Github user wzhfy commented on a diff in the pull request:
https://github.com/apache/spark/pull/12646#discussion_r116924283
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala
---
@@ -461,68 +462,246 @@ 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 trims leading or trailing characters (or both) from the
specified 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 trimString FROM str) - Remove the leading and trailing
trimString from `str`
+ _FUNC_(LEADING trimChar FROM str) - Remove the leading trimString from
`str`
+ _FUNC_(TRAILING trimChar FROM str) - Remove the trailing trimString
from `str`
+ """,
extended = """
+ Arguments:
+ str - a string expression
+ trimString - the trim string
+ BOTH, FROM - these are keyword to specify for trim string from both
ends of the string
+ LEADING, FROM - these are keyword to specify for trim string from
left end of the string
+ TRAILING, FROM - these are keyword to specify for trim string from
right end of the string
Examples:
> SELECT _FUNC_(' SparkSQL ');
SparkSQL
+ > SELECT _FUNC_(BOTH 'SL' FROM 'SSparkSQLS');
+ parkSQ
+ > SELECT _FUNC_(LEADING 'paS' FROM 'SSparkSQLS');
+ rkSQLS
+ > SELECT _FUNC_(TRAILING 'SLQ' FROM 'SSparkSQLS');
+ SSparkS
""")
-case class StringTrim(child: Expression)
- extends UnaryExpression with String2StringExpression {
+case class StringTrim(children: Seq[Expression])
+ extends Expression with ImplicitCastInputTypes {
+
+ require(children.size <= 2 && children.nonEmpty,
+ s"$prettyName requires at least one argument and no more than two.")
+
+ override def dataType: DataType = StringType
+ override def inputTypes: Seq[AbstractDataType] =
Seq.fill(children.size)(StringType)
- def convert(v: UTF8String): UTF8String = v.trim()
+ override def nullable: Boolean = children.exists(_.nullable)
+ override def foldable: Boolean = children.forall(_.foldable)
override def prettyName: String = "trim"
+ override def eval(input: InternalRow): Any = {
+ val inputs = children.map(_.eval(input).asInstanceOf[UTF8String])
+ if (inputs(0) != null) {
--- End diff --
Could you add a comment here for `inputs(0)` and `inputs(1)`, they may be a
little unclear to readers.
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