Re: [PR] Fix `regex` cache on pattern, less alloc, hash less often [datafusion]

[via GitHub]

Dimchikkk commented on code in PR #13414:
URL: https://github.com/apache/datafusion/pull/13414#discussion_r1842910817


##########
datafusion/functions/src/regex/regexpcount.rs:
##########
@@ -548,16 +549,22 @@ where
     }
 }
 
-fn compile_and_cache_regex<'a>(
-    regex: &'a str,
-    flags: Option<&'a str>,
-    regex_cache: &'a mut HashMap<String, Regex>,
-) -> Result<&'a Regex, ArrowError> {
-    if !regex_cache.contains_key(regex) {

Review Comment:
   yep,
   
    so without this fix the test fails with counting middle value to 0 instead 
of 1:
   ```rs
           let values = A::from(vec!["aaa", "Aaa", "aaa"]);
           let regex = A::from(vec!["aaa", "aaa", "aaa"]);
           let start = Int64Array::from(vec![1, 1, 1]);
           let flags = A::from(vec!["", "i", ""]);
   
           let expected = Int64Array::from(vec![1, 1, 1]);
   
           let re = regexp_count_func(&[
               Arc::new(values),
               Arc::new(regex),
               Arc::new(start),
               Arc::new(flags),
           ])
           .unwrap();
           assert_eq!(re.as_ref(), &expected);
    ```
    notice regex are different only by flags, so cache has 2 regex after this 
fix and only 1 before the fix.
   



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