One of the indexers we support is whoosh. It has a few features that we aren't using.

One of which is a search language that supports:

  * AND and OR operations (along with ANDNOT, ANDMAYBE, and NOT )
  * "phrase searching"
  * NEAR operations
  * explicit fuzzy~ search (maybe replace current automatic fuzzy 1 change search)
  * (grouping and wildcards*) and more ...

https://whoosh.readthedocs.io/en/latest/parsing.html
https://whoosh.readthedocs.io/en/latest/querylang.html

We need:

  1) code to support extended queries rather than the simple word1 word2 with implied
     AND we currently use. Consider supporting a subset of the full query language
     and query parser. Something maybe googlish? Full support may be too confusing
     by default.

  2) admin options to enable extended queries - might be simple on/off/fuzzy or
     have a more extensive list that turns on sets of options.

  3) can the roundup admin override our simple option choices by using interfaces.py
     to permit more extensive customization?

  4) documentation for the changes - for admin and user