Add transaction buffer filter.

filter/txnBuf/txnbuf_test.go

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package txnBuf
+
+import (
+        "bytes"
+        "fmt"
+        "math/rand"
+        "testing"
+
+        "github.com/luci/gae/filter/count"
+        "github.com/luci/gae/impl/memory"
+        "github.com/luci/gae/service/datastore"
+        "github.com/luci/luci-go/common/cmpbin"
+        "github.com/luci/luci-go/common/errors"
+        . "github.com/luci/luci-go/common/testing/assertions"
+        . "github.com/smartystreets/goconvey/convey"
+        "golang.org/x/net/context"
+)
+
+type Foo struct {
+        ID     int64          `gae:"$id"`
+        Parent *datastore.Key `gae:"$parent"`
+
+        Value   []int64
+        ValueNI []byte `gae:",noindex"`
+        Sort    []string
+}
+
+func toIntSlice(stuff []interface{}) []int64 {
+        vals, ok := stuff[0].([]int64)
+        if !ok {
+                vals = make([]int64, len(stuff))
+                for i := range vals {
+                        vals[i] = int64(stuff[i].(int))
+                }
+        }
+        return vals
+}
+
+func toInt64(thing interface{}) int64 {
+        switch x := thing.(type) {
+        case int:
+                return int64(x)
+        case int64:
+                return x
+        default:
+                panic(fmt.Errorf("wat r it? %v", x))
+        }
+}
+
+func fooShouldHave(ds datastore.Interface) func(interface{}, ...interface{}) string {
+        return func(id interface{}, values ...interface{}) string {
+                f := &Foo{ID: toInt64(id)}
+                err := ds.Get(f)
+                if len(values) == 0 {
+                        return ShouldEqual(err, datastore.ErrNoSuchEntity)
+                }
+
+                ret := ShouldBeNil(err)
+                if ret == "" {
+                        if data, ok := values[0].([]byte); ok {
+                                ret = ShouldResemble(f.ValueNI, data)
+                        } else {
+                                ret = ShouldResemble(f.Value, toIntSlice(values))
+                        }
+                }
+                return ret
+        }
+}
+
+func fooSetTo(ds datastore.Interface) func(interface{}, ...interface{}) string {
+        return func(id interface{}, values ...interface{}) string {
+                f := &Foo{ID: toInt64(id)}
+                if len(values) == 0 {
+                        return ShouldBeNil(ds.Delete(ds.KeyForObj(f)))
+                }
+                if data, ok := values[0].([]byte); ok {
+                        f.ValueNI = data
+                } else {
+                        f.Value = toIntSlice(values)
+                }
+                return ShouldBeNil(ds.Put(f))
+        }
+}
+
+func TestTransactionBuffers(t *testing.T) {
+        t.Parallel()
+
+        cb := func(i int64) string {
+                buf := &bytes.Buffer{}
+                cmpbin.WriteInt(buf, i)
+                return buf.String()
+        }
+
+        rs := rand.NewSource(0)
+        dataMultiRoot := make([]*Foo, 20)
+        dataSingleRoot := make([]*Foo, 20)
+        root := datastore.MakeKey("dev~app", "", "Parent", 1)
+        nums := make([]string, 20)
+        for i := range dataMultiRoot {
+                id := int64(i + 1)
+                nums[i] = cb(id)
+
+                val := make([]int64, rs.Int63()%20)
+                for j := range val {
+                        r := rs.Int63()
+                        val[j] = r
+                }
+
+                dataMultiRoot[i] = &Foo{ID: id, Value: val}
+                dataSingleRoot[i] = &Foo{ID: id, Parent: root, Value: val}
+        }
+
+        hugeField := make([]byte, DefaultSizeBudget/8)
+        for i := range hugeField {
+                hugeField[i] = byte(i)
+        }
+
+        hugeData := make([]*Foo, 11)
+        for i := range hugeData {
+                hugeData[i] = &Foo{ID: int64(i + 1), ValueNI: hugeField}
+        }
+
+        mkds := func(data []*Foo) (under, over *count.DSCounter, ds datastore.Interface) {
+                c := memory.Use(context.Background())
+                ds = datastore.Get(c)
+                _, err := ds.AllocateIDs(ds.KeyForObj(data[0]), 100)
+                if err != nil {
