Hi,
1. The index table engine might be a solution for you. The recent plugin version does support detecting and indexing words with special characters. It may not work, but it’s definitely worth a try.
2. The search performance in most cases is equivalent with the server performance. There are however tricks to make it more efficient: https://wpdreams.gitbooks.io/ajax-search-pro-documentation/content/performance_tuning.html
3. Make sure that the search in terms option is enabled. If you already have performance issue, I recommend solution #2 from this documentation (with index table engine): https://wpdreams.gitbooks.io/ajax-search-pro-documentation/content/general_settings/search_in_terms_categories,_tags.html
Best,Ernest Marcinko
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