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perf: Improve performance of CAST from string to int #3017

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Merged
andygrove merged 7 commits into from
Jan 6, 2026
Merged

perf: Improve performance of CAST from string to int #3017

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42a6d64
perf_string_to_int
coderfender Dec 31, 2025
768a017
perf_string_to_int
coderfender Dec 31, 2025
ca90587
perf_string_to_int
coderfender Jan 1, 2026
2b331f0
perf_string_to_int
coderfender Jan 1, 2026
5abce5f
improve_benchmark
coderfender Jan 4, 2026
94d0f32
improve_benchmark_remove_unwanted_branching
coderfender Jan 5, 2026
f1299eb
improve_benchmark_remove_unwanted_branching_per_eval_mode
coderfender Jan 6, 2026
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69 changes: 43 additions & 26 deletions native/spark-expr/src/conversion_funcs/cast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -389,13 +389,23 @@ macro_rules! cast_utf8_to_int {
($array:expr, $eval_mode:expr, $array_type:ty, $cast_method:ident) => {{
let len = $array.len();
let mut cast_array = PrimitiveArray::<$array_type>::builder(len);
for i in 0..len {
if $array.is_null(i) {
cast_array.append_null()
} else if let Some(cast_value) = $cast_method($array.value(i), $eval_mode)? {
cast_array.append_value(cast_value);
} else {
cast_array.append_null()
if $array.null_count() == 0 {
for i in 0..len {
if let Some(cast_value) = $cast_method($array.value(i), $eval_mode)? {
cast_array.append_value(cast_value);
} else {
cast_array.append_null()
}
}
} else {
for i in 0..len {
if $array.is_null(i) {
cast_array.append_null()
} else if let Some(cast_value) = $cast_method($array.value(i), $eval_mode)? {
cast_array.append_value(cast_value);
} else {
cast_array.append_null()
}
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@coderfender coderfender Jan 3, 2026

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made null check conditional to remove unwanted branching

}
}
let result: SparkResult<ArrayRef> = Ok(Arc::new(cast_array.finish()) as ArrayRef);
Expand Down Expand Up @@ -1965,33 +1975,41 @@ fn do_cast_string_to_int<
type_name: &str,
min_value: T,
) -> SparkResult<Option<T>> {
let trimmed_str = str.trim();
if trimmed_str.is_empty() {
let bytes = str.as_bytes();
let mut start = 0;
let mut end = bytes.len();

while start < end && bytes[start].is_ascii_whitespace() {
start += 1;
}
while end > start && bytes[end - 1].is_ascii_whitespace() {
end -= 1;
}
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@coderfender coderfender Jan 5, 2026

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not creating a new string through trim function and just looping through whitespaces

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@andygrove andygrove Jan 5, 2026

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I was actually wrong in an earlier review when I suggested stopping using trim. trim does just return a slice on a &str, not a new String.

It may be worth considering using trim_ascii instead.

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@andygrove andygrove Jan 6, 2026

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I will look at using trim_ascii in a separate PR along with some other minor changes.


if start == end {
return none_or_err(eval_mode, type_name, str);
}
let trimmed_str = &str[start..end];
let len = trimmed_str.len();
let trimmed_bytes = trimmed_str.as_bytes();
let mut result: T = T::zero();
let mut negative = false;
let mut idx = 0;
let first_char = trimmed_bytes[0];
let negative = first_char == b'-';
if negative || first_char == b'+' {
idx = 1;
if len == 1 {
return none_or_err(eval_mode, type_name, str);
}
}
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@coderfender coderfender Jan 3, 2026

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Same (removed unwanted If branching)


let radix = T::from(10);
let stop_value = min_value / radix;
let mut parse_sign_and_digits = true;

for (i, ch) in trimmed_str.char_indices() {
for &ch in &trimmed_bytes[idx..] {
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@coderfender coderfender Jan 3, 2026

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Cleaner and faster approach to access the chars directly

if parse_sign_and_digits {
if i == 0 {
negative = ch == '-';
let positive = ch == '+';
if negative || positive {
if i + 1 == len {
// input string is just "+" or "-"
return none_or_err(eval_mode, type_name, str);
}
// consume this char
continue;
}
}

if ch == '.' {
if ch == b'.' {
if eval_mode == EvalMode::Legacy {
// truncate decimal in legacy mode
parse_sign_and_digits = false;
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@andygrove andygrove Jan 5, 2026

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The eval_mode does not change for different rows. It would likely be more performant to have separate implementations for legacy vs other modes to avoid the conditional in the hot loop.

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@coderfender coderfender Jan 5, 2026

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Great suggestion . Let me go ahead and make separate paths for each eval mode to prevent hot loops and update this thread with benchmarks

Expand All @@ -2014,7 +2032,6 @@ fn do_cast_string_to_int<
if result < stop_value {
return none_or_err(eval_mode, type_name, str);
}

// Since the previous result is greater than or equal to stopValue(Integer.MIN_VALUE /
// radix), we can just use `result > 0` to check overflow. If result
// overflows, we should stop
Expand Down
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