UBarney commented on code in PR #19602:
URL: https://github.com/apache/datafusion/pull/19602#discussion_r2659556702
##########
datafusion/physical-plan/src/joins/hash_join/partitioned_hash_eval.rs:
##########
@@ -327,12 +329,24 @@ impl PhysicalExpr for HashTableLookupExpr {
Ok(false)
}
- fn evaluate(
- &self,
- batch: &arrow::record_batch::RecordBatch,
- ) -> Result<ColumnarValue> {
+ fn evaluate(&self, batch: &RecordBatch) -> Result<ColumnarValue> {
let num_rows = batch.num_rows();
+ // Optimization: if hash_expr is HashExpr, compute hashes directly
into callback
+ // to avoid redundant allocations and copies.
+ if let Some(hash_expr) =
self.hash_expr.as_any().downcast_ref::<HashExpr>() {
Review Comment:
That's a great point. Storing the inner expressions directly is indeed a
better approach, especially since the perfect hash join(which is being worked
on [in that separate pending
PR](https://github.com/apache/datafusion/pull/19411/changes#diff-c89cc13760a9e27ff7901446ad0982fab905ae292b57803b53f749603168c7b6R361-R362))
needs direct access to `on_columns` to identify the join key columns.
I initially considered changing `HashTableLookupExpr.hash_expr` to a
concrete `HashExpr` type (which I've actually already done in another [unmerged
PR for perfect hash
join](https://github.com/apache/datafusion/pull/19411/changes#diff-c89cc13760a9e27ff7901446ad0982fab905ae292b57803b53f749603168c7b6R222)).
However, I think that accessing the columns through `hash_expr.on_columns`
feels a bit clunky 😂.
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