Modern Minimal Perfect Hashing: A Survey

Given a set 𝑆 of 𝑛 keys, a perfect hash function for 𝑆 maps the keys in 𝑆 to the first 𝑚 ≥ 𝑛 integers without
collisions. It may return an arbitrary result for any key not in 𝑆 and is called minimal if 𝑚 = 𝑛. The most
important parameters are its space consumption, construction time, and query time. Years of research now
enable modern perfect hash functions to be extremely fast to query, very space-efficient, and scale to billions
of keys. Different approaches give different trade-offs between these aspects. For example, the smallest
constructions get within 0.1% of the space lower bound of log2
�
� bits per key. Others are particularly fast
to query, requiring only one memory access. Perfect hashing has many applications, for example, to avoid
collision resolution in static hash tables, and is used in databases, bioinformatics, and stringology.
Since the last comprehensive survey in 1997, significant progress has been made. This survey covers the
latest developments and provides a starting point for getting familiar with the topic. Additionally, our extensive
experimental evaluation can serve as a guide to select a perfect hash function for use in applications.