Use the sort.Search api correctly.

service/datastore/query_test.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 (
         "math"
         "testing"
 
@@ skipping 235 matching lines @@
                 nq().Order("a", "b", "c").Eq("b", 2, 2),
                 "SELECT * FROM `Foo` WHERE `b` = 2 ORDER BY `a`, `c`, `__key__`",
                 nil, nq().Order("a", "c").Eq("b", 2)},
 
         {"sort orders used for equality are ignored (reversed)",
                 nq().Eq("b", 2).Order("a", "b", "c"),
                 "SELECT * FROM `Foo` WHERE `b` = 2 ORDER BY `a`, `c`, `__key__`",
                 nil,
                 nq().Order("a", "c").Eq("b", 2)},
 
+        {"duplicate equality filters are ignored",
+                nq().Eq("b", 10, -1, 2, 2, 7, 1, 2, 10, -1, 7, 1, 2),
+                "SELECT * FROM `Foo` WHERE `b` = -1 AND `b` = 1 AND `b` = 2 AND `b` = 7 AND `b` = 10 ORDER BY `__key__`",
+                nil,
+                nq().Eq("b", -1, 1, 2, 7, 10)},
+
         {"duplicate orders are ignored",
                 nq().Order("a").Order("a").Order("a"),
                 "SELECT * FROM `Foo` ORDER BY `a`, `__key__`",
                 nil,
                 nq().Order("a")},
 
         {"Filtering on a reserved property is forbidden",
                 nq().Gte("__special__", 10),
                 "",
                 "cannot filter/project on reserved property: \"__special__\"",
@@ skipping 56 matching lines @@
                                         So(err, ShouldBeNil)
 
                                         fq.original = nil
                                         fq2.original = nil
                                         So(fq, ShouldResemble, fq2)
                                 }
                         })
                 }
         })
 }