How do solr implement filter search

Can anyone point me to the piece of solr source c开发者_运维技巧ode which performs filter query (excecuting the fq=).

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Solr's main façade to Lucene is SolrIndexSearcher. In particular the getDocListC function seems to do the actual passing to Lucene.

Filter queries and other parameters are passed via a QueryCommand class, you can see that filter queries is simply a list of org.apache.lucene.search.Query, just like the "main query".