Github user kevinyu98 commented on a diff in the pull request:
https://github.com/apache/spark/pull/12646#discussion_r116914922
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala
---
@@ -461,68 +462,249 @@ 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 trim the spaces or a trim string from both ends for 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
side of the string
+ LEADING, FROM - these are keyword to specify for trim string from
left side of the string
+ TRAILING, FROM - these are keyword to specify for trim string from
right side 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])
--- End diff --
I think we need to overwrite the nullSafeCodeGen from BinaryExpression, it
will be the right.genCode(ctx), I am not sure it will be able to check the
NonEmpty or not.
Also I remembered there is another place we need to make hack changes if we
use binaryExpression, it is at visitFunctionCall in AstBuilder.scala, for the
existing trim() function, the arguments will be built with one expression, but
the trim function registered with two expressions, so I have to create one more
default expression for the trim() function, otherwise, it will fail at
Analyzer.scala with this failure
case Failure(e) =>
throw new AnalysisException(s"Invalid number of arguments for function
$name")
based on the above, I chose the Seq(expressions)
> StringTrim has a sequence of children (one or two children in our case),
so you can't make sure it's unary
yes
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