[GitHub] [spark] srowen commented on a diff in pull request #36457: [SPARK-39107][SQL] Account for empty string input in regex replace

[GitBox <gi...@apache.org>]

srowen commented on code in PR #36457:
URL: https://github.com/apache/spark/pull/36457#discussion_r866464610


##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/regexpExpressions.scala:
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@@ -642,7 +642,7 @@ case class RegExpReplace(subject: Expression, regexp: Expression, rep: Expressio
     }
     val source = s.toString()
     val position = i.asInstanceOf[Int] - 1
-    if (position < source.length) {
+    if (position < source.length || (position == 0 && source.equals(""))) {

Review Comment:
   This is minor, but check `source.length == 0` instead? faster.
   In fact, isn't this equivalent to `position == 0 || position < source.length`?



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