+                        panic(err)
+                }
+                if err := ds.PutMulti(data); err != nil {
+                        panic(err)
+                }
+
+                c, under = count.FilterRDS(c)
+                c = FilterRDS(c)
+                c, over = count.FilterRDS(c)
+                ds = datastore.Get(c)
+                return
+        }
+
+        Convey("Get/Put/Delete", t, func() {
+                under, over, ds := mkds(dataMultiRoot)
+
+                So(under.PutMulti.Total(), ShouldEqual, 0)
+                So(over.PutMulti.Total(), ShouldEqual, 0)
+
+                Convey("Good", func() {
+                        Convey("read-only", func() {
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        So(4, fooShouldHave(ds), dataMultiRoot[3].Value)
+                                        return nil
+                                }, nil), ShouldBeNil)
+                        })
+
+                        Convey("single-level read/write", func() {
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        So(4, fooShouldHave(ds), dataMultiRoot[3].Value)
+
+                                        So(4, fooSetTo(ds), 1, 2, 3, 4)
+
+                                        So(3, fooSetTo(ds), 1, 2, 3, 4)
+
+                                        // look! it remembers :)
+                                        So(4, fooShouldHave(ds), 1, 2, 3, 4)
+                                        return nil
+                                }, &datastore.TransactionOptions{XG: true}), ShouldBeNil)
+
+                                So(under.PutMulti.Total(), ShouldEqual, 1)
+
+                                So(3, fooShouldHave(ds), 1, 2, 3, 4)
+                                So(4, fooShouldHave(ds), 1, 2, 3, 4)
+                        })
+
+                        Convey("multi-level read/write", func() {
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        So(3, fooShouldHave(ds), dataMultiRoot[2].Value)
+
+                                        So(3, fooSetTo(ds), 1, 2, 3, 4)
+                                        So(7, fooSetTo(ds))
+
+                                        // inner, failing, transaction
+                                        So(ds.RunInTransaction(func(c context.Context) error {
+                                                ds := datastore.Get(c)
+
+                                                // we can see stuff written in the outer txn
+                                                So(7, fooShouldHave(ds))
+                                                So(3, fooShouldHave(ds), 1, 2, 3, 4)
+
+                                                So(3, fooSetTo(ds), 10, 20, 30, 40)
+
+                                                // disaster strikes!
+                                                return errors.New("whaaaa")
+                                        }, nil), ShouldErrLike, "whaaaa")
+
+                                        So(3, fooShouldHave(ds), 1, 2, 3, 4)
+
+                                        // inner, successful, transaction
+                                        So(ds.RunInTransaction(func(c context.Context) error {
+                                                ds := datastore.Get(c)
+                                                So(3, fooShouldHave(ds), 1, 2, 3, 4)
+                                                So(3, fooSetTo(ds), 10, 20, 30, 40)
+                                                return nil
+                                        }, nil), ShouldBeNil)
+
+                                        // now we see it
+                                        So(3, fooShouldHave(ds), 10, 20, 30, 40)
+                                        return nil
+                                }, &datastore.TransactionOptions{XG: true}), ShouldBeNil)
+
+                                So(under.PutMulti.Total(), ShouldEqual, 1)
+                                So(under.DeleteMulti.Total(), ShouldEqual, 1)
+
+                                // 'over' Put operations are amplified because the inner transaction
+                                // commits go through the 'over' filter on the outer transaction. So it's
+                                // # Puts + # inner txns.
