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Merged
Jefffrey merged 6 commits into from
Jan 19, 2026
Merged

perf: Optimize round scalar performance #19831

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9b6882f
perf: Optimize round scalar performance
kumarUjjawal Jan 15, 2026
c10b651
use round_float for consistency
kumarUjjawal Jan 16, 2026
3cb991e
add decimal support
kumarUjjawal Jan 16, 2026
3a77281
add unit test and refactor
kumarUjjawal Jan 17, 2026
1b99bb2
fix clippy issues
kumarUjjawal Jan 17, 2026
c66bb84
remove unit tests for the slt
kumarUjjawal Jan 17, 2026
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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 @@ -320,3 +320,8 @@ required-features = ["math_expressions"]
harness = false
name = "floor_ceil"
required-features = ["math_expressions"]

[[bench]]
harness = false
name = "round"
required-features = ["math_expressions"]
154 changes: 154 additions & 0 deletions datafusion/functions/benches/round.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,154 @@
// 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::datatypes::{DataType, Field, Float32Type, Float64Type};
use arrow::util::bench_util::create_primitive_array;
use criterion::{Criterion, SamplingMode, criterion_group, criterion_main};
use datafusion_common::ScalarValue;
use datafusion_common::config::ConfigOptions;
use datafusion_expr::{ColumnarValue, ScalarFunctionArgs};
use datafusion_functions::math::round;
use std::hint::black_box;
use std::sync::Arc;
use std::time::Duration;

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

for size in [1024, 4096, 8192] {
let mut group = c.benchmark_group(format!("round size={size}"));
group.sampling_mode(SamplingMode::Flat);
group.sample_size(10);
group.measurement_time(Duration::from_secs(10));

// Float64 array benchmark
let f64_array = Arc::new(create_primitive_array::<Float64Type>(size, 0.1));
let batch_len = f64_array.len();
let f64_args = vec![
ColumnarValue::Array(f64_array),
ColumnarValue::Scalar(ScalarValue::Int32(Some(2))),
];

group.bench_function("round_f64_array", |b| {
b.iter(|| {
let args_cloned = f64_args.clone();
black_box(
round_fn
.invoke_with_args(ScalarFunctionArgs {
args: args_cloned,
arg_fields: vec![
Field::new("a", DataType::Float64, true).into(),
Field::new("b", DataType::Int32, false).into(),
],
number_rows: batch_len,
return_field: Field::new("f", DataType::Float64, true).into(),
config_options: Arc::clone(&config_options),
})
.unwrap(),
)
})
});

// Float32 array benchmark
let f32_array = Arc::new(create_primitive_array::<Float32Type>(size, 0.1));
let f32_args = vec![
ColumnarValue::Array(f32_array),
ColumnarValue::Scalar(ScalarValue::Int32(Some(2))),
];

group.bench_function("round_f32_array", |b| {
b.iter(|| {
let args_cloned = f32_args.clone();
black_box(
round_fn
.invoke_with_args(ScalarFunctionArgs {
args: args_cloned,
arg_fields: vec![
Field::new("a", DataType::Float32, true).into(),
Field::new("b", DataType::Int32, false).into(),
],
number_rows: batch_len,
return_field: Field::new("f", DataType::Float32, true).into(),
config_options: Arc::clone(&config_options),
})
.unwrap(),
)
})
});

// Scalar benchmark (the optimization we added)
let scalar_f64_args = vec![
ColumnarValue::Scalar(ScalarValue::Float64(Some(std::f64::consts::PI))),
ColumnarValue::Scalar(ScalarValue::Int32(Some(2))),
];

group.bench_function("round_f64_scalar", |b| {
b.iter(|| {
let args_cloned = scalar_f64_args.clone();
black_box(
round_fn
.invoke_with_args(ScalarFunctionArgs {
args: args_cloned,
arg_fields: vec![
Field::new("a", DataType::Float64, false).into(),
Field::new("b", DataType::Int32, false).into(),
],
number_rows: 1,
return_field: Field::new("f", DataType::Float64, false)
.into(),
config_options: Arc::clone(&config_options),
})
.unwrap(),
)
})
});

let scalar_f32_args = vec![
ColumnarValue::Scalar(ScalarValue::Float32(Some(std::f32::consts::PI))),
ColumnarValue::Scalar(ScalarValue::Int32(Some(2))),
];

