Zhuang Tianyi created ARROW-8681:
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Summary: Improve like/nlike performance
Key: ARROW-8681
URL: https://issues.apache.org/jira/browse/ARROW-8681
Project: Apache Arrow
Issue Type: Improvement
Components: Rust, Rust - DataFusion
Affects Versions: 0.17.0
Reporter: Zhuang Tianyi
Currently, the implementation of `like_utf8` and `nlike_utf8` is based on
regex, which is simple and readable, but poor at the performance.
I do some benchmark in [https://github.com/TennyZhuang/like-bench/] , in this
repo, I compare three like algorithm.
# `like`(includes partial_like): this is the first naive version, using the
recursive approach, which will cause terrible performance on special attack
input, such as `a%a%a%a%a%a%a%a%b`.
# `like_to_regex`: which is almost the same as the current implementation in
arrow.
# `like_optimize`: the like problem is similar to glob in shell, so a perfect
solution is proposed in [https://research.swtch.com/glob] . The code in the
research is written golang but I translate it to rust.
In my benchmark result, the recursive solution can be ignored due to bad time
complexity lower bound.
the regex solution will cost about 1000x time including regex compiling, and
about 4x time without regex compiling then solution 3. And It seems that the
code complexity is acceptable.
Everyone can reproduce the benchmark result using this repo with a few code.
I have submitted a PR to TiKV to optimize the like performance
([https://github.com/tikv/tikv/pull/5866/files|https://github.com/tikv/tikv/pull/5866/files)],
without UTF-8 support), and add collation support in
[https://github.com/tikv/tikv/pull/6592], which can be simply port to
data-fusion.
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