Add initial Query generation, correctness checking and index generation.

go/src/infra/gae/libs/wrapper/memory/datastore_query.go

Index: go/src/infra/gae/libs/wrapper/memory/datastore_query.go
diff --git a/go/src/infra/gae/libs/wrapper/memory/datastore_query.go b/go/src/infra/gae/libs/wrapper/memory/datastore_query.go
new file mode 100644
index 0000000000000000000000000000000000000000..8e807be42e1aa219b2f5898bb2194821a0350083
--- /dev/null
+++ b/go/src/infra/gae/libs/wrapper/memory/datastore_query.go
@@ -0,0 +1,567 @@
+// 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 memory
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"math"
+	"strings"
+
+	"appengine/datastore"
+	pb "appengine_internal/datastore"
+
+	"github.com/luci/gkvlite"
+	"github.com/luci/luci-go/common/funnybase"
+
+	"infra/gae/libs/wrapper"
+)
+
+type qDirection bool
+
+const (
+	qASC qDirection = true
+	qDEC            = false
+)
+
+var builtinQueryPrefix = []byte{0}
+var complexQueryPrefix = []byte{1}
+
+type qSortBy struct {
+	prop string
+	dir  qDirection
+}
+
+func (q qSortBy) WriteBinary(buf *bytes.Buffer) {
+	if q.dir == qASC {
+		buf.WriteByte(0)
+	} else {
+		buf.WriteByte(1)
+	}
+	writeString(buf, q.prop)
+}
+
+func (q *qSortBy) ReadBinary(buf *bytes.Buffer) error {
+	dir, err := buf.ReadByte()
+	if err != nil {
+		return err
+	}
+	q.dir = dir == 0
+	q.prop, err = readString(buf)
+	return err
+}
+
+type qIndex struct {
+	kind     string
+	ancestor bool
+	sortby   []qSortBy
+}
+
+func (i *qIndex) Builtin() bool {
+	return !i.ancestor && len(i.sortby) <= 1
+}
+
+// Valid verifies that this qIndex doesn't have duplicate sortBy fields.
+func (i *qIndex) Valid() bool {
+	names := map[string]bool{}
+	for _, sb := range i.sortby {
+		if names[sb.prop] {
+			return false
+		}
+		names[sb.prop] = true
+	}
+	return true
+}
+
+func (i *qIndex) WriteBinary(buf *bytes.Buffer) {
+	// TODO(riannucci): do a Grow call here?
+	if i.Builtin() {
+		buf.Write(builtinQueryPrefix)
+	} else {
+		buf.Write(complexQueryPrefix)
+	}
+	writeString(buf, i.kind)
+	if i.ancestor {
+		buf.WriteByte(0)
+	} else {
+		buf.WriteByte(1)
+	}
+	funnybase.WriteUint(buf, uint64(len(i.sortby)))
+	for _, sb := range i.sortby {
+		sb.WriteBinary(buf)
+	}
+}
+
+func (i *qIndex) String() string {
+	ret := &bytes.Buffer{}
+	if i.Builtin() {
+		ret.WriteRune('B')
+	} else {
+		ret.WriteRune('C')
+	}
+	ret.WriteRune(':')
+	ret.WriteString(i.kind)
+	if i.ancestor {
+		ret.WriteString("|A")
+	}
+	for _, sb := range i.sortby {
+		ret.WriteRune('/')
+		if sb.dir == qDEC {
+			ret.WriteRune('-')
+		}
+		ret.WriteString(sb.prop)
+	}
+	return ret.String()
+}
+
+func (i *qIndex) ReadBinary(buf *bytes.Buffer) error {
+	// discard builtin/complex byte
+	_, err := buf.ReadByte()
+	if err != nil {
+		return err
+	}
+
+	i.kind, err = readString(buf)
+	if err != nil {
+		return err
+	}
+	anc, err := buf.ReadByte()
+	if err != nil {
+		return err
+	}
+	i.ancestor = anc == 1
+
+	numSorts, err := funnybase.ReadUint(buf)
+	if err != nil {
+		return err
+	}
+	if numSorts > 64 {
+		return fmt.Errorf("qIndex.ReadBinary: Got over 64 sort orders: %d", numSorts)
+	}
+	i.sortby = make([]qSortBy, numSorts)
+	for idx := range i.sortby {
+		err = (&i.sortby[idx]).ReadBinary(buf)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+type queryOp int
+
+const (
+	qInvalid queryOp = iota
+	qEqual
+	qLessThan
+	qLessEq
+	qGreaterEq