group.bench_function("round_f32_scalar", |b| {
b.iter(|| {
let args_cloned = scalar_f32_args.clone();
black_box(
round_fn
.invoke_with_args(ScalarFunctionArgs {
args: args_cloned,
arg_fields: vec![
Field::new("a", DataType::Float32, false).into(),
Field::new("b", DataType::Int32, false).into(),
],
number_rows: 1,
return_field: Field::new("f", DataType::Float32, false)
.into(),
config_options: Arc::clone(&config_options),
})
.unwrap(),
)
})
});

group.finish();
}
}

criterion_group!(benches, criterion_benchmark);
criterion_main!(benches);
131 changes: 130 additions & 1 deletion datafusion/functions/src/math/round.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,7 @@ use arrow::error::ArrowError;
use datafusion_common::types::{
NativeType, logical_float32, logical_float64, logical_int32,
};
use datafusion_common::{Result, ScalarValue, exec_err};
use datafusion_common::{DataFusionError, Result, ScalarValue, exec_err};
use datafusion_expr::sort_properties::{ExprProperties, SortProperties};
use datafusion_expr::{
Coercion, ColumnarValue, Documentation, ScalarFunctionArgs, ScalarUDFImpl, Signature,
Expand Down Expand Up @@ -141,6 +141,135 @@ impl ScalarUDFImpl for RoundFunc {
&default_decimal_places
};

// Scalar fast path for float and decimal types - avoid array conversion overhead
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@Jefffrey Jefffrey Jan 16, 2026

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        if let (ColumnarValue::Scalar(value_scalar), ColumnarValue::Scalar(dp_scalar)) =
            (&args.args[0], decimal_places)
        {
            if value_scalar.is_null() || dp_scalar.is_null() {
                return ColumnarValue::Scalar(ScalarValue::Null)
                    .cast_to(args.return_type(), None);
            }

            let dp = if let ScalarValue::Int32(Some(dp)) = dp_scalar {
                *dp
            } else {
                return internal_err!(
                    "Unexpected datatype for decimal_places: {}",
                    dp_scalar.data_type()
                );
            };

            match value_scalar {
                ScalarValue::Float32(Some(v)) => {
                    let rounded = round_float(*v, dp)?;
                    Ok(ColumnarValue::Scalar(ScalarValue::from(rounded)))
                }
                ScalarValue::Float64(Some(v)) => {
                    let rounded = round_float(*v, dp)?;
                    Ok(ColumnarValue::Scalar(ScalarValue::from(rounded)))
                }
                ScalarValue::Decimal128(Some(v), precision, scale) => {
                    let rounded = round_decimal(*v, *scale, dp)?;
                    let scalar =
                        ScalarValue::Decimal128(Some(rounded), *precision, *scale);
                    Ok(ColumnarValue::Scalar(scalar))
                }
                ScalarValue::Decimal256(Some(v), precision, scale) => {
                    let rounded = round_decimal(*v, *scale, dp)?;
                    let scalar =
                        ScalarValue::Decimal256(Some(rounded), *precision, *scale);
                    Ok(ColumnarValue::Scalar(scalar))
                }
                ScalarValue::Decimal64(Some(v), precision, scale) => {
                    let rounded = round_decimal(*v, *scale, dp)?;
                    let scalar =
                        ScalarValue::Decimal64(Some(rounded), *precision, *scale);
                    Ok(ColumnarValue::Scalar(scalar))
                }
                ScalarValue::Decimal32(Some(v), precision, scale) => {
                    let rounded = round_decimal(*v, *scale, dp)?;
                    let scalar =
                        ScalarValue::Decimal32(Some(rounded), *precision, *scale);
                    Ok(ColumnarValue::Scalar(scalar))
                }
                _ => {
                    internal_err!(
                        "Unexpected datatype for value: {}",
                        value_scalar.data_type()
                    )
                }
            }
        } else {
            round_columnar(&args.args[0], decimal_places, args.number_rows)
        }

Cleaner way of doing this

  • Using internal_err which are more appropriate here than exec_err
  • Collapse null handling using ScalarValue::is_null and ColumnarValue::cast_to
  • Don't need to map the error of round_float and round_decimal because using ? does that for us

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@kumarUjjawal kumarUjjawal Jan 17, 2026

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Thanks, this look much better.

