Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/22227#discussion_r214135400
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/regexpExpressions.scala
---
@@ -229,33 +229,58 @@ case class RLike(left: Expression, right: Expression)
extends StringRegexExpress
/**
- * Splits str around pat (pattern is a regular expression).
+ * Splits str around matches of the given regex.
*/
@ExpressionDescription(
- usage = "_FUNC_(str, regex) - Splits `str` around occurrences that match
`regex`.",
+ usage = "_FUNC_(str, regex, limit) - Splits `str` around occurrences
that match `regex`" +
+ " and returns an array of at most `limit`",
+ arguments = """
+ Arguments:
+ * str - a string expression to split.
+ * regex - a string representing a regular expression. The regex
string should be a
+ Java regular expression.
+ * limit - an integer expression which controls the number of times
the regex is applied.
+
+ limit > 0: The resulting array's length will not be more than
`limit`, and the resulting
+ array's last entry will contain all input beyond the
last matched regex.
+
+ limit < 0: `regex` will be applied as many times as possible, and
the resulting
+ array can be of any size.
+
+ limit = 0: `regex` will be applied as many times as possible, the
resulting array can
--- End diff --
yea but i'd focus on what behavior we want to enable. do other database
systems have this split=0 semantics? if not, i'd rewrite split=0 internally to
just -1.
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