[GitHub] spark pull request #18106: [SPARK-20754][SQL] Support TRUNC (number)

[viirya <gi...@git.apache.org>]

Github user viirya commented on a diff in the pull request:

    https://github.com/apache/spark/pull/18106#discussion_r123155483
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/misc.scala ---
    @@ -132,3 +133,141 @@ 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 ImplicitCastInputTypes {
    +
    +  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
    +
    +  val isTruncNumber = format.dataType.isInstanceOf[IntegerType]
    +
    +  override def dataType: DataType = data.dataType
    +
    +  override def inputTypes: Seq[AbstractDataType] =
    +    Seq(TypeCollection(DateType, DoubleType, DecimalType),
    +      TypeCollection(StringType, IntegerType))
    --- End diff --
    
    I think this might lead to wrong input types combinations such as (DoubleType, StringType) and (DateType, IntegerType)?


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