Github user viirya commented on a diff in the pull request:
https://github.com/apache/spark/pull/18106#discussion_r123757175
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/misc.scala
---
@@ -132,3 +133,154 @@ case class Uuid() extends LeafExpression {
s"UTF8String.fromString(java.util.UUID.randomUUID().toString());",
isNull = "false")
}
}
+
+/**
+ * Returns date truncated to the unit specified by the format or
+ * numeric truncated to scale decimal places.
+ */
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+ usage = """
+ _FUNC_(data[, fmt]) - Returns `data` truncated by the format model
`fmt`.
+ If `data` is DateType, returns `data` with the time portion of the
day truncated to the unit specified by the format model `fmt`.
+ If `data` is DecimalType/DoubleType, returns `data` truncated to
`fmt` decimal places.
+ """,
+ extended = """
+ Examples:
+ > SELECT _FUNC_('2009-02-12', 'MM');
+ 2009-02-01.
+ > SELECT _FUNC_('2015-10-27', 'YEAR');
+ 2015-01-01
+ > SELECT _FUNC_('1989-03-13');
+ 1989-03-01
+ > SELECT _FUNC_(1234567891.1234567891, 4);
+ 1234567891.1234
+ > SELECT _FUNC_(1234567891.1234567891, -4);
+ 1234560000
+ > SELECT _FUNC_(1234567891.1234567891);
+ 1234567891
+ """)
+// scalastyle:on line.size.limit
+case class Trunc(data: Expression, format: Expression)
+ extends BinaryExpression with ExpectsInputTypes {
+
+ def this(data: Expression) = {
+ this(data, Literal(if (data.dataType.isInstanceOf[DateType]) "MM" else
0))
+ }
+
+ override def left: Expression = data
+ override def right: Expression = format
+
+ override def dataType: DataType = data.dataType
+
+ override def inputTypes: Seq[AbstractDataType] = dataType match {
+ case NullType => Seq(dataType, TypeCollection(StringType, IntegerType))
+ case DateType => Seq(dataType, StringType)
+ case DoubleType | DecimalType.Fixed(_, _) => Seq(dataType, IntegerType)
+ case _ => Seq(TypeCollection(DateType, DoubleType, DecimalType),
+ TypeCollection(StringType, IntegerType))
+ }
+
+ override def nullable: Boolean = true
+
+ override def prettyName: String = "trunc"
+
+ private val isTruncNumber =
+ (dataType.isInstanceOf[DoubleType] ||
dataType.isInstanceOf[DecimalType]) &&
+ format.dataType.isInstanceOf[IntegerType]
--- End diff --
Combined with this and `inputTypes`, once we have input types like
(DoubleType, StringType), looks like `eval` simply return null. Seems to me
it's not considered as correct result.
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