if let (ColumnarValue::Scalar(value_scalar), ColumnarValue::Scalar(dp_scalar)) =
(&args.args[0], decimal_places)
{
// Extract decimal places as i32
// Note: decimal_places is coerced to Int32 by the signature, so the non-Int32
// arm should be unreachable in normal execution.
let dp = match dp_scalar {
ScalarValue::Int32(Some(dp)) => *dp,
ScalarValue::Int32(None) => {
// Return null with correct type for null decimal_places
return match value_scalar {
ScalarValue::Float32(_) => {
Ok(ColumnarValue::Scalar(ScalarValue::Float32(None)))
}
ScalarValue::Decimal128(_, p, s) => Ok(ColumnarValue::Scalar(
ScalarValue::Decimal128(None, *p, *s),
)),
ScalarValue::Decimal256(_, p, s) => Ok(ColumnarValue::Scalar(
ScalarValue::Decimal256(None, *p, *s),
)),
ScalarValue::Decimal64(_, p, s) => Ok(ColumnarValue::Scalar(
ScalarValue::Decimal64(None, *p, *s),
)),
ScalarValue::Decimal32(_, p, s) => Ok(ColumnarValue::Scalar(
ScalarValue::Decimal32(None, *p, *s),
)),
_ => Ok(ColumnarValue::Scalar(ScalarValue::Float64(None))),
};
}
_ => {
return exec_err!(
"Internal error: round decimal_places should be Int32, got {:?}",
dp_scalar
);
}
};

match value_scalar {
ScalarValue::Float64(Some(v)) => {
return round_float(*v, dp)
.map(|r| ColumnarValue::Scalar(ScalarValue::Float64(Some(r))))
.map_err(DataFusionError::from);
}
ScalarValue::Float64(None) => {
return Ok(ColumnarValue::Scalar(ScalarValue::Float64(None)));
}
ScalarValue::Float32(Some(v)) => {
return round_float(*v, dp)
.map(|r| ColumnarValue::Scalar(ScalarValue::Float32(Some(r))))
.map_err(DataFusionError::from);
}
ScalarValue::Float32(None) => {
return Ok(ColumnarValue::Scalar(ScalarValue::Float32(None)));
}
ScalarValue::Decimal128(Some(v), precision, scale) => {
return round_decimal(*v, *scale, dp)
.map(|r| {
ColumnarValue::Scalar(ScalarValue::Decimal128(
Some(r),
*precision,
*scale,
))
})
.map_err(DataFusionError::from);
}
ScalarValue::Decimal128(None, precision, scale) => {
return Ok(ColumnarValue::Scalar(ScalarValue::Decimal128(
None, *precision, *scale,
)));
}
ScalarValue::Decimal256(Some(v), precision, scale) => {
return round_decimal(*v, *scale, dp)
.map(|r| {
ColumnarValue::Scalar(ScalarValue::Decimal256(
Some(r),
*precision,
*scale,
))
})
.map_err(DataFusionError::from);
}
ScalarValue::Decimal256(None, precision, scale) => {
return Ok(ColumnarValue::Scalar(ScalarValue::Decimal256(
None, *precision, *scale,
)));
}
ScalarValue::Decimal64(Some(v), precision, scale) => {
return round_decimal(*v, *scale, dp)
.map(|r| {
ColumnarValue::Scalar(ScalarValue::Decimal64(
Some(r),
*precision,
*scale,
))
})
.map_err(DataFusionError::from);
}
ScalarValue::Decimal64(None, precision, scale) => {
return Ok(ColumnarValue::Scalar(ScalarValue::Decimal64(
None, *precision, *scale,
)));
}
ScalarValue::Decimal32(Some(v), precision, scale) => {
return round_decimal(*v, *scale, dp)
.map(|r| {
ColumnarValue::Scalar(ScalarValue::Decimal32(
Some(r),
*precision,
*scale,
))
})
.map_err(DataFusionError::from);
}
ScalarValue::Decimal32(None, precision, scale) => {
return Ok(ColumnarValue::Scalar(ScalarValue::Decimal32(
None, *precision, *scale,
)));
}
// All supported scalar types are handled above
_ => {
return exec_err!(
"Internal error: unexpected scalar type for round: {:?}",
value_scalar
);
}
}
}

round_columnar(&args.args[0], decimal_places, args.number_rows)
}

Expand Down