[SPARK-2218] rename Equals to EqualTo in Spark SQL expressions.

Due to the existence of scala.Equals, it is very error prone to name the expression Equals, especially because we use a lot of partial functions and pattern matching in the optimizer.

Note that this sits on top of #1144.

Author: Reynold Xin <rxin@apache.org>

Closes #1146 from rxin/equals and squashes the following commits:

f8583fd [Reynold Xin] Merge branch 'master' of github.com:apache/spark into equals
326b388 [Reynold Xin] Merge branch 'master' of github.com:apache/spark into equals
bd19807 [Reynold Xin] Rename EqualsTo to EqualTo.
81148d1 [Reynold Xin] [SPARK-2218] rename Equals to EqualsTo in Spark SQL expressions.
c4e543d [Reynold Xin] [SPARK-2210] boolean cast on boolean value should be removed.

11 files changed, 38 insertions, 40 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala
index 2ad2d04af5..0cc4592047 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala
@@ -258,13 +258,13 @@ class SqlParser extends StandardTokenParsers with PackratParsers {
     comparisonExpression * (AND ^^^ { (e1: Expression, e2: Expression) => And(e1,e2) })
 
   protected lazy val comparisonExpression: Parser[Expression] =
-    termExpression ~ "=" ~ termExpression ^^ { case e1 ~ _ ~ e2 => Equals(e1, e2) } |
+    termExpression ~ "=" ~ termExpression ^^ { case e1 ~ _ ~ e2 => EqualTo(e1, e2) } |
     termExpression ~ "<" ~ termExpression ^^ { case e1 ~ _ ~ e2 => LessThan(e1, e2) } |
     termExpression ~ "<=" ~ termExpression ^^ { case e1 ~ _ ~ e2 => LessThanOrEqual(e1, e2) } |
     termExpression ~ ">" ~ termExpression ^^ { case e1 ~ _ ~ e2 => GreaterThan(e1, e2) } |
     termExpression ~ ">=" ~ termExpression ^^ { case e1 ~ _ ~ e2 => GreaterThanOrEqual(e1, e2) } |
-    termExpression ~ "!=" ~ termExpression ^^ { case e1 ~ _ ~ e2 => Not(Equals(e1, e2)) } |
-    termExpression ~ "<>" ~ termExpression ^^ { case e1 ~ _ ~ e2 => Not(Equals(e1, e2)) } |
+    termExpression ~ "!=" ~ termExpression ^^ { case e1 ~ _ ~ e2 => Not(EqualTo(e1, e2)) } |
+    termExpression ~ "<>" ~ termExpression ^^ { case e1 ~ _ ~ e2 => Not(EqualTo(e1, e2)) } |
     termExpression ~ RLIKE ~ termExpression ^^ { case e1 ~ _ ~ e2 => RLike(e1, e2) } |
     termExpression ~ REGEXP ~ termExpression ^^ { case e1 ~ _ ~ e2 => RLike(e1, e2) } |
     termExpression ~ LIKE ~ termExpression ^^ { case e1 ~ _ ~ e2 => Like(e1, e2) } |
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala
index c0714bcdd0..76ddeba9cb 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala
@@ -234,8 +234,8 @@ trait HiveTypeCoercion {
     def apply(plan: LogicalPlan): LogicalPlan = plan transformAllExpressions {
       // Skip nodes who's children have not been resolved yet.
       case e if !e.childrenResolved => e
-      // No need to change Equals operators as that actually makes sense for boolean types.
-      case e: Equals => e
+      // No need to change EqualTo operators as that actually makes sense for boolean types.
+      case e: EqualTo => e
       // Otherwise turn them to Byte types so that there exists and ordering.
       case p: BinaryComparison
           if p.left.dataType == BooleanType && p.right.dataType == BooleanType =>
@@ -254,7 +254,10 @@ trait HiveTypeCoercion {
       // Skip if the type is boolean type already. Note that this extra cast should be removed
       // by optimizer.SimplifyCasts.
       case Cast(e, BooleanType) if e.dataType == BooleanType => e
-      case Cast(e, BooleanType) => Not(Equals(e, Literal(0)))
+      // If the data type is not boolean and is being cast boolean, turn it into a comparison
+      // with the numeric value, i.e. x != 0. This will coerce the type into numeric type.
+      case Cast(e, BooleanType) if e.dataType != BooleanType => Not(EqualTo(e, Literal(0)))
+      // Turn true into 1, and false into 0 if casting boolean into other types.
       case Cast(e, dataType) if e.dataType == BooleanType =>
         Cast(If(e, Literal(1), Literal(0)), dataType)
     }
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/dsl/package.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/dsl/package.scala
index d177339d40..26ad4837b0 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/dsl/package.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/dsl/package.scala
@@ -44,7 +44,7 @@ import org.apache.spark.sql.catalyst.types._
  *
  *  // These unresolved attributes can be used to create more complicated expressions.
  *  scala> 'a === 'b
- *  res2: org.apache.spark.sql.catalyst.expressions.Equals = ('a = 'b)
+ *  res2: org.apache.spark.sql.catalyst.expressions.EqualTo = ('a = 'b)
  *
  *  // SQL verbs can be used to construct logical query plans.
  *  scala> import org.apache.spark.sql.catalyst.plans.logical._
@@ -76,8 +76,8 @@ package object dsl {
     def <= (other: Expression) = LessThanOrEqual(expr, other)
     def > (other: Expression) = GreaterThan(expr, other)
     def >= (other: Expression) = GreaterThanOrEqual(expr, other)
-    def === (other: Expression) = Equals(expr, other)
-    def !== (other: Expression) = Not(Equals(expr, other))
+    def === (other: Expression) = EqualTo(expr, other)
+    def !== (other: Expression) = Not(EqualTo(expr, other))
 
