// applyOrderAndPagination orders each posting list by a given attribute
// before applying pagination.
func (sg *SubGraph) applyOrderAndPagination(ctx context.Context) error {
if len(sg.Params.Order) == 0 {
return nil
}
if sg.Params.Count == 0 {
// Only retrieve up to 1000 results by default.
sg.Params.Count = 1000
}
sort := &task.Sort{
Attr: sg.Params.Order,
UidMatrix: sg.uidMatrix,
Offset: int32(sg.Params.Offset),
Count: int32(sg.Params.Count),
Desc: sg.Params.OrderDesc,
}
result, err := worker.SortOverNetwork(ctx, sort)
if err != nil {
return err
}
x.AssertTrue(len(result.UidMatrix) == len(sg.uidMatrix))
sg.uidMatrix = result.GetUidMatrix()
// Update sg.destUID. Iterate over the UID matrix (which is not sorted by
// UID). For each element in UID matrix, we do a binary search in the
// current destUID and mark it. Then we scan over this bool array and
// rebuild destUIDs.
included := make([]bool, len(sg.DestUIDs.Uids))
for _, ul := range sg.uidMatrix {
for _, uid := range ul.Uids {
idx := algo.IndexOf(sg.DestUIDs, uid) // Binary search.
if idx >= 0 {
included[idx] = true
}
}
}
algo.ApplyFilter(sg.DestUIDs,
func(uid uint64, idx int) bool { return included[idx] })
return nil
}
// This method gets the values and children for a subgraph.
func (sg *SubGraph) preTraverse(uid uint64, dst outputNode) error {
invalidUids := make(map[uint64]bool)
// We go through all predicate children of the subgraph.
for _, pc := range sg.Children {
idx := algo.IndexOf(pc.SrcUIDs, uid)
if idx < 0 {
continue
}
ul := pc.uidMatrix[idx]
fieldName := pc.Attr
if pc.Params.Alias != "" {
fieldName = pc.Params.Alias
}
if sg.Params.GetUID || sg.Params.isDebug {
dst.SetUID(uid)
}
if len(pc.counts) > 0 {
c := types.Int32(pc.counts[idx])
uc := dst.New(fieldName)
uc.AddValue("_count_", &c)
dst.AddChild(fieldName, uc)
} else if len(ul.Uids) > 0 || len(pc.Children) > 0 {
// We create as many predicate entity children as the length of uids for
// this predicate.
for _, childUID := range ul.Uids {
if invalidUids[childUID] {
continue
}
uc := dst.New(fieldName)
// Doing check for UID here is no good because some of these might be
// invalid nodes.
// if pc.Params.GetUID || pc.Params.isDebug {
// dst.SetUID(uid)
// }
if rerr := pc.preTraverse(childUID, uc); rerr != nil {
if rerr.Error() == "_INV_" {
invalidUids[childUID] = true
continue // next UID.
}
// Some other error.
log.Printf("Error while traversal: %v", rerr)
return rerr
}
if !uc.IsEmpty() {
dst.AddChild(fieldName, uc)
}
}
} else {
tv := pc.values[idx]
v, err := getValue(tv)
if err != nil {
return err
}
if pc.Attr == "_xid_" {
txt, err := v.MarshalText()
if err != nil {
return err
}
dst.SetXID(string(txt))
} else {
globalType := schema.TypeOf(pc.Attr)
schemaType := pc.Params.AttrType
sv := v
if schemaType != nil {
// Do type checking on response values
if !schemaType.IsScalar() {
return x.Errorf("Unknown Scalar:%v. Leaf predicate:'%v' must be"+
" one of the scalar types defined in the schema.", pc.Params.AttrType, pc.Attr)
}
st := schemaType.(types.Scalar)
// Convert to schema type.
sv, err = st.Convert(v)
if bytes.Equal(tv.Val, nil) || err != nil {
// skip values that don't convert.
return x.Errorf("_INV_")
}
} else if globalType != nil {
// Try to coerce types if this is an optional scalar outside an
// object definition.
if !globalType.IsScalar() {
return x.Errorf("Leaf predicate:'%v' must be a scalar.", pc.Attr)
}
gt := globalType.(types.Scalar)
// Convert to schema type.
sv, err = gt.Convert(v)
if bytes.Equal(tv.Val, nil) || err != nil {
continue
}
}
if bytes.Equal(tv.Val, nil) {
continue
}
dst.AddValue(fieldName, sv)
}
}
}
return nil
}