+	qGreaterThan
+)
+
+func (o queryOp) isEQOp() bool {
+	return o == qEqual
+}
+
+func (o queryOp) isINEQOp() bool {
+	return o >= qLessThan && o <= qGreaterThan
+}
+
+var queryOpMap = map[string]queryOp{
+	"=":  qEqual,
+	"<":  qLessThan,
+	"<=": qLessEq,
+	">=": qGreaterEq,
+	">":  qGreaterThan,
+}
+
+type queryFilter struct {
+	field string
+	op    queryOp
+	value interface{}
+}
+
+func parseFilter(f string, v interface{}) (ret queryFilter, err error) {
+	toks := strings.SplitN(strings.TrimSpace(f), " ", 2)
+	if len(toks) != 2 {
+		err = errors.New("datastore: invalid filter: " + f)
+	} else {
+		op := queryOpMap[toks[1]]
+		if op == qInvalid {
+			err = fmt.Errorf("datastore: invalid operator %q in filter %q", toks[1], f)
+		} else {
+			ret.field = toks[0]
+			ret.op = op
+			ret.value = v
+		}
+	}
+	return
+}
+
+type queryOrder struct {
+	field     string
+	direction qDirection
+}
+
+type queryCursor string
+
+func (q queryCursor) String() string { return string(q) }
+func (q queryCursor) Valid() bool    { return q != "" }
+
+type queryImpl struct {
+	wrapper.DSQuery
+
+	ns string
+
+	kind     string
+	ancestor *datastore.Key
+	filter   []queryFilter
+	order    []queryOrder
+
+	keysOnly bool
+	limit    int32
+	offset   int32
+
+	start queryCursor
+	end   queryCursor
+
+	err error
+}
+
+type queryIterImpl struct {
+	idx *queryImpl
+}
+
+func (q *queryIterImpl) Cursor() (wrapper.DSCursor, error) {
+	if q.idx.err != nil {
+		return nil, q.idx.err
+	}
+	return nil, nil
+}
+
+func (q *queryIterImpl) Next(dst interface{}) (*datastore.Key, error) {
+	if q.idx.err != nil {
+		return nil, q.idx.err
+	}
+	return nil, nil
+}
+
+func (q *queryImpl) normalize() (ret *queryImpl) {
+	// ported from GAE SDK datastore_index.py;Normalize()
+	ret = q.clone()
+
+	bs := newMemStore()
+
+	eqProperties := bs.MakePrivateCollection(nil)
+
+	ineqProperties := bs.MakePrivateCollection(nil)
+
+	for _, f := range ret.filter {
+		// if we supported the IN operator, we would check to see if there were
+		// multiple value operands here, but the go SDK doesn't support this.
+		if f.op.isEQOp() {
+			eqProperties.Set([]byte(f.field), []byte{})
+		} else if f.op.isINEQOp() {
+			ineqProperties.Set([]byte(f.field), []byte{})
+		}
+	}
+
+	ineqProperties.VisitItemsAscend(nil, false, func(i *gkvlite.Item) bool {
+		eqProperties.Delete(i.Key)
+		return true
+	})
+
+	removeSet := bs.MakePrivateCollection(nil)
+	eqProperties.VisitItemsAscend(nil, false, func(i *gkvlite.Item) bool {
+		removeSet.Set(i.Key, []byte{})
+		return true
+	})
+
+	newOrders := []queryOrder{}
+	for _, o := range ret.order {
+		if removeSet.Get([]byte(o.field)) == nil {
+			removeSet.Set([]byte(o.field), []byte{})
+			newOrders = append(newOrders, o)
+		}
+	}
+	ret.order = newOrders
+
+	// need to fix ret.filters if we ever support the EXISTS operator and/or
+	// projections.
+	//
+	//   newFilters = []
+	//   for f in ret.filters:
+	//     if f.op != qExists:
+	//       newFilters = append(newFilters, f)
+	//     if !removeSet.Has(f.field):
+	//       removeSet.InsertNoReplace(f.field)
+	//       newFilters = append(newFilters, f)
+	//
+	// so ret.filters == newFilters becuase none of ret.filters has op == qExists
+	//
+	// then:
+	//
+	//   for prop in ret.project:
+	//     if !removeSet.Has(prop):
+	//       removeSet.InsertNoReplace(prop)
+	//      ... make new EXISTS filters, add them to newFilters ...
