viirya commented on code in PR #424:
URL: https://github.com/apache/datafusion-comet/pull/424#discussion_r1600503628
##########
core/src/execution/datafusion/spark_hash.rs:
##########
@@ -238,55 +241,67 @@ macro_rules! hash_array_decimal {
fn create_hashes_dictionary<K: ArrowDictionaryKeyType>(
array: &ArrayRef,
hashes_buffer: &mut [u32],
+ multi_col: bool,
) -> Result<()> {
let dict_array =
array.as_any().downcast_ref::<DictionaryArray<K>>().unwrap();
-
- // Hash each dictionary value once, and then use that computed
- // hash for each key value to avoid a potentially expensive
- // redundant hashing for large dictionary elements (e.g. strings)
- let dict_values = Arc::clone(dict_array.values());
- let mut dict_hashes = vec![0; dict_values.len()];
- create_hashes(&[dict_values], &mut dict_hashes)?;
-
- for (hash, key) in hashes_buffer.iter_mut().zip(dict_array.keys().iter()) {
- if let Some(key) = key {
- let idx = key.to_usize().ok_or_else(|| {
- DataFusionError::Internal(format!(
- "Can not convert key value {:?} to usize in dictionary of
type {:?}",
- key,
- dict_array.data_type()
- ))
- })?;
- *hash = dict_hashes[idx]
- } // no update for Null, consistent with other hashes
+ if multi_col {
+ // unpack the dictionary array as each row may have a different hash
input
+ let unpacked = take(dict_array.values().as_ref(), dict_array.keys(),
None)?;
+ create_hashes(&[unpacked], hashes_buffer)?;
+ } else {
Review Comment:
`multi_col` is true for columns after first column. Why we need to unpack
the dictionary array for them particularly?
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