cloud-fan commented on code in PR #57476:
URL: https://github.com/apache/spark/pull/57476#discussion_r3746490229
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/mathExpressions.scala:
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@@ -1971,6 +1971,51 @@ case class BRound(
newLeft: Expression, newRight: Expression): BRound = copy(child = newLeft,
scale = newRight)
}
+/**
+ * Truncate an expression toward zero to `scale` decimal places.
+ * A negative `scale` truncates digits to the left of the decimal point.
+ * truncate(1234.5678, 2) = 1234.56, truncate(-1234.5678, 2) = -1234.56.
+ */
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+ usage = "_FUNC_(expr[, scale]) - Returns `expr` truncated toward zero to
`scale` decimal places. `scale` defaults to 0. A negative `scale` truncates
digits to the left of the decimal point.",
+ arguments = """
+ Arguments:
+ * expr - The expression to truncate. An expression that evaluates to a
numeric.
+ * scale - The number of decimal places to keep. An expression that
evaluates to an integer, must be a constant, and defaults to 0. A negative
value truncates digits to the left of the decimal point.
Review Comment:
```suggestion
* scale - The number of decimal places to keep. It must be a constant
integer expression and defaults to 0. A negative value truncates digits to the
left of the decimal point.
```
##########
sql/api/src/main/scala/org/apache/spark/sql/functions.scala:
##########
@@ -6069,6 +6069,50 @@ object functions {
*/
def round(e: Column, scale: Column): Column = Column.fn("round", e, scale)
+ /**
+ * Truncates the value of `e` toward zero to 0 decimal places.
+ *
+ * @param e
+ * the value to truncate. A column that evaluates to a numeric.
+ * @return
+ * Returns a column of the same type as the input.
Review Comment:
Decimal inputs do not necessarily keep the same Spark SQL type: `RoundBase`
derives new precision and scale from the requested scale. Please mirror the
Python wording here and in the other two overloads: the type is preserved
except that decimal precision and scale may change.
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