hdx/vendor/cloud.google.com/go/firestore/query_test.go

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// Copyright 2017 Google Inc. All Rights Reserved.
//
// 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 firestore
import (
"math"
"sort"
"testing"
"golang.org/x/net/context"
"cloud.google.com/go/internal/pretty"
pb "google.golang.org/genproto/googleapis/firestore/v1beta1"
tspb "github.com/golang/protobuf/ptypes/timestamp"
"github.com/golang/protobuf/ptypes/wrappers"
)
func TestFilterToProto(t *testing.T) {
for _, test := range []struct {
in filter
want *pb.StructuredQuery_Filter
}{
{
filter{[]string{"a"}, ">", 1},
&pb.StructuredQuery_Filter{FilterType: &pb.StructuredQuery_Filter_FieldFilter{
FieldFilter: &pb.StructuredQuery_FieldFilter{
Field: &pb.StructuredQuery_FieldReference{FieldPath: "a"},
Op: pb.StructuredQuery_FieldFilter_GREATER_THAN,
Value: intval(1),
},
}},
},
{
filter{[]string{"a"}, "==", nil},
&pb.StructuredQuery_Filter{FilterType: &pb.StructuredQuery_Filter_UnaryFilter{
UnaryFilter: &pb.StructuredQuery_UnaryFilter{
OperandType: &pb.StructuredQuery_UnaryFilter_Field{
Field: &pb.StructuredQuery_FieldReference{FieldPath: "a"},
},
Op: pb.StructuredQuery_UnaryFilter_IS_NULL,
},
}},
},
{
filter{[]string{"a"}, "==", math.NaN()},
&pb.StructuredQuery_Filter{FilterType: &pb.StructuredQuery_Filter_UnaryFilter{
UnaryFilter: &pb.StructuredQuery_UnaryFilter{
OperandType: &pb.StructuredQuery_UnaryFilter_Field{
Field: &pb.StructuredQuery_FieldReference{FieldPath: "a"},
},
Op: pb.StructuredQuery_UnaryFilter_IS_NAN,
},
}},
},
} {
got, err := test.in.toProto()
if err != nil {
t.Fatal(err)
}
if !testEqual(got, test.want) {
t.Errorf("%+v:\ngot\n%v\nwant\n%v", test.in, pretty.Value(got), pretty.Value(test.want))
}
}
}
func TestQueryToProto(t *testing.T) {
filtr := func(path []string, op string, val interface{}) *pb.StructuredQuery_Filter {
f, err := filter{path, op, val}.toProto()
if err != nil {
t.Fatal(err)
}
return f
}
c := &Client{projectID: "P", databaseID: "DB"}
coll := c.Collection("C")
q := coll.Query
type S struct {
A int `firestore:"a"`
}
docsnap := &DocumentSnapshot{
Ref: coll.Doc("D"),
proto: &pb.Document{
Fields: map[string]*pb.Value{"a": intval(7), "b": intval(8)},
},
}
for _, test := range []struct {
desc string
in Query
want *pb.StructuredQuery
}{
{
desc: "q.Select()",
in: q.Select(),
want: &pb.StructuredQuery{
Select: &pb.StructuredQuery_Projection{
Fields: []*pb.StructuredQuery_FieldReference{fref1("__name__")},
},
},
},
{
desc: `q.Select("a", "b")`,
in: q.Select("a", "b"),
want: &pb.StructuredQuery{
Select: &pb.StructuredQuery_Projection{
Fields: []*pb.StructuredQuery_FieldReference{fref1("a"), fref1("b")},
},
},
},
{
desc: `q.Select("a", "b").Select("c")`,
in: q.Select("a", "b").Select("c"), // last wins
want: &pb.StructuredQuery{
Select: &pb.StructuredQuery_Projection{
Fields: []*pb.StructuredQuery_FieldReference{fref1("c")},
},
},
},
{
desc: `q.SelectPaths([]string{"*"}, []string{"/"})`,
in: q.SelectPaths([]string{"*"}, []string{"/"}),
want: &pb.StructuredQuery{
Select: &pb.StructuredQuery_Projection{
Fields: []*pb.StructuredQuery_FieldReference{fref1("*"), fref1("/")},
