Dandandan commented on code in PR #23032:
URL: https://github.com/apache/datafusion/pull/23032#discussion_r3448662205
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datafusion/physical-plan/src/joins/utils.rs:
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@@ -1373,13 +1373,218 @@ pub(crate) fn build_batch_from_indices(
Ok(RecordBatch::try_new(Arc::new(schema.clone()), columns)?)
}
+/// Computes prefix-sum offsets for a sequence of build-side batches.
+///
+/// `offsets[k]` is the flat row index at which batch `k` begins in the logical
+/// concatenation of all batches, and `offsets[n]` is the total row count. This
+/// lets a flat build-side index be mapped back to a `(batch, row)` pair
without
+/// materializing the concatenation.
+pub(crate) fn build_batch_offsets(
+ batch_row_counts: impl Iterator<Item = usize>,
+) -> Vec<usize> {
+ let mut offsets = vec![0usize];
+ let mut acc = 0usize;
+ for n in batch_row_counts {
Review Comment:
This could use `collect` here without zero-initializing
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