     def like(other: Expression) = Like(expr, other)
     def rlike(other: Expression) = RLike(expr, other)
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/package.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/package.scala
index 573ec052f4..b6f2451b52 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/package.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/package.scala
@@ -24,7 +24,7 @@ package org.apache.spark.sql.catalyst
  * expression, a [[NamedExpression]] in addition to the standard collection of expressions.
  *
  * ==Standard Expressions==
- * A library of standard expressions (e.g., [[Add]], [[Equals]]), aggregates (e.g., SUM, COUNT),
+ * A library of standard expressions (e.g., [[Add]], [[EqualTo]]), aggregates (e.g., SUM, COUNT),
  * and other computations (e.g. UDFs). Each expression type is capable of determining its output
  * schema as a function of its children's output schema.
  *
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
index 2718d43646..b63406b94a 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
@@ -52,7 +52,7 @@ trait PredicateHelper {
    *
    * For example consider a join between two relations R(a, b) and S(c, d).
    *
-   * `canEvaluate(Equals(a,b), R)` returns `true` where as `canEvaluate(Equals(a,c), R)` returns
+   * `canEvaluate(EqualTo(a,b), R)` returns `true` where as `canEvaluate(EqualTo(a,c), R)` returns
    * `false`.
    */
   protected def canEvaluate(expr: Expression, plan: LogicalPlan): Boolean =
@@ -140,7 +140,7 @@ abstract class BinaryComparison extends BinaryPredicate {
   self: Product =>
 }
 
-case class Equals(left: Expression, right: Expression) extends BinaryComparison {
+case class EqualTo(left: Expression, right: Expression) extends BinaryComparison {
   def symbol = "="
   override def eval(input: Row): Any = {
     val l = left.eval(input)
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/patterns.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/patterns.scala
index 820ecfb78b..a43bef389c 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/patterns.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/patterns.scala
@@ -136,14 +136,14 @@ object HashFilteredJoin extends Logging with PredicateHelper {
     val Join(left, right, joinType, _) = join
     val (joinPredicates, otherPredicates) =
       allPredicates.flatMap(splitConjunctivePredicates).partition {
-        case Equals(l, r) if (canEvaluate(l, left) && canEvaluate(r, right)) ||
+        case EqualTo(l, r) if (canEvaluate(l, left) && canEvaluate(r, right)) ||
           (canEvaluate(l, right) && canEvaluate(r, left)) => true
         case _ => false
       }
 
     val joinKeys = joinPredicates.map {
-      case Equals(l, r) if canEvaluate(l, left) && canEvaluate(r, right) => (l, r)
-      case Equals(l, r) if canEvaluate(l, right) && canEvaluate(r, left) => (r, l)
+      case EqualTo(l, r) if canEvaluate(l, left) && canEvaluate(r, right) => (l, r)
+      case EqualTo(l, r) if canEvaluate(l, right) && canEvaluate(r, left) => (r, l)
     }
 
