Github user wzhfy commented on a diff in the pull request:
https://github.com/apache/spark/pull/12646#discussion_r118486380
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala
---
@@ -461,68 +462,269 @@ case class FindInSet(left: Expression, right:
Expression) extends BinaryExpressi
}
/**
- * A function that trim the spaces from both ends for the specified string.
- */
+ * A function that takes a character string, removes the leading and/or
trailing characters matching with the characters
+ * in the trim string, returns the new string. If LEADING/TRAILING/BOTH
and trimStr keywords are not specified, it
+ * defaults to remove space character from both ends.
+ * trimStr: A character string to be trimmed from the source string, if it
has multiple characters, the function
+ * searches for each character in the source string, removes the
characters from the source string until it
+ * encounters the first non-match character.
+ * LEADING: removes any characters from the left end of the source string
that matches characters in the trim string.
+ * TRAILING: removes any characters from the right end of the source
string that matches characters in the trim string.
+ * BOTH: removes any characters from both ends of the source string that
matches characters in the trim string.
+ */
@ExpressionDescription(
- usage = "_FUNC_(str) - Removes the leading and trailing space characters
from `str`.",
+ usage = """
+ _FUNC_(str) - Removes the leading and trailing space characters from
`str`.
+ _FUNC_(BOTH trimStr FROM str) - Remove the leading and trailing
trimString from `str`
--- End diff --
I'm a little confused. This function is only for "BOTH", right?
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