Abstract: A method and apparatus for performing recursive database operations is provided. According to one aspect, a plurality of first-stage slaves and a plurality of second-stage slaves are established in a database server. During one or more iterations of a recursive database operation, the first-stage slaves concurrently process data items stored in a data repository and send results to the second-stage slaves. The second-stage slaves receive the results and concurrently process those results. The second-stage slaves store the results of the second-stage slaves' processing in the data repository. Subsequent iterations of the recursive database operation proceed in this manner until the recursive database operation has been completed. In each iteration, the first-stage slaves consume the product of the second-stage slaves' previous iteration's processing, and the second-stage slaves consume the product of the first-stage slaves' current iteration's processing.

Abstract: A search system generates an index for databases by generatively sampling the databases and uses that index to identify and formulate queries for searching the databases. The generated index is referred to as a domain-attribute index and contains a domain-level index and site-level indexes. A site-level index for a database maps site attributes to distinct attribute values within the database. The domain-level index for a domain maps attribute values to database and site attribute pairs that contain those attribute values. To generate a site-level index for a database within a certain domain, the search system starts out with an initial set of the sample data for that domain. The search system generates sampling queries based on the sample data and submits the sampling queries to a database. The search system updates the site-level index based on the sampling results and uses the results to generate more sampling queries.