
+		}
+	}`
+	_, _, err := Parse(query)
+	if err == nil {
+		t.Error("Expected error on negative offset")
+		return
+	}
+}
+
 func TestParse_error2(t *testing.T) {
 	query := `
 		query {

posting/list.go

@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"log"
 	"math"
+	"sort"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -80,6 +81,12 @@ func NewList() *List {
 	return l
 }
 
+type ListOptions struct {
+	Offset   int
+	Count    int
+	AfterUid uint64
+}
+
 type ByUid []*types.Posting
 
 func (pa ByUid) Len() int           { return len(pa) }
@@ -674,35 +681,42 @@ func (l *List) LastCompactionTs() time.Time {
 	return l.lastCompact
 }
 
-func (l *List) GetUids(offset, count int) []uint64 {
+func (l *List) Uids(opt ListOptions) []uint64 {
 	l.wg.Wait()
 	l.RLock()
 	defer l.RUnlock()
 
-	if offset < 0 {
-		log.Fatalf("Unexpected offset: %v", offset)
+	if opt.Offset < 0 {
+		log.Fatalf("Unexpected offset: %v", opt.Offset)
 		return make([]uint64, 0)
 	}
 
-	if count < 0 {
-		count = 0 - count
-		offset = l.length() - count
+	var p types.Posting
+	if opt.AfterUid > 0 {
+		// sort.Search returns the index of the first element > AfterUid.
+		opt.Offset = sort.Search(l.length(), func(i int) bool {
+			l.get(&p, i)
+			return p.Uid() > opt.AfterUid
+		})
+	}
+	if opt.Count < 0 {
+		opt.Count = 0 - opt.Count
+		opt.Offset = l.length() - opt.Count
 	}
-	if offset < 0 {
-		offset = 0
+	if opt.Offset < 0 {
+		opt.Offset = 0
 	}
 
-	if count == 0 || count > l.length()-offset {
-		count = l.length() - offset
+	if opt.Count == 0 || opt.Count > l.length()-opt.Offset {
+		opt.Count = l.length() - opt.Offset
 	}
-	if count < 0 {
-		count = 0
+	if opt.Count < 0 {
+		opt.Count = 0
 	}
 
-	result := make([]uint64, count)
+	result := make([]uint64, opt.Count)
 	result = result[:0]
-	var p types.Posting
-	for i := offset; i < count+offset && i < l.length(); i++ {
+	for i := opt.Offset; i < opt.Count+opt.Offset && i < l.length(); i++ {
 		if ok := l.get(&p, i); !ok || p.Uid() == math.MaxUint64 {
 			break
 		}

posting/list_test.go

@@ -50,29 +50,58 @@ func checkUids(t *testing.T, l *List, uids ...uint64) error {
 		}
 	}
 	if len(uids) >= 3 {
-		ruids := l.GetUids(1, 2)
+		opts := ListOptions{1, 2, 0}
+		ruids := l.Uids(opts)
 		if len(ruids) != 2 {
 			return fmt.Errorf("Expected result of length: 2. Got: %v", len(ruids))
 		}
 
 		for i := 0; i < len(ruids); i++ {
 			if ruids[i] != uids[1+i] {
-				return fmt.Errorf("GetUids expected: %v. Got: %v", uids[1+i], ruids[i])
+				return fmt.Errorf("Uids expected: %v. Got: %v", uids[1+i], ruids[i])
 			}
 		}
 
-		ruids = l.GetUids(1, -2) // offset should be ignored.
+		opts = ListOptions{1, -2, 0}
+		ruids = l.Uids(opts) // offset should be ignored.
 		ulen := len(uids)
 		if ulen > 2 && len(ruids) != 2 {
 			return fmt.Errorf("Expected result of length: 2. Got: %v", len(ruids))
 		}
 
 		for i := 0; i < len(ruids); i++ {
 			if ruids[i] != uids[ulen-2+i] {
-				return fmt.Errorf("GetUids neg count expected: %v. Got: %v",
+				return fmt.Errorf("Uids neg count expected: %v. Got: %v",
 					uids[ulen-2+i], ruids[i])
 			}
 		}
+
+		// Tests for "after"
+		opts = ListOptions{0, 2, 10}
+		ruids = l.Uids(opts)
+		if len(ruids) != 2 {
+			return fmt.Errorf("Expected result of length: 2. Got: %v", len(ruids))
+		}
+		for i := 0; i < len(ruids); i++ {
+			if ruids[i] != uids[1+i] {
+				return fmt.Errorf("Uids expected: %v. Got: %v", uids[1+i], ruids[i])
+			}
+		}
+
+		opts = ListOptions{0, 2, 80}
+		ruids = l.Uids(opts)
+		if len(ruids) != 1 {
+			return fmt.Errorf("Expected result of length: 1. Got: %v", len(ruids))
+		}
+		if ruids[0] != 81 {
+			return fmt.Errorf("Uids expected: %v. Got: %v", uids[2], ruids[0])
+		}
+
+		opts = ListOptions{0, 2, 82}
+		ruids = l.Uids(opts)
+		if len(ruids) != 0 {
+			return fmt.Errorf("Expected result of length: 0. Got: %v", len(ruids))
+		}
 	}
 
 	return nil

query/query.go

@@ -112,6 +112,7 @@ type SubGraph struct {
 	Attr     string
 	Count    int
 	Offset   int
+	AfterUid uint64
 	Children []*SubGraph
 
