Hi, this is a question regarding regex in detecting a file name pattern (not parsing of the contents).

In the app I work with we have logfiles with a simple format filename.log, then we have rollovers based on policy (size/age) that look like:  filename.log.2020-12-19.1 (last digit increments: 2,3,...999).  Obviously, the other digits are YYYY-MM-DD.

Using the website regex101 dot com, I created and tested my regex for the above rollover and it works correctly:
^[a-z].*\.log\.[0-9]{4}\-[0-9]{2}\-[0-9]{2}\.[0-9]{1,3}$

I don't believe ^ and $ are needed for a filename (maybe if it contains spaces??) but I tried with and without, and same result.  Auto-detect does not pickup the pattern in my parser mappings, and it goes to basic parser.  I know the workaround of going to "Parse With" but just curious, is it some kind of versioning with Regex?  Or does LVP use a subset of regex? 

Also, my parser args for the file content are, of course, the same for current log or the rollover. Would I be better off keeping one mapping and using a logical OR.  e.g  ( patternA | patternB)?

Feedback appreciated, thanks!