+                                So(over.PutMulti.Total(), ShouldEqual, 5)
+
+                                So(7, fooShouldHave(ds))
+                                So(3, fooShouldHave(ds), 10, 20, 30, 40)
+                        })
+
+                        Convey("can allocate IDs from an inner transaction", func() {
+                                nums := []int64{4, 8, 15, 16, 23, 42}
+                                k := (*datastore.Key)(nil)
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        So(ds.RunInTransaction(func(c context.Context) error {
+                                                ds := datastore.Get(c)
+                                                f := &Foo{Value: nums}
+                                                So(ds.Put(f), ShouldBeNil)
+                                                k = ds.KeyForObj(f)
+                                                return nil
+                                        }, nil), ShouldBeNil)
+
+                                        So(k.IntID(), fooShouldHave(ds), nums)
+
+                                        return nil
+                                }, nil), ShouldBeNil)
+
+                                So(k.IntID(), fooShouldHave(ds), nums)
+                        })
+
+                        Convey("inner txn too big allows outer txn", func() {
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        So(18, fooSetTo(ds), hugeField)
+
+                                        So(ds.RunInTransaction(func(c context.Context) error {
+                                                ds := datastore.Get(c)
+                                                So(ds.PutMulti(hugeData), ShouldBeNil)
+                                                return nil
+                                        }, nil), ShouldErrLike, ErrTransactionTooLarge)
+
+                                        return nil
+                                }, &datastore.TransactionOptions{XG: true}), ShouldBeNil)
+
+                                So(18, fooShouldHave(ds), hugeField)
+                        })
+
+                        Convey("outer txn too big prevents inner txn", func() {
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        So(ds.PutMulti(hugeData), ShouldBeNil)
+
+                                        So(ds.RunInTransaction(func(c context.Context) error {
+                                                panic("never!")
+                                        }, nil), ShouldErrLike, ErrTransactionTooLarge)
+
+                                        return nil
+                                }, &datastore.TransactionOptions{XG: true}), ShouldBeNil)
+
+                                So(1, fooShouldHave(ds), hugeField)
+                        })
+
+                })
+
+                Convey("Bad", func() {
+
+                        Convey("too many roots", func() {
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        f := &Foo{ID: 7}
+                                        So(ds.Get(f), ShouldBeNil)
+                                        So(f, ShouldResemble, dataMultiRoot[6])
+
+                                        So(ds.RunInTransaction(func(c context.Context) error {
+                                                return datastore.Get(c).Get(&Foo{ID: 6})
+                                        }, nil), ShouldErrLike, "too many entity groups")
+
+                                        f.Value = []int64{9}
+                                        So(ds.Put(f), ShouldBeNil)
+
+                                        return nil
+                                }, nil), ShouldBeNil)
+
+                                f := &Foo{ID: 7}
+                                So(ds.Get(f), ShouldBeNil)
+                                So(f.Value, ShouldResemble, []int64{9})
+                        })
+
+                        Convey("buffered errors never reach the datastore", func() {
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        So(ds.Put(&Foo{ID: 1, Value: []int64{1, 2, 3, 4}}), ShouldBeNil)
+                                        return errors.New("boop")
+                                }, nil), ShouldErrLike, "boop")
+                                So(under.PutMulti.Total(), ShouldEqual, 0)
+                                So(over.PutMulti.Successes(), ShouldEqual, 1)
+                        })
+
+                })
+
+        })
+
+        Convey("Queries", t, func() {
+                Convey("Good", func() {
+                        q := datastore.NewQuery("Foo").Ancestor(root)
+
+                        Convey("normal", func() {
+                                _, _, ds := mkds(dataSingleRoot)
+                                ds.Testable().AddIndexes(&datastore.IndexDefinition{
+                                        Kind:     "Foo",
+                                        Ancestor: true,
+                                        SortBy: []datastore.IndexColumn{
+                                                {Property: "Value"},
+                                        },
+                                })
+
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        q = q.Lt("Value", 400000000000000000)
+
+                                        vals := []*Foo{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 8)
+
+                                        f := &Foo{ID: 1, Parent: root}
+                                        So(ds.Get(f), ShouldBeNil)
+                                        f.Value = append(f.Value, 100)
+                                        So(ds.Put(f), ShouldBeNil)
+
+                                        // Wowee, zowee, merged queries!
