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Optimize allocation rate for int64 array in hex function #16483

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Optimize allocation rate for int64 array in hex function #16483

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39 changes: 34 additions & 5 deletions datafusion/spark/src/function/math/hex.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ use std::sync::Arc;
use crate::function::error_utils::{
invalid_arg_count_exec_err, unsupported_data_type_exec_err,
};
use arrow::array::{Array, StringArray};
use arrow::array::{Array, GenericStringBuilder, StringArray};
use arrow::datatypes::DataType;
use arrow::{
array::{as_dictionary_array, as_largestring_array, as_string_array},
Expand All @@ -35,6 +35,10 @@ use datafusion_expr::Signature;
use datafusion_expr::{ColumnarValue, ScalarFunctionArgs, ScalarUDFImpl, Volatility};
use std::fmt::Write;

/// Max length of a hex-encoded uint64 value is 16 characters.
/// E.g., `i64::MAX` is `7FFFFFFFFFFFFFFF` which is 16 characters long.
const MAX_HEX_INT64_LEN: usize = 16;

/// <https://spark.apache.org/docs/latest/api/sql/index.html#hex>
#[derive(Debug)]
pub struct SparkHex {
Expand Down Expand Up @@ -196,11 +200,23 @@ pub fn compute_hex(
ColumnarValue::Array(array) => match array.data_type() {
DataType::Int64 => {
let array = as_int64_array(array)?;
let arr_len = array.len();
let arr_content_len = arr_len * MAX_HEX_INT64_LEN;

// Optimized using a builder to avoid intermediate allocations
// during iter().map(...).collect()
let mut builder =
GenericStringBuilder::<i32>::with_capacity(arr_len, arr_content_len);
for value in array {
match value {
None => builder.append_null(),
Some(v) => builder.append_value(hex_int64(v)),
};
}

let hexed_array: StringArray =
array.iter().map(|v| v.map(hex_int64)).collect();
let hexed = builder.finish();

Ok(ColumnarValue::Array(Arc::new(hexed_array)))
Ok(ColumnarValue::Array(Arc::new(hexed)))
}
DataType::Utf8 => {
let array = as_string_array(array);
Expand Down Expand Up @@ -333,13 +349,17 @@ mod test {
input_builder.append_value(2);
input_builder.append_null();
input_builder.append_value(3);
input_builder.append_value(i64::MAX);
input_builder.append_value(i64::MIN);
let input = input_builder.finish();

let mut string_builder = StringBuilder::new();
string_builder.append_value("1");
string_builder.append_value("2");
string_builder.append_null();
string_builder.append_value("3");
string_builder.append_value("7FFFFFFFFFFFFFFF");
string_builder.append_value("8000000000000000");
let expected = string_builder.finish();

let columnar_value = ColumnarValue::Array(Arc::new(input));
Expand Down Expand Up @@ -397,7 +417,14 @@ mod test {

#[test]
fn test_spark_hex_int64() {
let int_array = Int64Array::from(vec![Some(1), Some(2), None, Some(3)]);
let int_array = Int64Array::from(vec![
Some(1),
Some(2),
None,
Some(3),
Some(i64::MAX),
Some(i64::MIN),
]);
let columnar_value = ColumnarValue::Array(Arc::new(int_array));

let result = super::spark_hex(&[columnar_value]).unwrap();
Expand All @@ -412,6 +439,8 @@ mod test {
Some("2".to_string()),
None,
Some("3".to_string()),
Some("7FFFFFFFFFFFFFFF".to_string()),
Some("8000000000000000".to_string()),
]);

assert_eq!(string_array, &expected_array);
Expand Down
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