search for: fts_header_want_index

Hi all I discovered that the full-text search (fts) plugin can work without SQUAT/LUCENE/SOLR backend. I.e., Dovecot creates separate indexes for header search in files dovecot.index and dovecot.index.cache. Even, the search by headers is fast enough, and can search for phrases. Also, it seems that this buillt-in search is faster than Solr-based search. But if I enable the Solr backend (fts_solr),