+                                        vals2 := []*Foo{}
+                                        So(ds.GetAll(q, &vals2), ShouldBeNil)
+                                        So(len(vals2), ShouldEqual, 9)
+                                        So(vals2[0], ShouldResemble, f)
+
+                                        vals2 = []*Foo{}
+                                        So(ds.GetAll(q.Limit(2).Offset(1), &vals2), ShouldBeNil)
+                                        So(len(vals2), ShouldEqual, 2)
+                                        So(vals2, ShouldResemble, vals[:2])
+
+                                        return nil
+                                }, nil), ShouldBeNil)
+                        })
+
+                        Convey("keysOnly", func() {
+                                _, _, ds := mkds([]*Foo{
+                                        {ID: 2, Parent: root, Value: []int64{1, 2, 3, 4, 5, 6, 7}},
+                                        {ID: 3, Parent: root, Value: []int64{3, 4, 5, 6, 7, 8, 9}},
+                                        {ID: 4, Parent: root, Value: []int64{3, 5, 7, 9, 11, 100, 1}},
+                                        {ID: 5, Parent: root, Value: []int64{1, 70, 101}},
+                                })
+
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        q = q.Eq("Value", 1).KeysOnly(true)
+                                        vals := []*datastore.Key{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 3)
+                                        So(vals[2], ShouldResemble, ds.MakeKey("Parent", 1, "Foo", 5))
+
+                                        // can remove keys
+                                        So(ds.Delete(ds.MakeKey("Parent", 1, "Foo", 2)), ShouldBeNil)
+                                        vals = []*datastore.Key{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 2)
+
+                                        // and add new ones
+                                        So(ds.Put(&Foo{ID: 1, Parent: root, Value: []int64{1, 7, 100}}), ShouldBeNil)
+                                        So(ds.Put(&Foo{ID: 7, Parent: root, Value: []int64{20, 1}}), ShouldBeNil)
+                                        vals = []*datastore.Key{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 4)
+
+                                        So(vals[0].IntID(), ShouldEqual, 1)
+                                        So(vals[1].IntID(), ShouldEqual, 4)
+                                        So(vals[2].IntID(), ShouldEqual, 5)
+                                        So(vals[3].IntID(), ShouldEqual, 7)
+
+                                        return nil
+                                }, nil), ShouldBeNil)
+                        })
+
+                        Convey("project", func() {
+                                _, _, ds := mkds([]*Foo{
+                                        {ID: 2, Parent: root, Value: []int64{1, 2, 3, 4, 5, 6, 7}},
+                                        {ID: 3, Parent: root, Value: []int64{3, 4, 5, 6, 7, 8, 9}},
+                                        {ID: 4, Parent: root, Value: []int64{3, 5, 7, 9, 11, 100, 1}},
+                                        {ID: 5, Parent: root, Value: []int64{1, 70, 101}},
+                                })
+
+                                ds.Testable().AddIndexes(&datastore.IndexDefinition{
+                                        Kind:     "Foo",
+                                        Ancestor: true,
+                                        SortBy: []datastore.IndexColumn{
+                                                {Property: "Value"},
+                                        },
+                                })
+
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        q = q.Project("Value").Offset(4).Limit(10)
+
+                                        vals := []datastore.PropertyMap{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 10)
+
+                                        expect := []struct {
+                                                id  int64
+                                                val int64
+                                        }{
+                                                {2, 3},
+                                                {3, 3},
+                                                {4, 3},
+                                                {2, 4},
+                                                {3, 4},
+                                                {2, 5},
+                                                {3, 5},
+                                                {4, 5},
+                                                {2, 6},
+                                                {3, 6},
+                                        }
+
+                                        for i, pm := range vals {
+                                                So(pm.GetMetaDefault("key", nil), ShouldResemble, ds.MakeKey("Parent", 1, "Foo", expect[i].id))
+                                                So(pm["Value"][0].Value(), ShouldEqual, expect[i].val)
+                                        }
+
+                                        // should remove 4 entries, but there are plenty more to fill
+                                        So(ds.Delete(ds.MakeKey("Parent", 1, "Foo", 2)), ShouldBeNil)
+
+                                        vals = []datastore.PropertyMap{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 10)
+
+                                        expect = []struct {
+                                                id  int64
+                                                val int64
+                                        }{
+                                                // note (3, 3) and (4, 3) are correctly missing because deleting
+                                                // 2 removed two entries which are hidden by the Offset(4).
