Django-haystack Whoosh backend with character folding

folding_whoosh_backend.py

# -*- coding: utf-8 -*-

"""
Whoosh backend for haystack that implements character folding, as per 
http://packages.python.org/Whoosh/stemming.html#character-folding .

Tested with Haystack 2.4.0 and Whooch 2.7.0

To use, put this file on your path and add it to your haystack settings, eg.

    HAYSTACK_CONNECTIONS = {
        'default': {
            'ENGINE': 'folding_whoosh_backend.FoldingWhooshEngine',
            'PATH': 'path-to-whoosh-index',
        },
    }
"""

from haystack.backends.whoosh_backend import WhooshEngine, WhooshSearchBackend
from whoosh.analysis import CharsetFilter, StemmingAnalyzer
from whoosh.support.charset import accent_map
from whoosh.fields import TEXT


class FoldingWhooshSearchBackend(WhooshSearchBackend):
    
    def build_schema(self, fields):
        schema = super(FoldingWhooshSearchBackend, self).build_schema(fields)
        
        for name, field in schema[1].items():
            if isinstance(field, TEXT):
                field.analyzer = StemmingAnalyzer() | CharsetFilter(accent_map)
                
        return schema


class FoldingWhooshEngine(WhooshEngine):
    backend = FoldingWhooshSearchBackend

I still cannot search using the words without accents like:
search with 'cafe' and get back results like: 'café', 'cafe'.
Do I have to do something additional like changing the index template?

@paweloque, no, you should just be able to change the backend. Make sure you reindex the content after doing this.

Great stuff, thanks @gregplaysguitar

if you use a EdgeNgramField, you can use this:

if isinstance(field, NGRAMWORDS):
    field.analyzer = StemmingAnalyzer() | NgramFilter(minsize=X) | CharsetFilter(accent_map)

or, event better maybe, keep the original analyzer, and add the filter like this;

field.analyzer = field.analyzer | CharsetFilter(accent_map)