Use of collation in mongodb $regex

Question

Since v3.4 collations are available for find operations, especially as matches for diacritic characters are concerned. While a find query with a definite value ($eq opeartor

Answer 1

There is no need to use collation on top of regex. You can functionally implement this behaviour using the correct regex.

Considering to the Antwerpen example the following regex gives you all the matches in the database:

/antw[eë]repen/i

To generate the above regex you have to regex-replace your search string first using the following replace formula:

str.replace(/e/ig, '[eë]')

And of course you have to do it with all diactric character. Also you can simply use the following library: diacritic-regex.

Answer 2

Documentation

Case insensitive regular expression queries generally cannot use indexes effectively. The $regex implementation is not collation-aware and is unable to utilize case-insensitive indexes.