+                                                {3, 4},
+                                                {3, 5},
+                                                {4, 5},
+                                                {3, 6},
+                                                {3, 7},
+                                                {4, 7},
+                                                {3, 8},
+                                                {3, 9},
+                                                {4, 9},
+                                                {4, 11},
+                                        }
+
+                                        for i, pm := range vals {
+                                                So(pm.GetMetaDefault("key", nil), ShouldResemble, ds.MakeKey("Parent", 1, "Foo", expect[i].id))
+                                                So(pm["Value"][0].Value(), ShouldEqual, expect[i].val)
+                                        }
+
+                                        So(ds.Put(&Foo{ID: 1, Parent: root, Value: []int64{3, 9}}), ShouldBeNil)
+
+                                        vals = []datastore.PropertyMap{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 10)
+
+                                        expect = []struct {
+                                                id  int64
+                                                val int64
+                                        }{
+                                                // 'invisible' {1, 3} entry bumps the {4, 3} into view.
+                                                {4, 3},
+                                                {3, 4},
+                                                {3, 5},
+                                                {4, 5},
+                                                {3, 6},
+                                                {3, 7},
+                                                {4, 7},
+                                                {3, 8},
+                                                {1, 9},
+                                                {3, 9},
+                                                {4, 9},
+                                        }
+
+                                        for i, pm := range vals {
+                                                So(pm.GetMetaDefault("key", nil), ShouldResemble, ds.MakeKey("Parent", 1, "Foo", expect[i].id))
+                                                So(pm["Value"][0].Value(), ShouldEqual, expect[i].val)
+                                        }
+
+                                        return nil
+                                }, nil), ShouldBeNil)
+
+                        })
+
+                        Convey("project+distinct", func() {
+                                _, _, ds := mkds([]*Foo{
+                                        {ID: 2, Parent: root, Value: []int64{1, 2, 3, 4, 5, 6, 7}},
+                                        {ID: 3, Parent: root, Value: []int64{3, 4, 5, 6, 7, 8, 9}},
+                                        {ID: 4, Parent: root, Value: []int64{3, 5, 7, 9, 11, 100, 1}},
+                                        {ID: 5, Parent: root, Value: []int64{1, 70, 101}},
+                                })
+
+                                ds.Testable().AddIndexes(&datastore.IndexDefinition{
+                                        Kind:     "Foo",
+                                        Ancestor: true,
+                                        SortBy: []datastore.IndexColumn{
+                                                {Property: "Value"},
+                                        },
+                                })
+
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        q = q.Project("Value").Distinct(true)
+
+                                        vals := []datastore.PropertyMap{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 13)
+
+                                        expect := []struct {
+                                                id  int64
+                                                val int64
+                                        }{
+                                                {2, 1},
+                                                {2, 2},
+                                                {2, 3},
+                                                {2, 4},
+                                                {2, 5},
+                                                {2, 6},
+                                                {2, 7},
+                                                {3, 8},
+                                                {3, 9},
+                                                {4, 11},
+                                                {5, 70},
+                                                {4, 100},
+                                                {5, 101},
+                                        }
+
+                                        for i, pm := range vals {
+                                                So(pm["Value"][0].Value(), ShouldEqual, expect[i].val)
+                                                So(pm.GetMetaDefault("key", nil), ShouldResemble, ds.MakeKey("Parent", 1, "Foo", expect[i].id))
+                                        }
+
+                                        return nil
+                                }, nil), ShouldBeNil)
+                        })
+
+                        Convey("overwrite", func() {
+                                data := []*Foo{
+                                        {ID: 2, Parent: root, Value: []int64{1, 2, 3, 4, 5, 6, 7}},
