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perf: Improve performance of split_part #19570

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386176a
optimize split_part
andygrove Dec 30, 2025
36ea121
optimize split_part
andygrove Dec 30, 2025
04fe9b4
cargo fmt
andygrove Dec 30, 2025
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5 changes: 5 additions & 0 deletions datafusion/functions/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -294,3 +294,8 @@ required-features = ["unicode_expressions"]
harness = false
name = "levenshtein"
required-features = ["unicode_expressions"]

[[bench]]
harness = false
name = "split_part"
required-features = ["string_expressions"]
382 changes: 382 additions & 0 deletions datafusion/functions/benches/split_part.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,382 @@
// 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.

extern crate criterion;

use arrow::array::{ArrayRef, Int64Array, StringArray, StringViewArray};
use arrow::datatypes::{DataType, Field};
use criterion::{BenchmarkId, Criterion, criterion_group, criterion_main};
use datafusion_common::config::ConfigOptions;
use datafusion_expr::{ColumnarValue, ScalarFunctionArgs};
use datafusion_functions::string::split_part;
use rand::distr::Alphanumeric;
use rand::prelude::StdRng;
use rand::{Rng, SeedableRng};
use std::hint::black_box;
use std::sync::Arc;

const N_ROWS: usize = 8192;

/// Generate test data for split_part benchmarks
/// Creates strings with multiple parts separated by the delimiter
fn gen_split_part_data(
n_rows: usize,
num_parts: usize, // number of parts in each string (separated by delimiter)
part_len: usize, // length of each part
delimiter: &str, // the delimiter to use
use_string_view: bool, // false -> StringArray, true -> StringViewArray
) -> (ColumnarValue, ColumnarValue) {
let mut rng = StdRng::seed_from_u64(42);

let mut strings: Vec<String> = Vec::with_capacity(n_rows);
for _ in 0..n_rows {
let mut parts: Vec<String> = Vec::with_capacity(num_parts);
for _ in 0..num_parts {
let part: String = (&mut rng)
.sample_iter(&Alphanumeric)
.take(part_len)
.map(char::from)
.collect();
parts.push(part);
}
strings.push(parts.join(delimiter));
}

let delimiters: Vec<String> = vec![delimiter.to_string(); n_rows];

if use_string_view {
let string_array: StringViewArray = strings.into_iter().map(Some).collect();
let delimiter_array: StringViewArray = delimiters.into_iter().map(Some).collect();
(
ColumnarValue::Array(Arc::new(string_array) as ArrayRef),
ColumnarValue::Array(Arc::new(delimiter_array) as ArrayRef),
)
} else {
let string_array: StringArray = strings.into_iter().map(Some).collect();
let delimiter_array: StringArray = delimiters.into_iter().map(Some).collect();
(
ColumnarValue::Array(Arc::new(string_array) as ArrayRef),
ColumnarValue::Array(Arc::new(delimiter_array) as ArrayRef),
)
}
}

fn gen_positions(n_rows: usize, position: i64) -> ColumnarValue {
let positions: Vec<i64> = vec![position; n_rows];
ColumnarValue::Array(Arc::new(Int64Array::from(positions)) as ArrayRef)
}

fn criterion_benchmark(c: &mut Criterion) {
let split_part_func = split_part();
let config_options = Arc::new(ConfigOptions::default());

let mut group = c.benchmark_group("split_part");

// Test different scenarios
// Scenario 1: Single-char delimiter, first position (should be fastest with optimization)
{
let (strings, delimiters) = gen_split_part_data(N_ROWS, 10, 8, ".", false);
let positions = gen_positions(N_ROWS, 1);
let args = vec![strings, delimiters, positions];
let arg_fields: Vec<_> = args
.iter()
.enumerate()
.map(|(idx, arg)| {
Field::new(format!("arg_{idx}"), arg.data_type(), true).into()
})
.collect();
let return_field = Field::new("f", DataType::Utf8, true).into();

group.bench_function(BenchmarkId::new("single_char_delim", "pos_first"), |b| {
b.iter(|| {
black_box(
split_part_func
.invoke_with_args(ScalarFunctionArgs {
args: args.clone(),
arg_fields: arg_fields.clone(),
number_rows: N_ROWS,
return_field: Arc::clone(&return_field),
config_options: Arc::clone(&config_options),
})
.expect("split_part should work"),
)
})
});
}