},
},
},
{
desc: `q.Where("a", ">", 5)`,
in: q.Where("a", ">", 5),
want: &pb.StructuredQuery{Where: filtr([]string{"a"}, ">", 5)},
},
{
desc: `q.Where("a", "==", NaN)`,
in: q.Where("a", "==", float32(math.NaN())),
want: &pb.StructuredQuery{Where: filtr([]string{"a"}, "==", math.NaN())},
},
{
desc: `q.Where("a", ">", 5).Where("b", "<", "foo")`,
in: q.Where("a", ">", 5).Where("b", "<", "foo"),
want: &pb.StructuredQuery{
Where: &pb.StructuredQuery_Filter{
&pb.StructuredQuery_Filter_CompositeFilter{
&pb.StructuredQuery_CompositeFilter{
Op: pb.StructuredQuery_CompositeFilter_AND,
Filters: []*pb.StructuredQuery_Filter{
filtr([]string{"a"}, ">", 5), filtr([]string{"b"}, "<", "foo"),
},
},
},
},
},
},
{
desc: ` q.WherePath([]string{"/", "*"}, ">", 5)`,
in: q.WherePath([]string{"/", "*"}, ">", 5),
want: &pb.StructuredQuery{Where: filtr([]string{"/", "*"}, ">", 5)},
},
{
desc: `q.OrderBy("b", Asc).OrderBy("a", Desc).OrderByPath([]string{"~"}, Asc)`,
in: q.OrderBy("b", Asc).OrderBy("a", Desc).OrderByPath([]string{"~"}, Asc),
want: &pb.StructuredQuery{
OrderBy: []*pb.StructuredQuery_Order{
{fref1("b"), pb.StructuredQuery_ASCENDING},
{fref1("a"), pb.StructuredQuery_DESCENDING},
{fref1("~"), pb.StructuredQuery_ASCENDING},
},
},
},
{
desc: `q.Offset(2).Limit(3)`,
in: q.Offset(2).Limit(3),
want: &pb.StructuredQuery{
Offset: 2,
Limit: &wrappers.Int32Value{3},
},
},
{
desc: `q.Offset(2).Limit(3).Limit(4).Offset(5)`,
in: q.Offset(2).Limit(3).Limit(4).Offset(5), // last wins
want: &pb.StructuredQuery{
Offset: 5,
Limit: &wrappers.Int32Value{4},
},
},
{
desc: `q.OrderBy("a", Asc).StartAt(7).EndBefore(9)`,
in: q.OrderBy("a", Asc).StartAt(7).EndBefore(9),
want: &pb.StructuredQuery{
OrderBy: []*pb.StructuredQuery_Order{
{fref1("a"), pb.StructuredQuery_ASCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{intval(7)},
Before: true,
},
EndAt: &pb.Cursor{
Values: []*pb.Value{intval(9)},
Before: true,
},
},
},
{
desc: `q.OrderBy("a", Asc).StartAt(7).EndAt(9)`,
in: q.OrderBy("a", Asc).StartAt(7).EndAt(9),
want: &pb.StructuredQuery{
OrderBy: []*pb.StructuredQuery_Order{
{fref1("a"), pb.StructuredQuery_ASCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{intval(7)},
Before: true,
},
EndAt: &pb.Cursor{
Values: []*pb.Value{intval(9)},
Before: false,
},
},
},
{
desc: `q.OrderBy("a", Asc).StartAfter(7).EndAt(9)`,
in: q.OrderBy("a", Asc).StartAfter(7).EndAt(9),
want: &pb.StructuredQuery{
OrderBy: []*pb.StructuredQuery_Order{
{fref1("a"), pb.StructuredQuery_ASCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{intval(7)},
Before: false,
},
EndAt: &pb.Cursor{
Values: []*pb.Value{intval(9)},
Before: false,
},
},
},
{
desc: `q.OrderBy(DocumentID, Asc).StartAfter("foo").EndBefore("bar")`,
in: q.OrderBy(DocumentID, Asc).StartAfter("foo").EndBefore("bar"),
want: &pb.StructuredQuery{
OrderBy: []*pb.StructuredQuery_Order{
{fref1("__name__"), pb.StructuredQuery_ASCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{refval(coll.parentPath + "/documents/C/foo")},
Before: false,
},
EndAt: &pb.Cursor{
Values: []*pb.Value{refval(coll.parentPath + "/documents/C/bar")},
Before: true,
},
},
},
{