+	//   ret.filters = newFilters
+	//
+	// However, since we don't support projection queries, this is moot.
+
+	if eqProperties.Get([]byte("__key__")) != nil {
+		ret.order = []queryOrder{}
+	}
+
+	newOrders = []queryOrder{}
+	for _, o := range ret.order {
+		if o.field == "__key__" {
+			newOrders = append(newOrders, o)
+			break
+		}
+		newOrders = append(newOrders, o)
+	}
+	ret.order = newOrders
+
+	return
+}
+
+func (q *queryImpl) checkCorrectness(ns string, isTxn bool) (ret *queryImpl) {
+	// ported from GAE SDK datastore_stub_util.py;CheckQuery()
+	ret = q.clone()
+
+	if ns != ret.ns {
+		ret.err = newDSError(pb.Error_BAD_REQUEST,
+			"MADE UP ERROR: Namespace mismatched. Query and Datastore don't agree "+
+				"on the current namespace")
+		return
+	}
+
+	if ret.err != nil {
+		return
+	}
+
+	// if projection && keys_only:
+	//   "projection and keys_only cannot both be set"
+
+	// if projection props match /^__.*__$/:
+	//   "projections are not supported for the property: %(prop)s"
+
+	if isTxn && ret.ancestor == nil {
+		ret.err = newDSError(pb.Error_BAD_REQUEST,
+			"Only ancestor queries are allowed inside transactions")
+		return
+	}
+
+	numComponents := len(ret.filter) + len(ret.order)
+	if ret.ancestor != nil {
+		numComponents++
+	}
+	if numComponents > 100 {
+		ret.err = newDSError(pb.Error_BAD_REQUEST,
+			"query is too large. may not have more than "+
+				"100 filters + sort orders ancestor total")
+	}
+
+	// if ret.ancestor.appid() != current appid
+	//   "query app is x but ancestor app is x"
+	// if ret.ancestor.namespace() != current namespace
+	//   "query namespace is x but ancestor namespace is x"
+
+	// if not all(g in orders for g in group_by)
+	//  "items in the group by clause must be specified first in the ordering"
+
+	ineqPropName := ""
+	for _, f := range ret.filter {
+		if f.field == "__key__" {
+			k, ok := f.value.(*datastore.Key)
+			if !ok {
+				ret.err = newDSError(pb.Error_BAD_REQUEST,
+					"__key__ filter value must be a Key")
+				return
+			}
+			if !keyValid(ret.ns, k, userKeyOnly) {
+				// See the comment in queryImpl.Ancestor; basically this check
+				// never happens in the real env because the SDK silently swallows
+				// this condition :/
+				ret.err = datastore.ErrInvalidKey
+				return
+			}
+			// __key__ filter app is X but query app is X
+			// __key__ filter namespace is X but query namespace is X
+		}
+		// if f.op == qEqual and f.field in ret.project_fields
+		//   "cannot use projection on a proprety with an equality filter"
+
+		if f.op.isINEQOp() {
+			if ineqPropName == "" {
+				ineqPropName = f.field
+			} else if f.field != ineqPropName {
+				ret.err = newDSError(pb.Error_BAD_REQUEST,
+					fmt.Sprintf(
+						"Only one inequality filter per query is supported. "+
+							"Encountered both %s and %s", ineqPropName, f.field))
+				return
+			}
+		}
+	}
+
+	// if ineqPropName != "" && len(group_by) > 0 && len(orders) ==0
+	//   "Inequality filter on X must also be a group by property "+
+	//   "when group by properties are set."