// Scenario 2: Single-char delimiter, middle position
{
let (strings, delimiters) = gen_split_part_data(N_ROWS, 10, 8, ".", false);
let positions = gen_positions(N_ROWS, 5);
let args = vec![strings, delimiters, positions];
let arg_fields: Vec<_> = args
.iter()
.enumerate()
.map(|(idx, arg)| {
Field::new(format!("arg_{idx}"), arg.data_type(), true).into()
})
.collect();
let return_field = Field::new("f", DataType::Utf8, true).into();

group.bench_function(BenchmarkId::new("single_char_delim", "pos_middle"), |b| {
b.iter(|| {
black_box(
split_part_func
.invoke_with_args(ScalarFunctionArgs {
args: args.clone(),
arg_fields: arg_fields.clone(),
number_rows: N_ROWS,
return_field: Arc::clone(&return_field),
config_options: Arc::clone(&config_options),
})
.expect("split_part should work"),
)
})
});
}

// Scenario 3: Single-char delimiter, last position
{
let (strings, delimiters) = gen_split_part_data(N_ROWS, 10, 8, ".", false);
let positions = gen_positions(N_ROWS, 10);
let args = vec![strings, delimiters, positions];
let arg_fields: Vec<_> = args
.iter()
.enumerate()
.map(|(idx, arg)| {
Field::new(format!("arg_{idx}"), arg.data_type(), true).into()
})
.collect();
let return_field = Field::new("f", DataType::Utf8, true).into();

group.bench_function(BenchmarkId::new("single_char_delim", "pos_last"), |b| {
b.iter(|| {
black_box(
split_part_func
.invoke_with_args(ScalarFunctionArgs {
args: args.clone(),
arg_fields: arg_fields.clone(),
number_rows: N_ROWS,
return_field: Arc::clone(&return_field),
config_options: Arc::clone(&config_options),
})
.expect("split_part should work"),
)
})
});
}

// Scenario 4: Single-char delimiter, negative position (last element)
{
let (strings, delimiters) = gen_split_part_data(N_ROWS, 10, 8, ".", false);
let positions = gen_positions(N_ROWS, -1);
let args = vec![strings, delimiters, positions];
let arg_fields: Vec<_> = args
.iter()
.enumerate()
.map(|(idx, arg)| {
Field::new(format!("arg_{idx}"), arg.data_type(), true).into()
})
.collect();
let return_field = Field::new("f", DataType::Utf8, true).into();

group.bench_function(
BenchmarkId::new("single_char_delim", "pos_negative"),
|b| {
b.iter(|| {
black_box(
split_part_func
.invoke_with_args(ScalarFunctionArgs {
args: args.clone(),
arg_fields: arg_fields.clone(),
number_rows: N_ROWS,
return_field: Arc::clone(&return_field),
config_options: Arc::clone(&config_options),
})
.expect("split_part should work"),
)
})
},
);
}

// Scenario 5: Multi-char delimiter, first position
{
let (strings, delimiters) = gen_split_part_data(N_ROWS, 10, 8, "~@~", false);
let positions = gen_positions(N_ROWS, 1);
let args = vec![strings, delimiters, positions];
let arg_fields: Vec<_> = args
.iter()
.enumerate()
.map(|(idx, arg)| {
Field::new(format!("arg_{idx}"), arg.data_type(), true).into()
})
.collect();
let return_field = Field::new("f", DataType::Utf8, true).into();

group.bench_function(BenchmarkId::new("multi_char_delim", "pos_first"), |b| {
b.iter(|| {
black_box(
split_part_func
.invoke_with_args(ScalarFunctionArgs {
args: args.clone(),
arg_fields: arg_fields.clone(),
number_rows: N_ROWS,
return_field: Arc::clone(&return_field),
config_options: Arc::clone(&config_options),
})
.expect("split_part should work"),
)
})
});
}

