[GitHub] [arrow] kou commented on a diff in pull request #14579: ARROW-18235: [C++][Gandiva] Fix the like function implementation for escape chars

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

kou commented on code in PR #14579:
URL: https://github.com/apache/arrow/pull/14579#discussion_r1013369863


##########
cpp/src/gandiva/regex_util.cc:
##########
@@ -44,6 +45,10 @@ Status RegexUtil::SqlLikePatternToPcre(const std::string& sql_pattern, char esca
 
       cur = sql_pattern.at(idx);
       if (cur == '_' || cur == '%' || cur == escape_char) {
+        if (cur == '\\') {

Review Comment:
   Is this condition correct? It seems that we need to check whether the `cur` (== `escape_char`) is a special character or not:
   
   ```suggestion
           if (pcre_regex_specials_.find(cur) != pcre_regex_specials_.end()) {
   ```
   
   BTW, can we extract this condition to out of this `for` loop if my suggestion is correct?



##########
cpp/src/gandiva/tests/filter_test.cc:
##########
@@ -414,6 +414,39 @@ TEST_F(TestFilter, TestLike) {
 
   // Validate results
   EXPECT_ARROW_ARRAY_EQUALS(exp, selection_vector->ToArray());
+
+  auto literal_escape_pattern =
+      TreeExprBuilder::MakeStringLiteral("%tu^_security^_freeze%");
+  auto escape_char = TreeExprBuilder::MakeStringLiteral("^");

Review Comment:
   Can we use a PCRE special character that is invalid without suitable escap such as `[` instead?



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