     // Do not consider this strategy if there are no join keys.
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ConstantFoldingSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ConstantFoldingSuite.scala
index cea97c584f..0ff8206401 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ConstantFoldingSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ConstantFoldingSuite.scala
@@ -195,8 +195,8 @@ class ConstantFoldingSuite extends PlanTest {
           Add(Literal(null, IntegerType), 1) as 'c9,
           Add(1, Literal(null, IntegerType)) as 'c10,
 
-          Equals(Literal(null, IntegerType), 1) as 'c11,
-          Equals(1, Literal(null, IntegerType)) as 'c12,
+          EqualTo(Literal(null, IntegerType), 1) as 'c11,
+          EqualTo(1, Literal(null, IntegerType)) as 'c12,
 
           Like(Literal(null, StringType), "abc") as 'c13,
           Like("abc", Literal(null, StringType)) as 'c14,
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/parquet/ParquetFilters.scala b/sql/core/src/main/scala/org/apache/spark/sql/parquet/ParquetFilters.scala
index 052b0a9196..cc575bedd8 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/parquet/ParquetFilters.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/parquet/ParquetFilters.scala
@@ -205,9 +205,9 @@ object ParquetFilters {
             Some(new AndFilter(leftFilter.get, rightFilter.get))
         }
       }
-      case p @ Equals(left: Literal, right: NamedExpression) if !right.nullable =>
+      case p @ EqualTo(left: Literal, right: NamedExpression) if !right.nullable =>
         Some(createEqualityFilter(right.name, left, p))
-      case p @ Equals(left: NamedExpression, right: Literal) if !left.nullable =>
+      case p @ EqualTo(left: NamedExpression, right: Literal) if !left.nullable =>
         Some(createEqualityFilter(left.name, right, p))
       case p @ LessThan(left: Literal, right: NamedExpression) if !right.nullable =>
         Some(createLessThanFilter(right.name, left, p))
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/parquet/ParquetQuerySuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/parquet/ParquetQuerySuite.scala
index 0c239d00b1..7714eb1b56 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/parquet/ParquetQuerySuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/parquet/ParquetQuerySuite.scala
@@ -19,27 +19,23 @@ package org.apache.spark.sql.parquet
 
 import org.scalatest.{BeforeAndAfterAll, FunSuiteLike}
 
-import org.apache.hadoop.fs.{Path, FileSystem}
-import org.apache.hadoop.mapreduce.Job
-
 import parquet.hadoop.ParquetFileWriter
 import parquet.hadoop.util.ContextUtil
 import parquet.schema.MessageTypeParser
 
+import org.apache.hadoop.fs.{FileSystem, Path}
+import org.apache.hadoop.mapreduce.Job
 import org.apache.spark.SparkContext
 import org.apache.spark.sql._
+import org.apache.spark.sql.catalyst.{SqlLexical, SqlParser}
+import org.apache.spark.sql.catalyst.analysis.{Star, UnresolvedAttribute}
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.types.{BooleanType, IntegerType}
-import org.apache.spark.sql.test.TestSQLContext
-import org.apache.spark.sql.TestData
-import org.apache.spark.sql.SchemaRDD
 import org.apache.spark.sql.catalyst.util.getTempFilePath
-import org.apache.spark.sql.catalyst.{SqlLexical, SqlParser}
-import org.apache.spark.sql.catalyst.analysis.{UnresolvedAttribute, Star}
+import org.apache.spark.sql.test.TestSQLContext
+import org.apache.spark.sql.test.TestSQLContext._
 import org.apache.spark.util.Utils
 
-// Implicits
-import org.apache.spark.sql.test.TestSQLContext._
 
 case class TestRDDEntry(key: Int, value: String)
 
@@ -72,7 +68,6 @@ case class AllDataTypes(
     booleanField: Boolean)
 
 class ParquetQuerySuite extends QueryTest with FunSuiteLike with BeforeAndAfterAll {
-  import TestData._
   TestData // Load test data tables.
 