desc: `q.OrderBy("a", Asc).OrderBy("b", Desc).StartAfter(7, 8).EndAt(9, 10)`,
in: q.OrderBy("a", Asc).OrderBy("b", Desc).StartAfter(7, 8).EndAt(9, 10),
want: &pb.StructuredQuery{
OrderBy: []*pb.StructuredQuery_Order{
{fref1("a"), pb.StructuredQuery_ASCENDING},
{fref1("b"), pb.StructuredQuery_DESCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{intval(7), intval(8)},
Before: false,
},
EndAt: &pb.Cursor{
Values: []*pb.Value{intval(9), intval(10)},
Before: false,
},
},
},
{
// last of StartAt/After wins, same for End
desc: `q.OrderBy("a", Asc).StartAfter(1).StartAt(2).EndAt(3).EndBefore(4)`,
in: q.OrderBy("a", Asc).
StartAfter(1).StartAt(2).
EndAt(3).EndBefore(4),
want: &pb.StructuredQuery{
OrderBy: []*pb.StructuredQuery_Order{
{fref1("a"), pb.StructuredQuery_ASCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{intval(2)},
Before: true,
},
EndAt: &pb.Cursor{
Values: []*pb.Value{intval(4)},
Before: true,
},
},
},
// Start/End with DocumentSnapshot
// These tests are from the "Document Snapshot Cursors" doc.
{
desc: `q.StartAt(docsnap)`,
in: q.StartAt(docsnap),
want: &pb.StructuredQuery{
OrderBy: []*pb.StructuredQuery_Order{
{fref1("__name__"), pb.StructuredQuery_ASCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{refval(coll.parentPath + "/documents/C/D")},
Before: true,
},
},
},
{
desc: `q.OrderBy("a", Asc).StartAt(docsnap)`,
in: q.OrderBy("a", Asc).StartAt(docsnap),
want: &pb.StructuredQuery{
OrderBy: []*pb.StructuredQuery_Order{
{fref1("a"), pb.StructuredQuery_ASCENDING},
{fref1("__name__"), pb.StructuredQuery_ASCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{intval(7), refval(coll.parentPath + "/documents/C/D")},
Before: true,
},
},
},
{
desc: `q.OrderBy("a", Desc).StartAt(docsnap)`,
in: q.OrderBy("a", Desc).StartAt(docsnap),
want: &pb.StructuredQuery{
OrderBy: []*pb.StructuredQuery_Order{
{fref1("a"), pb.StructuredQuery_DESCENDING},
{fref1("__name__"), pb.StructuredQuery_DESCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{intval(7), refval(coll.parentPath + "/documents/C/D")},
Before: true,
},
},
},
{
desc: `q.OrderBy("a", Desc).OrderBy("b", Asc).StartAt(docsnap)`,
in: q.OrderBy("a", Desc).OrderBy("b", Asc).StartAt(docsnap),
want: &pb.StructuredQuery{
OrderBy: []*pb.StructuredQuery_Order{
{fref1("a"), pb.StructuredQuery_DESCENDING},
{fref1("b"), pb.StructuredQuery_ASCENDING},
{fref1("__name__"), pb.StructuredQuery_ASCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{intval(7), intval(8), refval(coll.parentPath + "/documents/C/D")},
Before: true,
},
},
},
{
desc: `q.Where("a", "==", 3).StartAt(docsnap)`,
in: q.Where("a", "==", 3).StartAt(docsnap),
want: &pb.StructuredQuery{
Where: filtr([]string{"a"}, "==", 3),
OrderBy: []*pb.StructuredQuery_Order{
{fref1("__name__"), pb.StructuredQuery_ASCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{refval(coll.parentPath + "/documents/C/D")},
Before: true,
},
},
},
{
desc: `q.Where("a", "<", 3).StartAt(docsnap)`,
in: q.Where("a", "<", 3).StartAt(docsnap),
want: &pb.StructuredQuery{
Where: filtr([]string{"a"}, "<", 3),
OrderBy: []*pb.StructuredQuery_Order{
{fref1("a"), pb.StructuredQuery_ASCENDING},
