Filtered value comparisons

I can think of plenty of cases where the only significant characters in comparing two values are alphanumeric ones. Phone and credit card numbers, which can be embellished with optional brackets, dashes, and spaces, etc., are obvious examples.

Unfortunately MySQL (and I'm sure most other databases) don't have the regexp grunt to do those sorts of comparisons, so we will have to store our own converted values for any fields on which we want alphanumeric-only comparison, which will require our own table. This is overhead that has been so far avoided, but may help solve some other problems (eg. 🐛 Case sensitivity (uppercase and lowercase should not be considered unique) Closed: outdated ), so isn't a wholly bad thing.

Also I think leveraging Transliteration module will make this (and possibly other) functionality more locale-tolerant, so I don't think it's a problematic (possibly optional) dependency for this feature.

Hope to get a working patch posted shortly. If anybody wants to chip in sooner, let me know and I'll set up a public git repo. I need this feature for a D6 site, but happy to provide a D7 patch if the maintainer agrees to commit.