LogDog: Enable keys-only BigTable queries.

server/logdog/storage/memory/memory.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 memory
 
 import (
         "errors"
         "sync"
         "time"
@@ skipping 103 matching lines @@
                 return nil
         })
         if err != nil {
                 return err
         }
 
         // Punt all of the records upstream. We copy the data to prevent the
         // callback from accidentally mutating it. We reuse the data buffer to try
         // and catch errors when the callback retains the data.
         for _, r := range recs {
-                dataCopy := make([]byte, len(r.data))
-                copy(dataCopy, r.data)
+                var dataCopy []byte
+                if !req.KeysOnly {
+                        dataCopy = make([]byte, len(r.data))
+                        copy(dataCopy, r.data)
+                }
                 if !cb(r.index, dataCopy) {
                         break
                 }
         }
 
         return nil
 }
 
 // Tail implements storage.Storage.
 func (s *Storage) Tail(p types.StreamPath) ([]byte, types.MessageIndex, error) {
@@ skipping 60 matching lines @@
                 }
 
                 if s.streams == nil {
                         s.streams = map[types.StreamPath]*logStream{}
                 }
                 s.streams[p] = ls
         }
 
         return ls
 }