{fref1("__name__"), pb.StructuredQuery_ASCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{intval(7), refval(coll.parentPath + "/documents/C/D")},
Before: true,
},
},
},
{
desc: `q.Where("b", "==", 1).Where("a", "<", 3).StartAt(docsnap)`,
in: q.Where("b", "==", 1).Where("a", "<", 3).StartAt(docsnap),
want: &pb.StructuredQuery{
Where: &pb.StructuredQuery_Filter{
&pb.StructuredQuery_Filter_CompositeFilter{
&pb.StructuredQuery_CompositeFilter{
Op: pb.StructuredQuery_CompositeFilter_AND,
Filters: []*pb.StructuredQuery_Filter{
filtr([]string{"b"}, "==", 1),
filtr([]string{"a"}, "<", 3),
},
},
},
},
OrderBy: []*pb.StructuredQuery_Order{
{fref1("a"), pb.StructuredQuery_ASCENDING},
{fref1("__name__"), pb.StructuredQuery_ASCENDING},
},
StartAt: &pb.Cursor{
Values: []*pb.Value{intval(7), refval(coll.parentPath + "/documents/C/D")},
Before: true,
},
},
},
} {
got, err := test.in.toProto()
if err != nil {
t.Errorf("%s: %v", test.desc, err)
continue
}
test.want.From = []*pb.StructuredQuery_CollectionSelector{{CollectionId: "C"}}
if !testEqual(got, test.want) {
t.Errorf("%s:\ngot\n%v\nwant\n%v", test.desc, pretty.Value(got), pretty.Value(test.want))
}
}
}
func fref1(s string) *pb.StructuredQuery_FieldReference {
return fref([]string{s})
}
func TestQueryToProtoErrors(t *testing.T) {
st := map[string]interface{}{"a": ServerTimestamp}
del := map[string]interface{}{"a": Delete}
c := &Client{projectID: "P", databaseID: "DB"}
coll := c.Collection("C")
docsnap := &DocumentSnapshot{
Ref: coll.Doc("D"),
proto: &pb.Document{
Fields: map[string]*pb.Value{"a": intval(7)},
},
}
q := coll.Query
for _, query := range []Query{
Query{}, // no collection ID
q.Where("x", "!=", 1), // invalid operator
q.Where("~", ">", 1), // invalid path
q.WherePath([]string{"*", ""}, ">", 1), // invalid path
q.StartAt(1), // no OrderBy
q.StartAt(2).OrderBy("x", Asc).OrderBy("y", Desc), // wrong # OrderBy
q.Select("*"), // invalid path
q.SelectPaths([]string{"/", "", "~"}), // invalid path
q.OrderBy("[", Asc), // invalid path
q.OrderByPath([]string{""}, Desc), // invalid path
q.Where("x", "==", st), // ServerTimestamp in filter
q.OrderBy("a", Asc).StartAt(st), // ServerTimestamp in Start
q.OrderBy("a", Asc).EndAt(st), // ServerTimestamp in End
q.Where("x", "==", del), // Delete in filter
q.OrderBy("a", Asc).StartAt(del), // Delete in Start
q.OrderBy("a", Asc).EndAt(del), // Delete in End
q.OrderBy(DocumentID, Asc).StartAt(7), // wrong type for __name__
q.OrderBy(DocumentID, Asc).EndAt(7), // wrong type for __name__
q.OrderBy("b", Asc).StartAt(docsnap), // doc snapshot does not have order-by field
q.StartAt(docsnap).EndAt("x"), // mixed doc snapshot and fields
q.StartAfter("x").EndBefore(docsnap), // mixed doc snapshot and fields
} {
_, err := query.toProto()
if err == nil {
t.Errorf("%+v: got nil, want error", query)
}
}
}
func TestQueryMethodsDoNotModifyReceiver(t *testing.T) {
var empty Query
q := Query{}
_ = q.Select("a", "b")
if !testEqual(q, empty) {
t.Errorf("got %+v, want empty", q)
}
q = Query{}
q1 := q.Where("a", ">", 3)
if !testEqual(q, empty) {
t.Errorf("got %+v, want empty", q)
}
// Extra check because Where appends to a slice.
