13. An electronic system of accessing data in a record-based data storage system using a search engine in response to a join query, the electronic system comprising: a search engine configured to provide indices and return result sets from the indices in response to queries; storage to store the indices and result sets; a join engine configured to: query the search engine to provide join mappings to storage, the join mappings mapping join keys to documents and join key values to the documents; query the search engine to return primary and secondary result sets for primary and secondary queries of the join query; using the join mappings and result sets, identifying documents from the primary result sets and the secondary result sets that have common field values.
14. The system of claim 13 wherein the search engine is further configured to retrieve at least a subset of the identified documents from the primary result sets and the secondary result sets that have common field values.