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Improve regexp kernels performance by avoiding cloning Regex #5235

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Dec 23, 2023
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10 changes: 4 additions & 6 deletions arrow-string/src/regexp.rs
Original file line number Diff line number Diff line change
Expand Up @@ -81,15 +81,14 @@ pub fn regexp_is_match_utf8<OffsetSize: OffsetSizeTrait>(
(Some(value), Some(pattern)) => {
let existing_pattern = patterns.get(&pattern);
let re = match existing_pattern {
Some(re) => re.clone(),
Some(re) => re,
None => {
let re = Regex::new(pattern.as_str()).map_err(|e| {
ArrowError::ComputeError(format!(
"Regular expression did not compile: {e:?}"
))
})?;
patterns.insert(pattern, re.clone());
re
patterns.entry(pattern).or_insert(re)
}
};
result.append(re.is_match(value));
Expand Down Expand Up @@ -216,15 +215,14 @@ pub fn regexp_match<OffsetSize: OffsetSizeTrait>(
(Some(value), Some(pattern)) => {
let existing_pattern = patterns.get(&pattern);
let re = match existing_pattern {
Some(re) => re.clone(),
Some(re) => re,
None => {
let re = Regex::new(pattern.as_str()).map_err(|e| {
ArrowError::ComputeError(format!(
"Regular expression did not compile: {e:?}"
))
})?;
patterns.insert(pattern, re.clone());
re
patterns.entry(pattern).or_insert(re)
Comment on lines 216 to +225
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If you replaced the get above with this entry call, it might improve the performance further by eliminating a branch perhaps??

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@viirya viirya Dec 22, 2023

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Hmm, then we need to use or_insert_with like

let re = patterns.entry(pattern).or_insert_with(|| {
  Regex::new(pattern.as_str()).map_err(|e| {
    ArrowError::ComputeError(format!(
      "Regular expression did not compile: {e:?}"
    ))
  }?)
});

But or_insert_with cannot propagate the error out of the function.

Tried with Result<Regex, ArrowError> as value type with the patterns HashMap, but then it doesn't work because the ? operator cannot be applied to type &mut Result<regex::Regex, arrow_schema::ArrowError> too.

So just keep it as is.

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@tustvold tustvold Dec 22, 2023

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Entry is an enumeration you can match on, you don't have to use or_insert_with and friends, they're just utilities like on Option

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Oh, the branch to eliminate is the one inside or_insert? Do you mean something like:

let entry = patterns.entry(pattern.clone());
let re = match entry {
  Entry::Occupied(entry) => entry.into_mut(),
  Entry::Vacant(entry) => {
    let re = Regex::new(pattern.as_str()).map_err(|e| {
      ArrowError::ComputeError(format!(
        "Regular expression did not compile: {e:?}"
      ))
    })?;
    entry.insert(re)
  }
};

Hmm, it actually gets regression a little. 🤔

regexp                  time:   [7.6891 ms 7.7210 ms 7.7511 ms]
                        change: [+14.792% +15.570% +16.321%] (p = 0.00 < 0.05)
                        Performance has regressed.

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That is what I meant, perhaps the regression is because of the added clone (which i think can be removed)

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clone? You mean let entry = patterns.entry(pattern.clone());? It cannot be removed.

216 |                 (Some(value), Some(pattern)) => {
    |                                    ------- move occurs because `pattern` has type `String`, which does not implement the `Copy` trait
217 |                     let entry = patterns.entry(pattern);
    |                                                ------- value moved here
...
221 |                             let re = Regex::new(pattern.as_str()).map_err(|e| {
    |                                                 ^^^^^^^ value borrowed here after move
    |
help: consider cloning the value if the performance cost is acceptable
    |
217 |                     let entry = patterns.entry(pattern.clone());
    |                                                       ++++++++

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Oh because of the unfortunate way flags are handled... Yeah this kernel would probably do with redesigning 😅

}
};
match re.captures(value) {
Expand Down
5 changes: 5 additions & 0 deletions arrow/Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -247,6 +247,11 @@ name = "substring_kernels"
harness = false
required-features = ["test_utils"]

[[bench]]
name = "regexp_kernels"
harness = false
required-features = ["test_utils"]

[[bench]]
name = "array_data_validate"
harness = false
Expand Down
44 changes: 44 additions & 0 deletions arrow/benches/regexp_kernels.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,44 @@
// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.

#[macro_use]
extern crate criterion;
use criterion::Criterion;

extern crate arrow;

use arrow::array::*;
use arrow::compute::kernels::regexp::*;
use arrow::util::bench_util::*;

fn bench_regexp(arr: &GenericStringArray<i32>, regex_array: &GenericStringArray<i32>) {
regexp_match(criterion::black_box(arr), regex_array, None).unwrap();
}

fn add_benchmark(c: &mut Criterion) {
let size = 65536;
let val_len = 1000;

let arr_string = create_string_array_with_len::<i32>(size, 0.0, val_len);
let pattern_values = vec![r".*-(\d*)-.*"; size];
let pattern = GenericStringArray::<i32>::from(pattern_values);

c.bench_function("regexp", |b| b.iter(|| bench_regexp(&arr_string, &pattern)));
}

criterion_group!(benches, add_benchmark);
criterion_main!(benches);
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