q1before := q.Where("a", ">", 3) // same as q1
_ = q1.Where("b", "<", "foo")
if !testEqual(q1, q1before) {
t.Errorf("got %+v, want %+v", q1, q1before)
}
q = Query{}
q1 = q.OrderBy("a", Asc)
if !testEqual(q, empty) {
t.Errorf("got %+v, want empty", q)
}
// Extra check because Where appends to a slice.
q1before = q.OrderBy("a", Asc) // same as q1
_ = q1.OrderBy("b", Desc)
if !testEqual(q1, q1before) {
t.Errorf("got %+v, want %+v", q1, q1before)
}
q = Query{}
_ = q.Offset(5)
if !testEqual(q, empty) {
t.Errorf("got %+v, want empty", q)
}
q = Query{}
_ = q.Limit(5)
if !testEqual(q, empty) {
t.Errorf("got %+v, want empty", q)
}
q = Query{}
_ = q.StartAt(5)
if !testEqual(q, empty) {
t.Errorf("got %+v, want empty", q)
}
q = Query{}
_ = q.StartAfter(5)
if !testEqual(q, empty) {
t.Errorf("got %+v, want empty", q)
}
q = Query{}
_ = q.EndAt(5)
if !testEqual(q, empty) {
t.Errorf("got %+v, want empty", q)
}
q = Query{}
_ = q.EndBefore(5)
if !testEqual(q, empty) {
t.Errorf("got %+v, want empty", q)
}
}
func TestQueryFromCollectionRef(t *testing.T) {
c := &Client{}
coll := c.Collection("C")
got := coll.Select("x").Offset(8)
want := Query{
c: c,
parentPath: c.path(),
collectionID: "C",
selection: []FieldPath{{"x"}},
offset: 8,
}
if !testEqual(got, want) {
t.Fatalf("got %+v, want %+v", got, want)
}
}
func TestQueryGetAll(t *testing.T) {
// This implicitly tests DocumentIterator as well.
const dbPath = "projects/projectID/databases/(default)"
ctx := context.Background()
c, srv := newMock(t)
docNames := []string{"C/a", "C/b"}
wantPBDocs := []*pb.Document{
{
Name: dbPath + "/documents/" + docNames[0],
CreateTime: aTimestamp,
UpdateTime: aTimestamp,
Fields: map[string]*pb.Value{"f": intval(2)},
},
{
Name: dbPath + "/documents/" + docNames[1],
CreateTime: aTimestamp2,
UpdateTime: aTimestamp3,
Fields: map[string]*pb.Value{"f": intval(1)},
},
}
wantReadTimes := []*tspb.Timestamp{aTimestamp, aTimestamp2}
srv.addRPC(nil, []interface{}{
&pb.RunQueryResponse{Document: wantPBDocs[0], ReadTime: aTimestamp},
&pb.RunQueryResponse{Document: wantPBDocs[1], ReadTime: aTimestamp2},
})
gotDocs, err := c.Collection("C").Documents(ctx).GetAll()
if err != nil {
t.Fatal(err)
}
if got, want := len(gotDocs), len(wantPBDocs); got != want {
t.Errorf("got %d docs, wanted %d", got, want)
}
for i, got := range gotDocs {
want, err := newDocumentSnapshot(c.Doc(docNames[i]), wantPBDocs[i], c, wantReadTimes[i])
if err != nil {
t.Fatal(err)
}
if !testEqual(got, want) {
// avoid writing a cycle
got.c = nil
want.c = nil
t.Errorf("#%d: got %+v, want %+v", i, pretty.Value(got), pretty.Value(want))
}
}
}
func TestQueryCompareFunc(t *testing.T) {
mv := func(fields ...interface{}) map[string]*pb.Value {
m := map[string]*pb.Value{}
