A query is separated into subqueries including a first subquery containing terms applicable to a first data store and a second subquery containing terms applicable to a second data store, where both data stores maintain information regarding the documents. Applying the first subquery to the first data store retrieves a first list of document identifiers associated with documents that satisfy the terms of the first subquery. The first list is combined with the second subquery to form a masked subquery, which is applied to the second data store. The masked subquery only seeks to identify document identifiers that both are included the first list and that satisfy terms of the second query. The document identifiers included in the first list may be ordered to match an order in which the document identifiers are ordered in the second data store.