Mongodb match accented characters as underlying character

As of Mongo 3.2, you can use $text and set $diacriticSensitive to false:

{
  $text:
    {
      $search: <string>,
      $language: <string>,
      $caseSensitive: <boolean>,
      $diacriticSensitive: <boolean>
    }
}

See more in the Mongo docs: https://docs.mongodb.com/manual/reference/operator/query/text/

I suggest you add an indexed field like NameSearchable of simplified strings, e.g.

• João -> JOAO
• François -> FRANCOIS
• Jesús -> JESUS
• Jürgen -> JUERGEN

The same mapping that is used when inserting new items in the database can be used when searching. The original string with correct casing and accents will be preserved.

Most importantly, the query can make use of indexing. Case insensitive queries and regex queries can not use indexes (with the exception of rooted regexs) and will grow prohibitively slow on large collections.

Oh, and since the simplified strings can be created from the original strings, it's not a problem to add this to existing collections.

In this blog: http://tech.rgou.net/en/php/pesquisas-nao-sensiveis-ao-caso-e-acento-no-mongodb-e-php/

Somebody used the approach you were trying to do. This is as far as I know the only solution for the latest MongoDB version.