+                                        {ID: 3, Parent: root, Value: []int64{3, 4, 5, 6, 7, 8, 9}},
+                                        {ID: 4, Parent: root, Value: []int64{3, 5, 7, 9, 11, 100, 1, 2}},
+                                        {ID: 5, Parent: root, Value: []int64{1, 70, 101}},
+                                }
+
+                                _, _, ds := mkds(data)
+
+                                q = q.Eq("Value", 2, 3)
+
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        vals := []*Foo{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 2)
+
+                                        So(vals[0], ShouldResemble, data[0])
+                                        So(vals[1], ShouldResemble, data[2])
+
+                                        foo2 := &Foo{ID: 2, Parent: root, Value: []int64{2, 3}}
+                                        So(ds.Put(foo2), ShouldBeNil)
+
+                                        vals = []*Foo{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 2)
+
+                                        So(vals[0], ShouldResemble, foo2)
+                                        So(vals[1], ShouldResemble, data[2])
+
+                                        foo1 := &Foo{ID: 1, Parent: root, Value: []int64{2, 3}}
+                                        So(ds.Put(foo1), ShouldBeNil)
+
+                                        vals = []*Foo{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 3)
+
+                                        So(vals[0], ShouldResemble, foo1)
+                                        So(vals[1], ShouldResemble, foo2)
+                                        So(vals[2], ShouldResemble, data[2])
+
+                                        return nil
+                                }, nil), ShouldBeNil)
+                        })
+
+                        projectData := []*Foo{
+                                {ID: 2, Parent: root, Value: []int64{1, 2, 3, 4, 5, 6, 7}, Sort: []string{"x", "z"}},
+                                {ID: 3, Parent: root, Value: []int64{3, 4, 5, 6, 7, 8, 9}, Sort: []string{"b"}},
+                                {ID: 4, Parent: root, Value: []int64{3, 5, 7, 9, 11, 100, 1, 2}, Sort: []string{"aa", "a"}},
+                                {ID: 5, Parent: root, Value: []int64{1, 70, 101}, Sort: []string{"c"}},
+                        }
+
+                        Convey("project+extra orders", func() {
+
+                                _, _, ds := mkds(projectData)
+                                ds.Testable().AddIndexes(&datastore.IndexDefinition{
+                                        Kind:     "Foo",
+                                        Ancestor: true,
+                                        SortBy: []datastore.IndexColumn{
+                                                {Property: "Sort", Descending: true},
+                                                {Property: "Value", Descending: true},
+                                        },
+                                })
+
+                                q = q.Project("Value").Order("-Sort", "-Value").Distinct(true)
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds = datastore.Get(c)
+
+                                        So(ds.Put(&Foo{
+                                                ID: 1, Parent: root, Value: []int64{0, 1, 1000},
+                                                Sort: []string{"zz"}}), ShouldBeNil)
+
+                                        vals := []datastore.PropertyMap{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+
+                                        expect := []struct {
+                                                id  int64
+                                                val int64
+                                        }{
+                                                {1, 1000},
+                                                {1, 1},
+                                                {1, 0},
+                                                {2, 7},
+                                                {2, 6},
+                                                {2, 5},
+                                                {2, 4},
+                                                {2, 3},
+                                                {2, 2},
+                                                {5, 101},
+                                                {5, 70},
+                                                {3, 9},
+                                                {3, 8},
+                                                {4, 100},
+                                                {4, 11},
+                                        }
+
+                                        for i, pm := range vals {
+                                                So(pm["Value"][0].Value(), ShouldEqual, expect[i].val)
+                                                So(pm.GetMetaDefault("key", nil), ShouldResemble, ds.MakeKey("Parent", 1, "Foo", expect[i].id))
+                                        }
+
+                                        return nil
+                                }, nil), ShouldBeNil)
+                        })
+
+                        Convey("buffered entity sorts before ineq, but after first parent entity", func() {
+                                // If we got this wrong, we'd see Foo,3 come before Foo,2. This might
+                                // happen because we calculate the comparison string for each entity
+                                // based on the whole entity, but we forgot to limit the comparison
+                                // string generation by the inequality criteria.
