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fix: Track metrics in hash joins with empty build sides #20810

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2010YOUY01 merged 2 commits into from
Mar 13, 2026
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fix: Track metrics in hash joins with empty build sides #20810

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b3f877d
fix: Track metrics in hash joins with empty build sides
nuno-faria Mar 8, 2026
17b1670
Update datafusion/sqllogictest/test_files/joins.slt
nuno-faria Mar 11, 2026
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4 changes: 2 additions & 2 deletions datafusion/physical-plan/src/joins/hash_join/stream.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -655,10 +655,10 @@ impl HashJoinStream {
self.join_type,
)?;
timer.done();
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@2010YOUY01 2010YOUY01 Mar 11, 2026

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Not related to this PR, but I noticed we don’t need to explicitly end the timer here since it’s an RAII variable. I’ll open a separate PR after this is merged.


self.output_buffer.push_batch(result)?;
self.state = HashJoinStreamState::FetchProbeBatch;

return Ok(StatefulStreamResult::Ready(Some(result)));
return Ok(StatefulStreamResult::Continue);
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@jonathanc-n jonathanc-n Mar 8, 2026 •
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I think we can slowly transition everything to slowly not need to variants of StatefulStreamResult, maybe an issue can be raised for this. It goes hand in hand with using the limited batch coalescer

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@jonathanc-n jonathanc-n Mar 8, 2026 •
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@Dandandan We can replicate the pattern you added with LimitedBatchCoalescer and updating metrics in poll_next_impl throughout the codebase

}

// get the matched by join keys indices
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43 changes: 43 additions & 0 deletions datafusion/sqllogictest/test_files/joins.slt
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Expand Up @@ -5056,6 +5056,49 @@ LEFT ANTI JOIN t2 ON k1 = k2
WHERE k1 < 0
----

# Also check that the reported number of output rows/batches are correct in the "empty build side"
# optimization.
# Issue: https://github.com/apache/datafusion/issues/20809
query TT
EXPLAIN ANALYZE
WITH t1 (k) AS (
VALUES (1), (2)
), t2 (k) AS (
VALUES (1)
)
SELECT *
FROM t1
LEFT ANTI JOIN (
SELECT *
FROM t2
WHERE k <> 1
) t2 ON t1.k = t2.k;
----
Plan with Metrics
01)HashJoinExec: mode=CollectLeft, join_type=RightAnti, on=[(k@0, k@0)], metrics=[output_rows=2, elapsed_compute=<slt:ignore>, output_bytes=<slt:ignore>, output_batches=1, array_map_created_count=0, build_input_batches=0, build_input_rows=0, input_batches=1, input_rows=2, build_mem_used=<slt:ignore>, build_time=<slt:ignore>, join_time=<slt:ignore>, avg_fanout=N/A (0/0), probe_hit_rate=0% (0/2)]
02)--ProjectionExec: expr=[column1@0 as k], metrics=[output_rows=0, elapsed_compute=<slt:ignore>, output_bytes=<slt:ignore>, output_batches=0, expr_0_eval_time=<slt:ignore>]
03)----FilterExec: column1@0 != 1, metrics=[output_rows=0, elapsed_compute=<slt:ignore>, output_bytes=<slt:ignore>, output_batches=0, selectivity=0% (0/1)]
04)------DataSourceExec: partitions=1, partition_sizes=[1], metrics=[]
05)--ProjectionExec: expr=[column1@0 as k], metrics=[output_rows=2, elapsed_compute=<slt:ignore>, output_bytes=<slt:ignore>, output_batches=1, expr_0_eval_time=<slt:ignore>]
06)----DataSourceExec: partitions=1, partition_sizes=[1], metrics=[]

query I
WITH t1 (k) AS (
VALUES (1), (2)
), t2 (k) AS (
VALUES (1)
)
SELECT *
FROM t1
LEFT ANTI JOIN (
SELECT *
FROM t2
WHERE k <> 1
) t2 ON t1.k = t2.k;
----
1
2

# Mark testing
statement ok
CREATE OR REPLACE TABLE t1(b INT, c INT, d INT);
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