Github user liancheng commented on a diff in the pull request:
https://github.com/apache/spark/pull/2908#discussion_r19284542
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringOperations.scala
---
@@ -103,21 +103,21 @@ case class Like(left: Expression, right: Expression)
// replace the _ with .{1} exactly match 1 time of any character
// replace the % with .*, match 0 or more times with any character
override def escape(v: String) = {
- val sb = new StringBuilder()
- var i = 0;
+ val sb = new StringBuilder("""(?s)""")
+ var i = 0
while (i < v.length) {
// Make a special case for "\\_" and "\\%"
- val n = v.charAt(i);
+ val n = v.charAt(i)
if (n == '\\' && i + 1 < v.length && (v.charAt(i + 1) == '_' ||
v.charAt(i + 1) == '%')) {
sb.append(v.charAt(i + 1))
i += 1
} else {
if (n == '_') {
- sb.append(".");
+ sb.append(".")
} else if (n == '%') {
- sb.append(".*");
+ sb.append(".*")
} else {
- sb.append(Pattern.quote(Character.toString(n)));
+ sb.append(Pattern.quote(Character.toString(n)))
}
}
--- End diff --
I feel a little complicated about this... This function is not on critical
path, so I'd like to refactor it in a more functional and readable (but less
efficient) way, for example:
```scala
override def escape(v: String) = "(?s)" + (' ' +: v.init).zip(v).flatMap {
case (prefix, '_') => if (prefix == '\\') "_" else "."
case (prefix, '%') => if (prefix == '\\') "%" else ".*"
case (_, ch) => Character.toString(ch)
}.mkString
```
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