   var testRDD: SchemaRDD = null
@@ -319,7 +314,7 @@ class ParquetQuerySuite extends QueryTest with FunSuiteLike with BeforeAndAfterA
 
   test("create RecordFilter for simple predicates") {
     val attribute1 = new AttributeReference("first", IntegerType, false)()
-    val predicate1 = new Equals(attribute1, new Literal(1, IntegerType))
+    val predicate1 = new EqualTo(attribute1, new Literal(1, IntegerType))
     val filter1 = ParquetFilters.createFilter(predicate1)
     assert(filter1.isDefined)
     assert(filter1.get.predicate == predicate1, "predicates do not match")
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala
index df761b073a..ec653efcc8 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala
@@ -698,7 +698,7 @@ private[hive] object HiveQl {
 
       val joinConditions = joinExpressions.sliding(2).map {
         case Seq(c1, c2) =>
-          val predicates = (c1, c2).zipped.map { case (e1, e2) => Equals(e1, e2): Expression }
+          val predicates = (c1, c2).zipped.map { case (e1, e2) => EqualTo(e1, e2): Expression }
           predicates.reduceLeft(And)
       }.toBuffer
 
@@ -924,9 +924,9 @@ private[hive] object HiveQl {
     case Token("%", left :: right:: Nil) => Remainder(nodeToExpr(left), nodeToExpr(right))
 
     /* Comparisons */
-    case Token("=", left :: right:: Nil) => Equals(nodeToExpr(left), nodeToExpr(right))
-    case Token("!=", left :: right:: Nil) => Not(Equals(nodeToExpr(left), nodeToExpr(right)))
-    case Token("<>", left :: right:: Nil) => Not(Equals(nodeToExpr(left), nodeToExpr(right)))
+    case Token("=", left :: right:: Nil) => EqualTo(nodeToExpr(left), nodeToExpr(right))
+    case Token("!=", left :: right:: Nil) => Not(EqualTo(nodeToExpr(left), nodeToExpr(right)))
+    case Token("<>", left :: right:: Nil) => Not(EqualTo(nodeToExpr(left), nodeToExpr(right)))
     case Token(">", left :: right:: Nil) => GreaterThan(nodeToExpr(left), nodeToExpr(right))
     case Token(">=", left :: right:: Nil) => GreaterThanOrEqual(nodeToExpr(left), nodeToExpr(right))
     case Token("<", left :: right:: Nil) => LessThan(nodeToExpr(left), nodeToExpr(right))
@@ -966,7 +966,7 @@ private[hive] object HiveQl {
           // FIXME (SPARK-2155): the key will get evaluated for multiple times in CaseWhen's eval().
           // Hence effectful / non-deterministic key expressions are *not* supported at the moment.
           // We should consider adding new Expressions to get around this.
-          Seq(Equals(nodeToExpr(branches(0)), nodeToExpr(condVal)),
+          Seq(EqualTo(nodeToExpr(branches(0)), nodeToExpr(condVal)),
               nodeToExpr(value))
         case Seq(elseVal) => Seq(nodeToExpr(elseVal))
       }.toSeq.reduce(_ ++ _)
diff --git a/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveTypeCoercionSuite.scala b/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveTypeCoercionSuite.scala
index cc8744c966..7436de264a 100644
--- a/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveTypeCoercionSuite.scala
+++ b/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveTypeCoercionSuite.scala
@@ -17,7 +17,7 @@
 
 package org.apache.spark.sql.hive.execution
 
-import org.apache.spark.sql.catalyst.expressions.{Cast, Equals}
+import org.apache.spark.sql.catalyst.expressions.{Cast, EqualTo}
 import org.apache.spark.sql.execution.Project
 import org.apache.spark.sql.hive.test.TestHive
 
@@ -39,13 +39,13 @@ class HiveTypeCoercionSuite extends HiveComparisonTest {
 
     // No cast expression introduced
     project.transformAllExpressions { case c: Cast =>
-      assert(false, "unexpected cast " + c)
+      fail(s"unexpected cast $c")
       c
     }
 
-    // Only one Equals
+    // Only one equality check
     var numEquals = 0
-    project.transformAllExpressions { case e: Equals =>
+    project.transformAllExpressions { case e: EqualTo =>
       numEquals += 1
       e
     }