Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/16893#discussion_r100707748
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/StringUtils.scala
---
@@ -27,21 +28,28 @@ object StringUtils {
// replace the % with .*, match 0 or more times with any character
def escapeLikeRegex(v: String): String = {
--- End diff --
Actually, I'm wrong: we can't quite do that simplification because the old
code has a subtle bug related to backslash-escaping. Due to the complexity and
terseness the old implementation, it's a little non-obvious to spot that the
`case (prev, '\\') => ""` has the effect of always ignoring backslash
characters, so this method is incapable of producing a backslash in its output.
This is a problem if the user wants to write a `LIKE` pattern to match
backslashes then this is impossible with the current code.
It turns out that this is covered by #15398, which also implements
performance improvements for this code, so I guess this PR and JIRA is
redundant :(
I thought #15398 had been merged / fixed by now, but I guess not.
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