[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.

(cherry picked from commit 2f6a835e1a039a0b1ba6e184b3350444b70f91df)
Signed-off-by: Reynold Xin <rxin@apache.org>

7 files changed, 20 insertions, 17 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,