address comments for #7805

Author: Davies Liu

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

@@ -710,7 +710,7 @@ case class ToDate(child: Expression) extends UnaryExpression with ImplicitCastIn
   override def eval(input: InternalRow): Any = child.eval(input)
 
   override def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode): String = {
-    defineCodeGen(ctx, ev, d => d)
+    child.genCode(ctx, ev)
   }
 }
 
@@ -726,23 +726,23 @@ case class TruncDate(date: Expression, format: Expression)
   override def dataType: DataType = DateType
   override def prettyName: String = "trunc"
 
-  lazy val minItemConst = DateTimeUtils.parseTruncLevel(format.eval().asInstanceOf[UTF8String])
+  private lazy val truncLevel = DateTimeUtils.parseTruncLevel(format.eval().asInstanceOf[UTF8String])
 
   override def eval(input: InternalRow): Any = {
-    val minItem = if (format.foldable) {
-      minItemConst
+    val level = if (format.foldable) {
+      truncLevel
     } else {
       DateTimeUtils.parseTruncLevel(format.eval().asInstanceOf[UTF8String])
     }
-    if (minItem == -1) {
+    if (level == -1) {
       // unknown format
       null
     } else {
       val d = date.eval(input)
       if (d == null) {
         null
       } else {
-        DateTimeUtils.truncDate(d.asInstanceOf[Int], minItem)
+        DateTimeUtils.truncDate(d.asInstanceOf[Int], level)
       }
     }
   }
@@ -751,7 +751,7 @@ case class TruncDate(date: Expression, format: Expression)
     val dtu = DateTimeUtils.getClass.getName.stripSuffix("$")
 
     if (format.foldable) {
-      if (minItemConst == -1) {
+      if (truncLevel == -1) {
         s"""
           boolean ${ev.isNull} = true;
           ${ctx.javaType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
@@ -763,7 +763,7 @@ case class TruncDate(date: Expression, format: Expression)
           boolean ${ev.isNull} = ${d.isNull};
           ${ctx.javaType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
           if (!${ev.isNull}) {
-            ${ev.primitive} = $dtu.truncDate(${d.primitive}, $minItemConst);
+            ${ev.primitive} = $dtu.truncDate(${d.primitive}, $truncLevel);
           }
         """
       }

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala

@@ -794,7 +794,8 @@ object DateTimeUtils {
     } else if (level == TRUNC_TO_MONTH) {
       d - DateTimeUtils.getDayOfMonth(d) + 1
     } else {
-      throw new Exception(s"Invalid trunc level: $level")
+      // caller make sure that this should never be reached
+      sys.error(s"Invalid trunc level: $level")
     }
   }
 

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

@@ -363,7 +363,7 @@ class DateExpressionsSuite extends SparkFunSuite with ExpressionEvalHelper {
       checkEvaluation(TruncDate(Literal.create(input, DateType), Literal.create(fmt, StringType)),
         expected)
       checkEvaluation(
-        TruncDate(Literal.create(input, DateType), NonFoldableLiteral.create(fmt, StringType)),
+        TruncDate(Literal.create(input, DateType), NonFoldableLiteral(fmt, StringType)),
         expected)
     }
     val date = Date.valueOf("2015-07-22")

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

@@ -47,8 +47,4 @@ object NonFoldableLiteral {
     val lit = Literal(value)
     NonFoldableLiteral(lit.value, lit.dataType)
   }
-  def create(value: Any, dataType: DataType): NonFoldableLiteral = {
-    val lit = Literal.create(value, dataType)
-    NonFoldableLiteral(lit.value, lit.dataType)
-  }
 }

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

@@ -192,13 +192,13 @@ class StringExpressionsSuite extends SparkFunSuite with ExpressionEvalHelper {
     checkEvaluation(Literal.create("a", StringType).like(Literal.create(null, StringType)), null)
     checkEvaluation(Literal.create(null, StringType).like(Literal.create(null, StringType)), null)
     checkEvaluation(
-      Literal.create("a", StringType).like(NonFoldableLiteral.create("a", StringType)), true)
+      Literal.create("a", StringType).like(NonFoldableLiteral("a", StringType)), true)
     checkEvaluation(
-      Literal.create("a", StringType).like(NonFoldableLiteral.create(null, StringType)), null)
+      Literal.create("a", StringType).like(NonFoldableLiteral(null, StringType)), null)
     checkEvaluation(
-      Literal.create(null, StringType).like(NonFoldableLiteral.create("a", StringType)), null)
+      Literal.create(null, StringType).like(NonFoldableLiteral("a", StringType)), null)
     checkEvaluation(
-      Literal.create(null, StringType).like(NonFoldableLiteral.create(null, StringType)), null)
+      Literal.create(null, StringType).like(NonFoldableLiteral(null, StringType)), null)
 
     checkEvaluation("abdef" like "abdef", true)
     checkEvaluation("a_%b" like "a\\__b", true)
@@ -241,12 +241,12 @@ class StringExpressionsSuite extends SparkFunSuite with ExpressionEvalHelper {
     checkEvaluation(Literal.create(null, StringType) rlike "abdef", null)
     checkEvaluation("abdef" rlike Literal.create(null, StringType), null)
     checkEvaluation(Literal.create(null, StringType) rlike Literal.create(null, StringType), null)
-    checkEvaluation("abdef" rlike NonFoldableLiteral.create("abdef", StringType), true)
-    checkEvaluation("abdef" rlike NonFoldableLiteral.create(null, StringType), null)
+    checkEvaluation("abdef" rlike NonFoldableLiteral("abdef", StringType), true)
+    checkEvaluation("abdef" rlike NonFoldableLiteral(null, StringType), null)
     checkEvaluation(
-      Literal.create(null, StringType) rlike NonFoldableLiteral.create("abdef", StringType), null)
+      Literal.create(null, StringType) rlike NonFoldableLiteral("abdef", StringType), null)
     checkEvaluation(
-      Literal.create(null, StringType) rlike NonFoldableLiteral.create(null, StringType), null)
+      Literal.create(null, StringType) rlike NonFoldableLiteral(null, StringType), null)
 
     checkEvaluation("abdef" rlike "abdef", true)
     checkEvaluation("abbbbc" rlike "a.*c", true)

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

@@ -2192,6 +2192,9 @@ object functions {
   /**
    * Returns date truncated to the unit specified by the format.
    *
+   * @param format: 'year', 'yyyy', 'yy' for truncate by year,
+   *               or 'month', 'mon', 'mm' for truncate by month
+   *
    * @group datetime_funcs
    * @since 1.5.0
    */