Remove dsQueryBatch in favor of ds.Batcher.

dm/appengine/deps/walk_graph.go

Index: dm/appengine/deps/walk_graph.go
diff --git a/dm/appengine/deps/walk_graph.go b/dm/appengine/deps/walk_graph.go
index 0c0ab4f04a901c081bf114937e84da9e7c38f43c..aa07f259ba3f63d19e81014114aa057341c2e4ed 100644
--- a/dm/appengine/deps/walk_graph.go
+++ b/dm/appengine/deps/walk_graph.go
@@ -14,8 +14,8 @@ import (
 	"golang.org/x/net/context"
 	"google.golang.org/grpc/codes"
 
-	"github.com/luci/gae/filter/dsQueryBatch"
 	ds "github.com/luci/gae/service/datastore"
+
 	"github.com/luci/luci-go/common/clock"
 	"github.com/luci/luci-go/common/logging"
 	"github.com/luci/luci-go/common/sync/parallel"
@@ -29,6 +29,12 @@ const numWorkers = 16
 
 const maxTimeout = 55 * time.Second // GAE limit is 60s
 
+// queryBatcher is a default datastore Batcher instance for queries.
+//
+// we end up doing a lot of long queries in here, so use a batcher to
+// prevent datastore timeouts.
+var queryBatcher ds.Batcher
+
 type node struct {
 	aid                 *dm.Attempt_ID
 	depth               int64
@@ -57,7 +63,7 @@ func (g *graphWalker) runAttemptListQuery(send func(*dm.Attempt_ID) error) func(
 				if !g.req.Include.Attempt.Expired {
 					qry = qry.Eq("IsExpired", false)
 				}
-				err := ds.Run(g, qry, func(k *ds.Key) error {
+				err := queryBatcher.Run(g, qry, func(k *ds.Key) error {
 					aid := &dm.Attempt_ID{}
 					if err := aid.SetDMEncoded(k.StringID()); err != nil {
 						logging.WithError(err).Errorf(g, "Attempt_ID.SetDMEncoded returned an error with input: %q", k.StringID())
@@ -113,7 +119,7 @@ func (g *graphWalker) questDataLoader(qid string, dst *dm.Quest) func() error {
 }
 
 func (g *graphWalker) loadEdges(send func(*dm.Attempt_ID) error, typ string, base *ds.Key, fan *dm.AttemptList, doSend bool) error {
-	return ds.Run(g, ds.NewQuery(typ).Ancestor(base), func(k *ds.Key) error {
+	return queryBatcher.Run(g, ds.NewQuery(typ).Ancestor(base), func(k *ds.Key) error {
 		if g.Err() != nil {
 			return ds.Stop
 		}
@@ -154,7 +160,7 @@ func (g *graphWalker) loadExecutions(includeResult bool, atmpt *model.Attempt, a
 		q = q.Eq("IsExpired", false)
 	}
 
-	return ds.Run(g, q, func(e *model.Execution) error {
+	return queryBatcher.Run(g, q, func(e *model.Execution) error {
 		if g.Err() != nil {
 			return ds.Stop
 		}
@@ -420,9 +426,6 @@ func doGraphWalk(c context.Context, req *dm.WalkGraphReq) (rsp *dm.GraphData, er
 	if timeoutProto == nil || timeout > maxTimeout {
 		timeout = maxTimeout
 	}
-	// we end up doing a lot of long queries in here, so install a batcher to
-	// prevent datastore timeouts.
-	c = dsQueryBatch.BatchQueries(c, 100)
 	c, cncl = clock.WithTimeout(c, timeout)
 	defer cncl()