// Scenario 6: Multi-char delimiter, middle position
{
let (strings, delimiters) = gen_split_part_data(N_ROWS, 10, 8, "~@~", false);
let positions = gen_positions(N_ROWS, 5);
let args = vec![strings, delimiters, positions];
let arg_fields: Vec<_> = args
.iter()
.enumerate()
.map(|(idx, arg)| {
Field::new(format!("arg_{idx}"), arg.data_type(), true).into()
})
.collect();
let return_field = Field::new("f", DataType::Utf8, true).into();

group.bench_function(BenchmarkId::new("multi_char_delim", "pos_middle"), |b| {
b.iter(|| {
black_box(
split_part_func
.invoke_with_args(ScalarFunctionArgs {
args: args.clone(),
arg_fields: arg_fields.clone(),
number_rows: N_ROWS,
return_field: Arc::clone(&return_field),
config_options: Arc::clone(&config_options),
})
.expect("split_part should work"),
)
})
});
}

// Scenario 7: StringViewArray, single-char delimiter, first position
{
let (strings, delimiters) = gen_split_part_data(N_ROWS, 10, 8, ".", true);
let positions = gen_positions(N_ROWS, 1);
let args = vec![strings, delimiters, positions];
let arg_fields: Vec<_> = args
.iter()
.enumerate()
.map(|(idx, arg)| {
Field::new(format!("arg_{idx}"), arg.data_type(), true).into()
})
.collect();
let return_field = Field::new("f", DataType::Utf8, true).into();

group.bench_function(
BenchmarkId::new("string_view_single_char", "pos_first"),
|b| {
b.iter(|| {
black_box(
split_part_func
.invoke_with_args(ScalarFunctionArgs {
args: args.clone(),
arg_fields: arg_fields.clone(),
number_rows: N_ROWS,
return_field: Arc::clone(&return_field),
config_options: Arc::clone(&config_options),
})
.expect("split_part should work"),
)
})
},
);
}

// Scenario 8: Many parts (20), position near end - shows benefit of early termination
{
let (strings, delimiters) = gen_split_part_data(N_ROWS, 20, 8, ".", false);
let positions = gen_positions(N_ROWS, 2);
let args = vec![strings, delimiters, positions];
let arg_fields: Vec<_> = args
.iter()
.enumerate()
.map(|(idx, arg)| {
Field::new(format!("arg_{idx}"), arg.data_type(), true).into()
})
.collect();
let return_field = Field::new("f", DataType::Utf8, true).into();

group.bench_function(BenchmarkId::new("many_parts_20", "pos_second"), |b| {
b.iter(|| {
black_box(
split_part_func
.invoke_with_args(ScalarFunctionArgs {
args: args.clone(),
arg_fields: arg_fields.clone(),
number_rows: N_ROWS,
return_field: Arc::clone(&return_field),
config_options: Arc::clone(&config_options),
})
.expect("split_part should work"),
)
})
});
}

// Scenario 9: Long strings with many parts - worst case for old implementation
{
let (strings, delimiters) = gen_split_part_data(N_ROWS, 50, 16, "/", false);
let positions = gen_positions(N_ROWS, 1);
let args = vec![strings, delimiters, positions];
let arg_fields: Vec<_> = args
.iter()
.enumerate()
.map(|(idx, arg)| {
Field::new(format!("arg_{idx}"), arg.data_type(), true).into()
})
.collect();
let return_field = Field::new("f", DataType::Utf8, true).into();

group.bench_function(
BenchmarkId::new("long_strings_50_parts", "pos_first"),
|b| {
b.iter(|| {
black_box(
split_part_func
.invoke_with_args(ScalarFunctionArgs {
args: args.clone(),
arg_fields: arg_fields.clone(),
number_rows: N_ROWS,
return_field: Arc::clone(&return_field),
config_options: Arc::clone(&config_options),
})
.expect("split_part should work"),
)
})
},
);
}

group.finish();
}

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