Language detection at query time for long Solr queries

Try to avoid long queries (hundreds or thousands of terms) as Apache Solr is not optimized for them.

But if you have to execute long queries against a Solr app you should use language detection at query time if the query language is not known. This improves relevancy (by stemming, analyzing, etc.) and performance (by a smaller index and stop words / common terms query). Additionally, language detection is the basis for using common grams in order to improve the performance of phrase queries.

Here is how it works:

• Do language detection at indexing time and put the resulting Solr documents in language specific fields (e.g. text_de, text_en, ...).  
• Do also language detection at  query time in order to search in the corresponding language specific fields. Here is a Github Gist with an implementation that uses Googles language detection library that outperforms the Tika library.