Add __namespace__ metadata query support to impl/memory.

service/datastore/query.go

Index: service/datastore/query.go
diff --git a/service/datastore/query.go b/service/datastore/query.go
index 2e60b90cda8e90ce8fe0b95f88a21635cd6d3dcd..8c15f9b5a57a64d08275a448f91a09fed281ec1d 100644
--- a/service/datastore/query.go
+++ b/service/datastore/query.go
@@ -569,6 +569,11 @@ func (q *Query) Finalize() (*FinalizedQuery, error) {
 		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()