[DOCS] Clarify round mode for format_number & round functions

## What changes were proposed in this pull request?

Updated the description for the `format_number` description to indicate that it uses `HALF_EVEN` rounding. Updated the description for the `round` description to indicate that it uses `HALF_UP` rounding.

## How was this patch tested?

Just changing the two function comments so no testing involved.

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: Roxanne Moslehi <rmoslehi@palantir.com>
Author: roxannemoslehi <rmoslehi@berkeley.edu>

Closes #17399 from roxannemoslehi/patch-1.

1 files changed, 5 insertions, 5 deletions

diff --git a/sql/core/src/main/scala/org/apache/spark/sql/functions.scala b/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
index 66bb8816a6..acdb8e2d3e 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
@@ -1861,7 +1861,7 @@ object functions {
   def rint(columnName: String): Column = rint(Column(columnName))
 
   /**
-   * Returns the value of the column `e` rounded to 0 decimal places.
+   * Returns the value of the column `e` rounded to 0 decimal places with HALF_UP round mode.
    *
    * @group math_funcs
    * @since 1.5.0
@@ -1869,8 +1869,8 @@ object functions {
   def round(e: Column): Column = round(e, 0)
 
   /**
-   * Round the value of `e` to `scale` decimal places if `scale` is greater than or equal to 0
-   * or at integral part when `scale` is less than 0.
+   * Round the value of `e` to `scale` decimal places with HALF_UP round mode
+   * if `scale` is greater than or equal to 0 or at integral part when `scale` is less than 0.
    *
    * @group math_funcs
    * @since 1.5.0
@@ -2191,8 +2191,8 @@ object functions {
   }
 
   /**
-   * Formats numeric column x to a format like '#,###,###.##', rounded to d decimal places,
-   * and returns the result as a string column.
+   * Formats numeric column x to a format like '#,###,###.##', rounded to d decimal places
+   * with HALF_EVEN round mode, and returns the result as a string column.
    *
    * If d is 0, the result has no decimal point or fractional part.
    * If d is less than 0, the result will be null.