// 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
}
// processTask processes the query, accumulates and returns the result.
func processTask(q *task.Query) (*task.Result, error) {
attr := q.Attr
useFunc := len(q.SrcFunc) != 0
var n int
var tokens []string
var geoQuery *geo.QueryData
var err error
var intersectDest bool
var ineqValue types.Value
var ineqValueToken string
var isGeq, isLeq bool
if useFunc {
f := q.SrcFunc[0]
isGeq = f == "geq"
isLeq = f == "leq"
switch {
case isGeq:
fallthrough
case isLeq:
if len(q.SrcFunc) != 2 {
return nil, x.Errorf("Function requires 2 arguments, but got %d %v",
len(q.SrcFunc), q.SrcFunc)
}
ineqValue, err = getValue(attr, q.SrcFunc[1])
if err != nil {
return nil, err
}
// Tokenizing RHS value of inequality.
ineqTokens, err := posting.IndexTokens(attr, ineqValue)
if err != nil {
return nil, err
}
if len(ineqTokens) != 1 {
return nil, x.Errorf("Expected only 1 token but got: %v", ineqTokens)
}
ineqValueToken = ineqTokens[0]
// Get tokens geq / leq ineqValueToken.
tokens, err = getInequalityTokens(attr, ineqValueToken, isGeq)
if err != nil {
return nil, err
}
case geo.IsGeoFunc(q.SrcFunc[0]):
// For geo functions, we get extra information used for filtering.
tokens, geoQuery, err = geo.GetTokens(q.SrcFunc)
if err != nil {
return nil, err
}
default:
tokens, err = getTokens(q.SrcFunc)
if err != nil {
return nil, err
}
intersectDest = (strings.ToLower(q.SrcFunc[0]) == "allof")
}
n = len(tokens)
} else {
n = len(q.Uids)
}
var out task.Result
for i := 0; i < n; i++ {
var key []byte
if useFunc {
key = x.IndexKey(attr, tokens[i])
} else {
key = x.DataKey(attr, q.Uids[i])
}
// Get or create the posting list for an entity, attribute combination.
pl, decr := posting.GetOrCreate(key)
defer decr()
// If a posting list contains a value, we store that or else we store a nil
// byte so that processing is consistent later.
vbytes, vtype, err := pl.Value()
newValue := &task.Value{ValType: uint32(vtype)}
if err == nil {
newValue.Val = vbytes
} else {
newValue.Val = x.Nilbyte
}
out.Values = append(out.Values, newValue)
if q.DoCount {
out.Counts = append(out.Counts, uint32(pl.Length(0)))
// Add an empty UID list to make later processing consistent
out.UidMatrix = append(out.UidMatrix, &emptyUIDList)
continue
}
// The more usual case: Getting the UIDs.
opts := posting.ListOptions{
AfterUID: uint64(q.AfterUid),
}
// If we have srcFunc and Uids, it means its a filter. So we intersect.
if useFunc && len(q.Uids) > 0 {
opts.Intersect = &task.List{Uids: q.Uids}
}
out.UidMatrix = append(out.UidMatrix, pl.Uids(opts))
}
if (isGeq || isLeq) && len(tokens) > 0 && ineqValueToken == tokens[0] {
// Need to evaluate inequality for entries in the first bucket.
typ := schema.TypeOf(attr)
if typ == nil || !typ.IsScalar() {
return nil, x.Errorf("Attribute not scalar: %s %v", attr, typ)
}
scalarType := typ.(types.Scalar)
x.AssertTrue(len(out.UidMatrix) > 0)
// Filter the first row of UidMatrix. Since ineqValue != nil, we may
// assume that ineqValue is equal to the first token found in TokensTable.
algo.ApplyFilter(out.UidMatrix[0], func(uid uint64, i int) bool {
key := x.DataKey(attr, uid)
sv := getPostingValue(key, scalarType)
if sv == nil {
return false
}
if isGeq {
return !scalarType.Less(*sv, ineqValue)
}
return !scalarType.Less(ineqValue, *sv)
})
}
// If geo filter, do value check for correctness.
var values []*task.Value
if geoQuery != nil {
uids := algo.MergeSorted(out.UidMatrix)
for _, uid := range uids.Uids {
key := x.DataKey(attr, uid)
pl, decr := posting.GetOrCreate(key)
vbytes, vtype, err := pl.Value()
newValue := &task.Value{ValType: uint32(vtype)}
if err == nil {
newValue.Val = vbytes
} else {
newValue.Val = x.Nilbyte
}
values = append(values, newValue)
decr() // Decrement the reference count of the pl.
}
filtered := geo.FilterUids(uids, values, geoQuery)
for i := 0; i < len(out.UidMatrix); i++ {
out.UidMatrix[i] = algo.IntersectSorted([]*task.List{out.UidMatrix[i], filtered})
}
}
out.IntersectDest = intersectDest
return &out, nil
}