[SPARK-7286][SQL] Deprecate !== in favour of =!=

This PR replaces #9925 which had issues with CI. **Please see the original PR for any previous discussions.**

## What changes were proposed in this pull request?
Deprecate the SparkSQL column operator !== and use =!= as an alternative.
Fixes subtle issues related to operator precedence (basically, !== does not have the same priority as its logical negation, ===).

## How was this patch tested?
All currently existing tests.

Author: Jakob Odersky <jodersky@gmail.com>

Closes #11588 from jodersky/SPARK-7286.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/dsl/package.scala

@@ -83,7 +83,7 @@ package object dsl {
     def >= (other: Expression): Predicate = GreaterThanOrEqual(expr, other)
     def === (other: Expression): Predicate = EqualTo(expr, other)
     def <=> (other: Expression): Predicate = EqualNullSafe(expr, other)
-    def !== (other: Expression): Predicate = Not(EqualTo(expr, other))
+    def =!= (other: Expression): Predicate = Not(EqualTo(expr, other))
 
     def in(list: Expression*): Expression = In(expr, list)
 

sql/core/src/main/scala/org/apache/spark/sql/Column.scala

@@ -253,6 +253,23 @@ class Column(protected[sql] val expr: Expression) extends Logging {
    */
   def equalTo(other: Any): Column = this === other
 
+  /**
+   * Inequality test.
+   * {{{
+   *   // Scala:
+   *   df.select( df("colA") =!= df("colB") )
+   *   df.select( !(df("colA") === df("colB")) )
+   *
+   *   // Java:
+   *   import static org.apache.spark.sql.functions.*;
+   *   df.filter( col("colA").notEqual(col("colB")) );
+   * }}}
+   *
+   * @group expr_ops
+   * @since 2.0.0
+    */
+  def =!= (other: Any): Column = withExpr{ Not(EqualTo(expr, lit(other).expr)) }
+
   /**
    * Inequality test.
    * {{{
@@ -267,8 +284,9 @@ class Column(protected[sql] val expr: Expression) extends Logging {
    *
    * @group expr_ops
    * @since 1.3.0
-   */
-  def !== (other: Any): Column = withExpr{ Not(EqualTo(expr, lit(other).expr)) }
+    */
+  @deprecated("!== does not have the same precedence as ===, use =!= instead", "2.0.0")
+  def !== (other: Any): Column = this =!= other
 
   /**
    * Inequality test.

sql/core/src/test/scala/org/apache/spark/sql/ColumnExpressionSuite.scala

@@ -349,7 +349,7 @@ class ColumnExpressionSuite extends QueryTest with SharedSQLContext {
       testData2.collect().toSeq.filter(r => r.getInt(0) == r.getInt(1)))
   }
 
-  test("!==") {
+  test("=!=") {
     val nullData = sqlContext.createDataFrame(sparkContext.parallelize(
       Row(1, 1) ::
       Row(1, 2) ::

sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala

@@ -347,7 +347,7 @@ class JoinSuite extends QueryTest with SharedSQLContext {
         Row(null, null, 6, "F") :: Nil)
 
     checkAnswer(
-      left.join(right, ($"left.N" === $"right.N") && ($"left.N" !== 3), "full"),
+      left.join(right, ($"left.N" === $"right.N") && ($"left.N" =!= 3), "full"),
       Row(1, "A", null, null) ::
         Row(2, "B", null, null) ::
         Row(3, "C", null, null) ::
@@ -357,7 +357,7 @@ class JoinSuite extends QueryTest with SharedSQLContext {
         Row(null, null, 6, "F") :: Nil)
 
     checkAnswer(
-      left.join(right, ($"left.N" === $"right.N") && ($"right.N" !== 3), "full"),
+      left.join(right, ($"left.N" === $"right.N") && ($"right.N" =!= 3), "full"),
       Row(1, "A", null, null) ::
         Row(2, "B", null, null) ::
         Row(3, "C", null, null) ::

sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetFilterSuite.scala

@@ -120,7 +120,7 @@ class ParquetFilterSuite extends QueryTest with ParquetTest with SharedSQLContex
 
       checkFilterPredicate('_1 === true, classOf[Eq[_]], true)
       checkFilterPredicate('_1 <=> true, classOf[Eq[_]], true)
-      checkFilterPredicate('_1 !== true, classOf[NotEq[_]], false)
+      checkFilterPredicate('_1 =!= true, classOf[NotEq[_]], false)
     }
   }
 