for i := 0; i < len(fields); i += 2 {
m[fields[i].(string)] = fields[i+1].(*pb.Value)
}
return m
}
snap := func(ref *DocumentRef, fields map[string]*pb.Value) *DocumentSnapshot {
return &DocumentSnapshot{Ref: ref, proto: &pb.Document{Fields: fields}}
}
c := &Client{}
coll := c.Collection("C")
doc1 := coll.Doc("doc1")
doc2 := coll.Doc("doc2")
doc3 := coll.Doc("doc3")
doc4 := coll.Doc("doc4")
for _, test := range []struct {
q Query
in []*DocumentSnapshot
want []*DocumentSnapshot
}{
{
q: coll.OrderBy("foo", Asc),
in: []*DocumentSnapshot{
snap(doc3, mv("foo", intval(2))),
snap(doc4, mv("foo", intval(1))),
snap(doc2, mv("foo", intval(2))),
},
want: []*DocumentSnapshot{
snap(doc4, mv("foo", intval(1))),
snap(doc2, mv("foo", intval(2))),
snap(doc3, mv("foo", intval(2))),
},
},
{
q: coll.OrderBy("foo", Desc),
in: []*DocumentSnapshot{
snap(doc3, mv("foo", intval(2))),
snap(doc4, mv("foo", intval(1))),
snap(doc2, mv("foo", intval(2))),
},
want: []*DocumentSnapshot{
snap(doc3, mv("foo", intval(2))),
snap(doc2, mv("foo", intval(2))),
snap(doc4, mv("foo", intval(1))),
},
},
{
q: coll.OrderBy("foo.bar", Asc),
in: []*DocumentSnapshot{
snap(doc1, mv("foo", mapval(mv("bar", intval(1))))),
snap(doc2, mv("foo", mapval(mv("bar", intval(2))))),
snap(doc3, mv("foo", mapval(mv("bar", intval(2))))),
},
want: []*DocumentSnapshot{
snap(doc1, mv("foo", mapval(mv("bar", intval(1))))),
snap(doc2, mv("foo", mapval(mv("bar", intval(2))))),
snap(doc3, mv("foo", mapval(mv("bar", intval(2))))),
},
},
{
q: coll.OrderBy("foo.bar", Desc),
in: []*DocumentSnapshot{
snap(doc1, mv("foo", mapval(mv("bar", intval(1))))),
snap(doc2, mv("foo", mapval(mv("bar", intval(2))))),
snap(doc3, mv("foo", mapval(mv("bar", intval(2))))),
},
want: []*DocumentSnapshot{
snap(doc3, mv("foo", mapval(mv("bar", intval(2))))),
snap(doc2, mv("foo", mapval(mv("bar", intval(2))))),
snap(doc1, mv("foo", mapval(mv("bar", intval(1))))),
},
},
} {
got := append([]*DocumentSnapshot(nil), test.in...)
sort.Sort(byQuery{test.q.compareFunc(), got})
if diff := testDiff(got, test.want); diff != "" {
t.Errorf("%+v: %s", test.q, diff)
}
}
// Want error on missing field.
q := coll.OrderBy("bar", Asc)
if q.err != nil {
t.Fatalf("bad query: %v", q.err)
}
cf := q.compareFunc()
s := snap(doc1, mv("foo", intval(1)))
if _, err := cf(s, s); err == nil {
t.Error("got nil, want error")
}
}
type byQuery struct {
compare func(d1, d2 *DocumentSnapshot) (int, error)
docs []*DocumentSnapshot
}
func (b byQuery) Len() int { return len(b.docs) }
func (b byQuery) Swap(i, j int) { b.docs[i], b.docs[j] = b.docs[j], b.docs[i] }
func (b byQuery) Less(i, j int) bool {
c, err := b.compare(b.docs[i], b.docs[j])
if err != nil {
panic(err)
}
return c < 0
}