 	Query  []byte
@@ -374,6 +375,8 @@ func treeCopy(gq *gql.GraphQuery, sg *SubGraph) {
 	for _, gchild := range gq.Children {
 		dst := new(SubGraph)
 		dst.Attr = gchild.Attr
+		dst.Offset = gchild.Offset
+		dst.AfterUid = gchild.After
 		dst.Count = gchild.First
 		sg.Children = append(sg.Children, dst)
 		treeCopy(gchild, dst)
@@ -460,6 +463,8 @@ func createTaskQuery(sg *SubGraph, sorted []uint64) []byte {
 	task.QueryAddAttr(b, ao)
 	task.QueryAddUids(b, vend)
 	task.QueryAddCount(b, int32(sg.Count))
+	task.QueryAddOffset(b, int32(sg.Offset))
+	task.QueryAddAfterUid(b, uint64(sg.AfterUid))
 
 	qend := task.QueryEnd(b)
 	b.Finish(qend)

task.fbs

@@ -5,6 +5,7 @@ table Query {
 	uids:[ulong];
 	count:int;
 	offset:int;
+	afterUid:ulong;
 }
 
 table Value {

task/Query.go

@@ -1,4 +1,4 @@
-// automatically generated, do not modify
+// automatically generated by the FlatBuffers compiler, do not modify
 
 package task
 
@@ -47,6 +47,10 @@ func (rcv *Query) Count() int32 {
 	return 0
 }
 
+func (rcv *Query) MutateCount(n int32) bool {
+	return rcv._tab.MutateInt32Slot(8, n)
+}
+
 func (rcv *Query) Offset() int32 {
 	o := flatbuffers.UOffsetT(rcv._tab.Offset(10))
 	if o != 0 {
@@ -55,11 +59,28 @@ func (rcv *Query) Offset() int32 {
 	return 0
 }
 
-func QueryStart(builder *flatbuffers.Builder) { builder.StartObject(4) }
+func (rcv *Query) MutateOffset(n int32) bool {
+	return rcv._tab.MutateInt32Slot(10, n)
+}
+
+func (rcv *Query) AfterUid() uint64 {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(12))
+	if o != 0 {
+		return rcv._tab.GetUint64(o + rcv._tab.Pos)
+	}
+	return 0
+}
+
+func (rcv *Query) MutateAfterUid(n uint64) bool {
+	return rcv._tab.MutateUint64Slot(12, n)
+}
+
+func QueryStart(builder *flatbuffers.Builder) { builder.StartObject(5) }
 func QueryAddAttr(builder *flatbuffers.Builder, attr flatbuffers.UOffsetT) { builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(attr), 0) }
 func QueryAddUids(builder *flatbuffers.Builder, uids flatbuffers.UOffsetT) { builder.PrependUOffsetTSlot(1, flatbuffers.UOffsetT(uids), 0) }
 func QueryStartUidsVector(builder *flatbuffers.Builder, numElems int) flatbuffers.UOffsetT { return builder.StartVector(8, numElems, 8)
 }
 func QueryAddCount(builder *flatbuffers.Builder, count int32) { builder.PrependInt32Slot(2, count, 0) }
 func QueryAddOffset(builder *flatbuffers.Builder, offset int32) { builder.PrependInt32Slot(3, offset, 0) }
+func QueryAddAfterUid(builder *flatbuffers.Builder, afterUid uint64) { builder.PrependUint64Slot(4, afterUid, 0) }
 func QueryEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT { return builder.EndObject() }

task/Result.go

@@ -1,4 +1,4 @@
-// automatically generated, do not modify
+// automatically generated by the FlatBuffers compiler, do not modify
 
 package task
 

task/UidList.go

@@ -1,4 +1,4 @@
-// automatically generated, do not modify
+// automatically generated by the FlatBuffers compiler, do not modify
 
 package task
 

task/Value.go

@@ -1,4 +1,4 @@
-// automatically generated, do not modify
+// automatically generated by the FlatBuffers compiler, do not modify
 
 package task
 

task/XidList.go

@@ -1,4 +1,4 @@
-// automatically generated, do not modify
+// automatically generated by the FlatBuffers compiler, do not modify
 
 package task