Fix regexp_replace no-op when '+' is the only metacharacter

- Add the missing '+' to regex special characters.
- Add unit and integration coverage for the '+'-only case.

Signed-off-by: Igor Peshansky <ipeshansky@nvidia.com>

Author: igorpeshansky

integration_tests/src/main/python/regexp_test.py

@@ -309,6 +309,7 @@ def test_re_replace_repetition():
                 'REGEXP_REPLACE(a, "A{0,}", "PROD")',
                 'REGEXP_REPLACE(a, "T?E?", "PROD")',
                 'REGEXP_REPLACE(a, "A*", "PROD")',
+                'REGEXP_REPLACE(a, "A+", "PROD")',
                 'REGEXP_REPLACE(a, "A{0,5}", "PROD")',
                 'REGEXP_REPLACE(a, "(A*)", "PROD")',
                 'REGEXP_REPLACE(a, "(((A*)))", "PROD")',

sql-plugin/src/main/scala/com/nvidia/spark/rapids/GpuOverrides.scala

@@ -469,7 +469,7 @@ object GpuOverrides extends Logging {
   private[this] lazy val regexList: Seq[String] = Seq("\\", "\u0000", "\\x", "\t", "\n", "\r",
     "\f", "\\a", "\\e", "\\cx", "[", "]", "^", "&", ".", "*", "\\d", "\\D", "\\h", "\\H", "\\s",
     "\\S", "\\v", "\\V", "\\w", "\\w", "\\p", "$", "\\b", "\\B", "\\A", "\\G", "\\Z", "\\z", "\\R",
-    "?", "|", "(", ")", "{", "}", "\\k", "\\Q", "\\E", ":", "!", "<=", ">")
+    "?", "+", "|", "(", ")", "{", "}", "\\k", "\\Q", "\\E", ":", "!", "<=", ">")
   val regexMetaChars = ".$^[]\\|?*+(){}"
   /**
    * Provides a way to log an info message about how long an operation took in milliseconds.

tests/src/test/scala/com/nvidia/spark/rapids/StringFunctionSuite.scala

@@ -324,6 +324,18 @@ class RegExpUtilsSuite extends AnyFunSuite {
     assert(conv2 == open + "1}3",
       s"expected user `$$13` to back off to `$${1}3`, got `$conv2`")
   }
+
+  test("isSupportedStringReplacePattern classifies regex patterns correctly") {
+    val cases = Seq(
+      "A" -> true,
+      "A*" -> false,
+      "(A)" -> false,
+      "A+" -> false)
+
+    cases.foreach { case (pattern, expected) =>
+      assert(GpuOverrides.isSupportedStringReplacePattern(pattern) == expected)
+    }
+  }
 }
 
 /*