[SPARK-6463][SQL] AttributeSet.equal should compare size

Previously this could result in sets compare equals when in fact the right was a subset of the left.

Based on #5133 by sisihj

Author: sisihj <jun.hejun@huawei.com>
Author: Michael Armbrust <michael@databricks.com>

Closes #5194 from marmbrus/pr/5133 and squashes the following commits:

5ed4615 [Michael Armbrust] fix imports
d4cbbc0 [Michael Armbrust] Add test cases
0a0834f [sisihj]  AttributeSet.equal should compare size

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/AttributeSet.scala

@@ -58,7 +58,8 @@ class AttributeSet private (val baseSet: Set[AttributeEquals])
 
   /** Returns true if the members of this AttributeSet and other are the same. */
   override def equals(other: Any): Boolean = other match {
-    case otherSet: AttributeSet => baseSet.map(_.a).forall(otherSet.contains)
+    case otherSet: AttributeSet =>
+      otherSet.size == baseSet.size && baseSet.map(_.a).forall(otherSet.contains)
     case _ => false
   }
 

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/AttributeSetSuite.scala

@@ -0,0 +1,82 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.catalyst.expressions
+
+import org.scalatest.FunSuite
+
+import org.apache.spark.sql.types.IntegerType
+
+class AttributeSetSuite extends FunSuite {
+
+  val aUpper = AttributeReference("A", IntegerType)(exprId = ExprId(1))
+  val aLower = AttributeReference("a", IntegerType)(exprId = ExprId(1))
+  val fakeA = AttributeReference("a", IntegerType)(exprId = ExprId(3))
+  val aSet = AttributeSet(aLower :: Nil)
+
+  val bUpper = AttributeReference("B", IntegerType)(exprId = ExprId(2))
+  val bLower = AttributeReference("b", IntegerType)(exprId = ExprId(2))
+  val bSet = AttributeSet(bUpper :: Nil)
+
+  val aAndBSet = AttributeSet(aUpper :: bUpper :: Nil)
+
+  test("sanity check") {
+    assert(aUpper != aLower)
+    assert(bUpper != bLower)
+  }
+
+  test("checks by id not name") {
+    assert(aSet.contains(aUpper) === true)
+    assert(aSet.contains(aLower) === true)
+    assert(aSet.contains(fakeA) === false)
+
+    assert(aSet.contains(bUpper) === false)
+    assert(aSet.contains(bLower) === false)
+  }
+
+  test("++ preserves AttributeSet")  {
+    assert((aSet ++ bSet).contains(aUpper) === true)
+    assert((aSet ++ bSet).contains(aLower) === true)
+  }
+
+  test("extracts all references references") {
+    val addSet = AttributeSet(Add(aUpper, Alias(bUpper, "test")()):: Nil)
+    assert(addSet.contains(aUpper))
+    assert(addSet.contains(aLower))
+    assert(addSet.contains(bUpper))
+    assert(addSet.contains(bLower))
+  }
+
+  test("dedups attributes") {
+    assert(AttributeSet(aUpper :: aLower :: Nil).size === 1)
+  }
+
+  test("subset") {
+    assert(aSet.subsetOf(aAndBSet) === true)
+    assert(aAndBSet.subsetOf(aSet) === false)
+  }
+
+  test("equality") {
+    assert(aSet != aAndBSet)
+    assert(aAndBSet != aSet)
+    assert(aSet != bSet)
+    assert(bSet != aSet)
+
+    assert(aSet == aSet)
+    assert(aSet == AttributeSet(aUpper :: Nil))
+  }
+}