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fix: Skip buffered rows which are not joined with streamed side when checking join filter results #12159

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Aug 26, 2024
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fix: Skip buffered rows which are not joined with streamed side when checking join filter results #12159

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6 changes: 6 additions & 0 deletions datafusion/physical-plan/src/joins/sort_merge_join.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1474,6 +1474,12 @@ impl SMJStream {
[chunk.buffered_batch_idx.unwrap()];

for i in 0..pre_mask.len() {
// If the buffered row is not joined with streamed side,
// skip it.
if buffered_indices.is_null(i) {
continue;
}

Comment on lines +1477 to +1482
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@viirya viirya Aug 25, 2024 •
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I was trying to duplicate the Spark SQL test but the test failure depends on the data distribution. I cannot make it as same as Spark case.

The test case looks like

select * from (
with left as (
    select N, L from (select unnest(make_array(1, 2, 3, 4)) N, unnest(make_array('A', 'B', 'C', 'D')) L) where N <= 4
), right as (
    select N, L from (select unnest(make_array(1, 2, 3, 4)) N, unnest(make_array('A', 'B', 'C', 'D')) L) where N >= 3
)
select * from left full join right on left.N = right.N and left.N != 3
) order by 1, 2, 3, 4;

I want those values to be in same partition to run sort merge join. So the joined batch looks like:

1 A null null
2 B null null # this and above row wrongly considered passing join filter for buffered row [3, C]
3 C 3 C   # join filter => false
4 D 4 D   # join filter => true

The buffered row [3, C] fails join filter. So it should be output as null joined buffered row, but the two above rows are wrongly considered passing join filter for buffered index 0 (i.e., [3, C]), it will not be output in Comet.

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The test case in Comet is apache/datafusion-comet#553 (comment)

let buffered_index = buffered_indices.value(i);

buffered_batch.join_filter_failed_map.insert(
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