+
+	if ineqPropName != "" && len(ret.order) != 0 {
+		if ret.order[0].field != ineqPropName {
+			ret.err = newDSError(pb.Error_BAD_REQUEST,
+				fmt.Sprintf(
+					"The first sort property must be the same as the property "+
+						"to which the inequality filter is applied.  In your query "+
+						"the first sort property is %s but the inequality filter "+
+						"is on %s", ret.order[0].field, ineqPropName))
+			return
+		}
+	}
+
+	if ret.kind == "" {
+		for _, f := range ret.filter {
+			if f.field != "__key__" {
+				ret.err = newDSError(pb.Error_BAD_REQUEST,
+					"kind is required for non-__key__ filters")
+				return
+			}
+		}
+		for _, o := range ret.order {
+			if o.field != "__key__" || o.direction != qASC {
+				ret.err = newDSError(pb.Error_BAD_REQUEST,
+					"kind is required for all orders except __key__ ascending")
+				return
+			}
+		}
+	}
+	return
+}
+
+func (q *queryImpl) calculateIndex() *qIndex {
+	// as a nod to simplicity in this code, we'll require that a single index
+	// is able to service the entire query. E.g. no zigzag merge joins or
+	// multiqueries. This will mean that the user will need to rely on
+	// dev_appserver to tell them what indicies they need for real, and for thier
+	// tests they'll need to specify the missing composite indices manually.
+	//
+	// This COULD lead to an exploding indicies problem, but we can fix that when
+	// we get to it.
+
+	//sortOrders := []qSortBy{}
+
+	return nil
+}
+
+func (q *queryImpl) clone() *queryImpl {
+	ret := *q
+	ret.filter = append([]queryFilter(nil), q.filter...)
+	ret.order = append([]queryOrder(nil), q.order...)
+	return &ret
+}
+
+func (q *queryImpl) Ancestor(k *datastore.Key) wrapper.DSQuery {
+	q = q.clone()
+	q.ancestor = k
+	if k == nil {
+		// SDK has an explicit nil-check
+		q.err = errors.New("datastore: nil query ancestor")
+	} else if !keyValid(q.ns, k, userKeyOnly) {
+		// technically the SDK implementation does a Weird Thing (tm) if both the
+		// stringID and intID are set on a key; it only serializes the stringID in
+		// the proto. This means that if you set the Ancestor to an invalid key,
+		// you'll never actually hear about it. Instead of doing that insanity, we
+		// just swap to an error here.
+		q.err = datastore.ErrInvalidKey
+	}
+	return q
+}
+
+func (q *queryImpl) Filter(fStr string, val interface{}) wrapper.DSQuery {
+	q = q.clone()
+	f, err := parseFilter(fStr, val)
+	if err != nil {
+		q.err = err
+		return q
+	}
+	q.filter = append(q.filter, f)
+	return q
+}
+
+func (q *queryImpl) Order(field string) wrapper.DSQuery {
+	q = q.clone()
+	field = strings.TrimSpace(field)
+	o := queryOrder{field, qASC}
+	if strings.HasPrefix(field, "-") {
+		o.direction = qDEC
+		o.field = strings.TrimSpace(field[1:])
+	} else if strings.HasPrefix(field, "+") {
+		q.err = fmt.Errorf("datastore: invalid order: %q", field)
+		return q
+	}
+	if len(o.field) == 0 {
+		q.err = errors.New("datastore: empty order")
+		return q
+	}
+	q.order = append(q.order, o)
+	return q
+}
+
+func (q *queryImpl) KeysOnly() wrapper.DSQuery {
+	q = q.clone()
+	q.keysOnly = true
+	return q
+}
+
+func (q *queryImpl) Limit(limit int) wrapper.DSQuery {
+	q = q.clone()
+	if limit < math.MinInt32 || limit > math.MaxInt32 {
+		q.err = errors.New("datastore: query limit overflow")
+		return q
+	}
+	q.limit = int32(limit)
+	return q
+}
+
+func (q *queryImpl) Offset(offset int) wrapper.DSQuery {
+	q = q.clone()
+	if offset < 0 {
+		q.err = errors.New("datastore: negative query offset")
+		return q
+	}
+	if offset > math.MaxInt32 {
+		q.err = errors.New("datastore: query offset overflow")
+		return q
+	}
+	q.offset = int32(offset)
+	return q
+}
+
+func (q *queryImpl) Start(c wrapper.DSCursor) wrapper.DSQuery {
+	q = q.clone()
+	curs := c.(queryCursor)
+	if !curs.Valid() {
+		q.err = errors.New("datastore: invalid cursor")
+		return q
+	}
+	q.start = curs
+	return q
+}
+
+func (q *queryImpl) End(c wrapper.DSCursor) wrapper.DSQuery {
+	q = q.clone()
+	curs := c.(queryCursor)
+	if !curs.Valid() {
+		q.err = errors.New("datastore: invalid cursor")
+		return q
+	}
+	q.end = curs
+	return q
+}