Clever String Processing Algorithms in ClickHouse

Student: Kutenin Danila

Educational Programme: Applied Mathematics and Information Science (Bachelor)

Final Grade: 10

Year of Graduation: 2019

String processing algorithms are everywhere - each second thousands of text queries do string search across petabytes of possibly compressed data. Though there are many classic ways to do asymptotically optimal search but research still continue now for real data. We present self-designed new algorithm multi-Volnitsky to search across haystack with multiple needles at once that was implemented in the database system ClickHouse. We also implemented multiple regex search with hyperscan library. We added new ways to do an approximate search to find typos and similarities between strings. We paid attention to SIMD approaches of UTF-8 encoded string processing. We will also talk about LZ4 codec probabilistic optimization and how it is used in ClickHouse.

Full text (added May 15, 2019)

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