dbx_core/sql/executor/
hash_utils.rs

1//! Hashing utilities for Arrow batches — Provides vectorized hashing without per-row allocations.
2
3use crate::error::DbxResult;
4use ahash::RandomState;
5use arrow::array::*;
6use arrow::datatypes::DataType;
7use arrow::record_batch::RecordBatch;
8
9/// 배치의 지정된 컬럼들에 대해 행 단위 해시값을 계산하여 UInt64Array로 반환합니다.
10/// Vec<u8> 할당 없이 필드 값을 직접 해싱하여 속도를 극대화합니다.
11pub fn hash_batch(batch: &RecordBatch, columns: &[usize], seed: u64) -> DbxResult<UInt64Array> {
12    let num_rows = batch.num_rows();
13    if num_rows == 0 {
14        return Ok(UInt64Array::from(Vec::<u64>::new()));
15    }
16
17    let hasher_state = RandomState::with_seeds(seed, seed, seed, seed);
18    let mut hashes = vec![seed; num_rows];
19
20    for &col_idx in columns {
21        let col = batch.column(col_idx);
22        update_hashes(col, &mut hashes, &hasher_state)?;
23    }
24
25    Ok(UInt64Array::from(hashes))
26}
27
28/// 기존 해시값 배열에 새로운 컬럼의 해시값을 누적합니다.
29fn update_hashes(col: &ArrayRef, hashes: &mut [u64], hasher: &RandomState) -> DbxResult<()> {
30    let num_rows = col.len();
31
32    match col.data_type() {
33        DataType::Int32 => {
34            let arr = col.as_any().downcast_ref::<Int32Array>().unwrap();
35            for (i, hash) in hashes.iter_mut().enumerate().take(num_rows) {
36                if !arr.is_null(i) {
37                    let val_hash = hasher.hash_one(arr.value(i));
38                    *hash = combine_hashes(*hash, val_hash);
39                } else {
40                    *hash = combine_hashes(*hash, 0);
41                }
42            }
43        }
44        DataType::Int64 => {
45            let arr = col.as_any().downcast_ref::<Int64Array>().unwrap();
46            for (i, hash) in hashes.iter_mut().enumerate().take(num_rows) {
47                if !arr.is_null(i) {
48                    let val_hash = hasher.hash_one(arr.value(i));
49                    *hash = combine_hashes(*hash, val_hash);
50                } else {
51                    *hash = combine_hashes(*hash, 0);
52                }
53            }
54        }
55        DataType::Float64 => {
56            let arr = col.as_any().downcast_ref::<Float64Array>().unwrap();
57            for (i, hash) in hashes.iter_mut().enumerate().take(num_rows) {
58                if !arr.is_null(i) {
59                    let val_hash = hasher.hash_one(arr.value(i).to_bits());
60                    *hash = combine_hashes(*hash, val_hash);
61                } else {
62                    *hash = combine_hashes(*hash, 0);
63                }
64            }
65        }
66        DataType::Utf8 => {
67            let arr = col.as_any().downcast_ref::<StringArray>().unwrap();
68            for (i, hash) in hashes.iter_mut().enumerate().take(num_rows) {
69                if !arr.is_null(i) {
70                    let val_hash = hasher.hash_one(arr.value(i));
71                    *hash = combine_hashes(*hash, val_hash);
72                } else {
73                    *hash = combine_hashes(*hash, 0);
74                }
75            }
76        }
77        _ => {
78            // 다른 타입들은 포맷팅하여 해싱 (성능 저하 지점, 필요 시 확장)
79            for hash in hashes.iter_mut().take(num_rows) {
80                let val_hash = hasher.hash_one(format!("{:?}", col.as_any()));
81                *hash = combine_hashes(*hash, val_hash);
82            }
83        }
84    }
85    Ok(())
86}
87
88/// 두 해시값을 결합합니다 (Boost hash_combine 스타일).
89#[inline]
90fn combine_hashes(h1: u64, h2: u64) -> u64 {
91    // 0x9e3779b97f4a7c15는 골든 레이티오의 u64 버전
92    h1 ^ (h2
93        .wrapping_add(0x9e3779b97f4a7c15)
94        .wrapping_add(h1 << 6)
95        .wrapping_add(h1 >> 2))
96}
dbx_core/sql/executor/hash_utils.rs

dbx_core/sql/executor/
hash_utils.rs
