This plugin extends Elasticsearch with new search actions and a filter query parser that enables to perform a "Filter Join" between two set of documents (in the same index or in different indexes).

The Filter Join is basically a (left) semi-join between two set of documents based on a common attribute, where the result only contains the attributes of one of the joined set of documents. This join is used to filter one document set based on a second document set, hence its name. It is equivalent to the EXISTS() operator in SQL.