@@ -131,7 +131,7 @@ class ParquetFilterSuite extends QueryTest with ParquetTest with SharedSQLContex
 
       checkFilterPredicate('_1 === 1, classOf[Eq[_]], 1)
       checkFilterPredicate('_1 <=> 1, classOf[Eq[_]], 1)
-      checkFilterPredicate('_1 !== 1, classOf[NotEq[_]], (2 to 4).map(Row.apply(_)))
+      checkFilterPredicate('_1 =!= 1, classOf[NotEq[_]], (2 to 4).map(Row.apply(_)))
 
       checkFilterPredicate('_1 < 2, classOf[Lt[_]], 1)
       checkFilterPredicate('_1 > 3, classOf[Gt[_]], 4)
@@ -157,7 +157,7 @@ class ParquetFilterSuite extends QueryTest with ParquetTest with SharedSQLContex
 
       checkFilterPredicate('_1 === 1, classOf[Eq[_]], 1)
       checkFilterPredicate('_1 <=> 1, classOf[Eq[_]], 1)
-      checkFilterPredicate('_1 !== 1, classOf[NotEq[_]], (2 to 4).map(Row.apply(_)))
+      checkFilterPredicate('_1 =!= 1, classOf[NotEq[_]], (2 to 4).map(Row.apply(_)))
 
       checkFilterPredicate('_1 < 2, classOf[Lt[_]], 1)
       checkFilterPredicate('_1 > 3, classOf[Gt[_]], 4)
@@ -183,7 +183,7 @@ class ParquetFilterSuite extends QueryTest with ParquetTest with SharedSQLContex
 
       checkFilterPredicate('_1 === 1, classOf[Eq[_]], 1)
       checkFilterPredicate('_1 <=> 1, classOf[Eq[_]], 1)
-      checkFilterPredicate('_1 !== 1, classOf[NotEq[_]], (2 to 4).map(Row.apply(_)))
+      checkFilterPredicate('_1 =!= 1, classOf[NotEq[_]], (2 to 4).map(Row.apply(_)))
 
       checkFilterPredicate('_1 < 2, classOf[Lt[_]], 1)
       checkFilterPredicate('_1 > 3, classOf[Gt[_]], 4)
@@ -209,7 +209,7 @@ class ParquetFilterSuite extends QueryTest with ParquetTest with SharedSQLContex
 
       checkFilterPredicate('_1 === 1, classOf[Eq[_]], 1)
       checkFilterPredicate('_1 <=> 1, classOf[Eq[_]], 1)
-      checkFilterPredicate('_1 !== 1, classOf[NotEq[_]], (2 to 4).map(Row.apply(_)))
+      checkFilterPredicate('_1 =!= 1, classOf[NotEq[_]], (2 to 4).map(Row.apply(_)))
 
       checkFilterPredicate('_1 < 2, classOf[Lt[_]], 1)
       checkFilterPredicate('_1 > 3, classOf[Gt[_]], 4)
@@ -238,7 +238,7 @@ class ParquetFilterSuite extends QueryTest with ParquetTest with SharedSQLContex
       checkFilterPredicate('_1 === "1", classOf[Eq[_]], "1")
       checkFilterPredicate('_1 <=> "1", classOf[Eq[_]], "1")
       checkFilterPredicate(
-        '_1 !== "1", classOf[NotEq[_]], (2 to 4).map(i => Row.apply(i.toString)))
+        '_1 =!= "1", classOf[NotEq[_]], (2 to 4).map(i => Row.apply(i.toString)))
 
       checkFilterPredicate('_1 < "2", classOf[Lt[_]], "1")
       checkFilterPredicate('_1 > "3", classOf[Gt[_]], "4")
@@ -272,7 +272,7 @@ class ParquetFilterSuite extends QueryTest with ParquetTest with SharedSQLContex
         '_1.isNotNull, classOf[NotEq[_]], (1 to 4).map(i => Row.apply(i.b)).toSeq)
 
       checkBinaryFilterPredicate(
-        '_1 !== 1.b, classOf[NotEq[_]], (2 to 4).map(i => Row.apply(i.b)).toSeq)
+        '_1 =!= 1.b, classOf[NotEq[_]], (2 to 4).map(i => Row.apply(i.b)).toSeq)
 
       checkBinaryFilterPredicate('_1 < 2.b, classOf[Lt[_]], 1.b)
       checkBinaryFilterPredicate('_1 > 3.b, classOf[Gt[_]], 4.b)

sql/hive/src/test/scala/org/apache/spark/sql/hive/ExpressionSQLBuilderSuite.scala

@@ -47,7 +47,7 @@ class ExpressionSQLBuilderSuite extends SQLBuilderTest {
   test("binary comparisons") {
     checkSQL('a.int === 'b.int, "(`a` = `b`)")
     checkSQL('a.int <=> 'b.int, "(`a` <=> `b`)")
-    checkSQL('a.int !== 'b.int, "(NOT (`a` = `b`))")
+    checkSQL('a.int =!= 'b.int, "(NOT (`a` = `b`))")
 
     checkSQL('a.int < 'b.int, "(`a` < `b`)")
     checkSQL('a.int <= 'b.int, "(`a` <= `b`)")

sql/hive/src/test/scala/org/apache/spark/sql/hive/orc/OrcFilterSuite.scala

@@ -211,7 +211,7 @@ class OrcFilterSuite extends QueryTest with OrcTest {
           |expr = (not leaf-0)""".stripMargin.trim
       )
       checkFilterPredicate(
-        '_1 !== 1,
+        '_1 =!= 1,
         """leaf-0 = (EQUALS _1 1)
           |expr = (not leaf-0)""".stripMargin.trim
       )