Add __namespace__ metadata query support to impl/memory.

service/datastore/query.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 datastore
 
 import (
         "bytes"
         "fmt"
         "sort"
@@ skipping 551 matching lines @@
                 eqFilts: q.eqFilts,
 
                 ineqFiltProp:     q.ineqFiltProp,
                 ineqFiltLow:      q.ineqFiltLow,
                 ineqFiltLowIncl:  q.ineqFiltLowIncl,
                 ineqFiltLowSet:   q.ineqFiltLowSet,
                 ineqFiltHigh:     q.ineqFiltHigh,
                 ineqFiltHighIncl: q.ineqFiltHighIncl,
                 ineqFiltHighSet:  q.ineqFiltHighSet,
         }
+        // If a starting cursor is provided, ignore the offset, as it would have been
+        // accounted for in the query that produced the cursor.
+        if ret.start != nil {
+                ret.offset = nil
+        }

[iannucci, 2016/04/15 23:47:47]

This fixes a bug where doing:

  q = Query("Foo").Offset(1)
  Run(q, func(val, getCursor) error {
    assert val.Key.ID == 2 
    curs = getCursor()
    return Stop
  })
  q = q.Start(curs)
  Run(q, func(val) error {
    assert val.Key.ID == 3  // fails: ID == 4 because we applied 
                            // the offset on top of the cursor
    return Stop
  })

 
         if q.project != nil {
                 ret.project = q.project.ToSlice()
                 ret.distinct = q.distinct && q.project.Len() > 0
 
                 // If we're DISTINCT && have an inequality filter, we must project that
                 // inequality property as well.
                 if ret.distinct && ret.ineqFiltProp != "" && !q.project.Has(ret.ineqFiltProp) {
                         ret.project = append([]string{ret.ineqFiltProp}, ret.project...)
                 }
@@ skipping 151 matching lines @@
         if q.keysOnly {
                 p("KeysOnly")
         }
 
         if _, err := ret.WriteRune(')'); err != nil {
                 panic(err)
         }
 
         return ret.String()
 }