impl/memory: Implement Queries

impl/memory/taskqueue_data.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"
         "fmt"
         "net/http"
@@ skipping 178 matching lines @@
         closed int32
         anony  tq.AnonymousQueueData
         parent *taskQueueData
 }
 
 var _ interface {
         memContextObj
         tq.Testable
 } = (*txnTaskQueueData)(nil)
 
-func (t *txnTaskQueueData) canApplyTxn(obj memContextObj) bool         { return false }
-func (t *txnTaskQueueData) applyTxn(context.Context, memContextObj)    { panic("impossible") }
-func (t *txnTaskQueueData) mkTxn(*ds.TransactionOptions) memContextObj { panic("impossible") }
+func (t *txnTaskQueueData) canApplyTxn(obj memContextObj) bool { return false }
+func (t *txnTaskQueueData) applyTxn(context.Context, memContextObj) {
+        impossible(fmt.Errorf("cannot apply nested transaction"))
+}
+func (t *txnTaskQueueData) mkTxn(*ds.TransactionOptions) memContextObj {
+        impossible(fmt.Errorf("cannot start nested transaction"))
+        return nil
+}
 
 func (t *txnTaskQueueData) endTxn() {
         if atomic.LoadInt32(&t.closed) == 1 {
                 panic("cannot end transaction twice")
         }
         atomic.StoreInt32(&t.closed, 1)
 }
 
 func (t *txnTaskQueueData) ResetTasks() {
         t.Lock()
@@ skipping 35 matching lines @@
         return t.parent.GetTombstonedTasks()
 }
 
 func (t *txnTaskQueueData) GetScheduledTasks() tq.QueueData {
         return t.parent.GetScheduledTasks()
 }
 
 func (t *txnTaskQueueData) CreateQueue(queueName string) {
         t.parent.CreateQueue(queueName)
 }