Dandandan commented on code in PR #16716:
URL: https://github.com/apache/datafusion/pull/16716#discussion_r2196037862
##########
datafusion/physical-plan/src/joins/utils.rs:
##########
@@ -928,6 +929,55 @@ pub(crate) fn build_batch_from_indices(
Ok(RecordBatch::try_new(Arc::new(schema.clone()), columns)?)
}
+/// Returns a new [RecordBatch] resulting of a join where the build/left side
is empty.
+/// The resulting batch has [Schema] `schema`.
+pub(crate) fn build_batch_empty_build_side(
+ schema: &Schema,
+ build_batch: &RecordBatch,
+ probe_batch: &RecordBatch,
+ column_indices: &[ColumnIndex],
+ join_type: JoinType,
+) -> Result<RecordBatch> {
+ match join_type {
+ // these join types only return data if the left side is not empty, so
we return an
+ // empty RecordBatch
+ JoinType::Inner
Review Comment:
I think it *should* be relatively fast to do a cross join / NLJ instead of a
hash join for those cases, but of course depends how the nested loop join is
implemented, probably there is more room for optimization of the nested loop
join.
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