Disclosed herein are system, method, and computer program product embodiments for incrementally building hash collision tables. In some embodiments, hashes and hash collision tables may be used to improve efficiency of relational operations, such as those used in relational databases. An embodiment operates by determining hash collisions between data entries, then storing newly determined hash values corresponding to collisions in a hash collision table. The storing can be done incrementally, without needing to rebuild hash tables or hash collision tables for all data entries.