+                                data := []*Foo{
+                                        {ID: 2, Parent: root, Value: []int64{2, 3, 5, 6}, Sort: []string{"z"}},
+                                }
+
+                                _, _, ds := mkds(data)
+                                ds.Testable().AddIndexes(&datastore.IndexDefinition{
+                                        Kind:     "Foo",
+                                        Ancestor: true,
+                                        SortBy: []datastore.IndexColumn{
+                                                {Property: "Value"},
+                                        },
+                                })
+
+                                q = q.Gt("Value", 2).Limit(2)
+
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds = datastore.Get(c)
+
+                                        foo1 := &Foo{ID: 3, Parent: root, Value: []int64{0, 2, 3, 4}}
+                                        So(ds.Put(foo1), ShouldBeNil)
+
+                                        vals := []*Foo{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 2)
+
+                                        So(vals[0], ShouldResemble, data[0])
+                                        So(vals[1], ShouldResemble, foo1)
+
+                                        return nil
+                                }, nil), ShouldBeNil)
+                        })
+
+                        Convey("keysOnly+extra orders", func() {
+                                _, _, ds := mkds(projectData)
+                                ds.Testable().AddIndexes(&datastore.IndexDefinition{
+                                        Kind:     "Foo",
+                                        Ancestor: true,
+                                        SortBy: []datastore.IndexColumn{
+                                                {Property: "Sort"},
+                                        },
+                                })
+
+                                q = q.Order("Sort").KeysOnly(true)
+
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds = datastore.Get(c)
+
+                                        So(ds.Put(&Foo{
+                                                ID: 1, Parent: root, Value: []int64{0, 1, 1000},
+                                                Sort: []string{"x", "zz"}}), ShouldBeNil)
+
+                                        So(ds.Put(&Foo{
+                                                ID: 2, Parent: root, Value: []int64{0, 1, 1000},
+                                                Sort: []string{"zz", "zzz", "zzzz"}}), ShouldBeNil)
+
+                                        vals := []*datastore.Key{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(len(vals), ShouldEqual, 5)
+
+                                        So(vals, ShouldResemble, []*datastore.Key{
+                                                ds.MakeKey("Parent", 1, "Foo", 4),
+                                                ds.MakeKey("Parent", 1, "Foo", 3),
+                                                ds.MakeKey("Parent", 1, "Foo", 5),
+                                                ds.MakeKey("Parent", 1, "Foo", 1),
+                                                ds.MakeKey("Parent", 1, "Foo", 2),
+                                        })
+
+                                        return nil
+                                }, nil), ShouldBeNil)
+                        })
+
+                        Convey("query accross nested transactions", func() {
+                                _, _, ds := mkds(projectData)
+                                q = q.Eq("Value", 2, 3)
+
+                                foo1 := &Foo{ID: 1, Parent: root, Value: []int64{2, 3}}
+                                foo7 := &Foo{ID: 7, Parent: root, Value: []int64{2, 3}}
+
+                                So(ds.RunInTransaction(func(c context.Context) error {
+                                        ds := datastore.Get(c)
+
+                                        So(ds.Put(foo1), ShouldBeNil)
+
+                                        vals := []*Foo{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(vals, ShouldResemble, []*Foo{foo1, projectData[0], projectData[2]})
+
+                                        So(ds.RunInTransaction(func(c context.Context) error {
+                                                ds := datastore.Get(c)
+
+                                                vals := []*Foo{}
+                                                So(ds.GetAll(q, &vals), ShouldBeNil)
+                                                So(vals, ShouldResemble, []*Foo{foo1, projectData[0], projectData[2]})
+
+                                                So(ds.Delete(ds.MakeKey("Parent", 1, "Foo", 4)), ShouldBeNil)
+                                                So(ds.Put(foo7), ShouldBeNil)
+
+                                                vals = []*Foo{}
+                                                So(ds.GetAll(q, &vals), ShouldBeNil)
+                                                So(vals, ShouldResemble, []*Foo{foo1, projectData[0], foo7})
+
+                                                return nil
+                                        }, nil), ShouldBeNil)
+
+                                        vals = []*Foo{}
+                                        So(ds.GetAll(q, &vals), ShouldBeNil)
+                                        So(vals, ShouldResemble, []*Foo{foo1, projectData[0], foo7})
+
+                                        return nil
+                                }, nil), ShouldBeNil)
+
+                                vals := []*Foo{}
+                                So(ds.GetAll(q, &vals), ShouldBeNil)
+                                So(vals, ShouldResemble, []*Foo{foo1, projectData[0], foo7})
+
+                        })
+
+                })
+
+        })
+
+}