lyne7-sc opened a new pull request, #25363:
URL: https://github.com/apache/datafusion/pull/25363
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## Rationale for this change
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Hash joins can spend substantial time looking up probe keys that do not
exist on the build side. For a single integer key with a bounded range, an
exact membership bitmap can reject these keys cheaply before hash table lookup.
This helps when many nonmatching keys reach the join, including when dynamic
filters cannot be pushed down to the input.
For example, in the measured TPC-H SF1 plans, the `RightSemi` join on
`part.p_partkey = lineitem.l_partkey` receives approximately 6 million probe
rows. With memtable inputs or the default Parquet configuration:
- **Q8:** Only **0.73%** of probe rows match the filtered build side,
resulting in approximately 5.96 million unsuccessful hash table lookups.
- **Q9:** Only **5.32%** of probe rows match the filtered build side,
resulting in approximately 5.68 million unsuccessful hash table lookups.
These low probe hit rates leave substantial room to avoid unsuccessful
lookups, reflected in both the query-latency and operator-level measurements
below.
The extra membership check is less useful when most keys match. An adaptive
policy pauses filtering when the observed pruning ratio is low and periodically
samples again as the input changes.
## What changes are included in this PR?
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- Build an optional integer membership bitmap for eligible single-key
HashMap joins in both CollectLeft and Partitioned modes. ArrayMap and
null-aware joins retain their existing paths.
- Generate a lookup mask for each probe batch, skipping hash table lookups
for absent keys. Preserve the original probe rows and NULL handling so outer,
anti, and mark join semantics remain unchanged. Hash computation is unchanged.
- Track pruning independently in each probe stream. Unproductive sampling
windows trigger progressively longer pauses; productive samples reset the pause
interval.
- Account for bitmap and mask memory through the memory pool, falling back
to normal lookup when an optional reservation cannot be satisfied.
- Add configuration, documentation, creation/pruning metrics, and the
`hash_join_probe` microbenchmark.
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- Unit tests cover membership and integer boundaries, range overflow, bitmap
boundaries, adaptive sampling/backoff, and sliced validity masks.
- HashJoin tests cover fallback paths, memory reservation failures, and
independent probe-stream adaptation with a shared build bitmap.
- `hash_join_integer_prefilter.slt` covers duplicate matches, unmatched
rows, NULL equality, inner/full/semi/anti joins, null-aware IN/NOT IN behavior,
range limits, and creation/pruning metrics.
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The feature is opt-in and disabled by default. It can be enabled with:
```sql
SET datafusion.execution.enable_join_integer_prefilter = true;
```
Additional execution options control the maximum key range (default
`262144`), minimum pruning ratio (`0.5`), and sampling window (`12288` input
rows). The metrics `integer_prefilter_created_count` and
`probe_prefilter_rows_pruned` expose whether the prefilter was created and how
many probe rows skipped lookup.
Query results are unchanged.
## Benchmarks
### Microbench: `hash_join_probe`
| Workload | Main | Off | On | On vs main |
|---|---:|---:|---:|---:|
| RightSemi, 10% interleaved hits | 5.335 | 5.293 | 3.985 | -25.3% |
| RightAnti, 10% interleaved hits | 10.849 | 10.933 | 9.479 | -12.6% |
| Inner, 10% interleaved hits | 6.114 | 6.164 | 4.802 | -21.4% |
| RightSemi, 10% clustered hits | 4.286 | 4.338 | 3.549 | -17.2% |
| RightAnti, 10% clustered hits | 10.172 | 11.633 | 8.969 | -11.8% |
| RightSemi, all hits | 13.066 | 12.897 | 13.061 | -0.0% |
| RightAnti, all hits | 5.920 | 5.924 | 6.112 | +3.2% |
| Inner, all hits | 19.235 | 19.567 | 19.565 | +1.7% |
| RightSemi, high-to-low hit rate | 9.096 | 9.405 | 9.203 | +1.2% |
| RightAnti, high-to-low hit rate | 8.480 | 8.478 | 8.408 | -0.8% |
| RightSemi, single probe batch, all hits | 0.205 | 0.217 | 0.258 | +25.9% |
| RightSemi, dense 100K build, all hits | 10.172 | 10.264 | 10.107 | -0.6% |
| RightSemi, sparse 100K build, all hits | 15.579 | 15.568 | 15.567 | -0.1% |
### TPC-H with memtable
| Query | Main | Off | On | On vs main |
|---|---:|---:|---:|---:|
| Q8 | 25.332 | 23.381 | 16.080 | -36.5% |
| Q9 | 48.990 | 46.381 | 41.653 | -15.0% |
| Q17 | 67.344 | 66.039 | 43.156 | -35.9% |
### TPC-H with parquet
with the default `datafusion.execution.parquet.pushdown_filters=false`
| Query | Main | Off | On | On vs main |
| ----- | -----: | -----: | -----: | ---------: |
| Q8 | 63.736 | 63.243 | 58.271 | -8.6% |
| Q9 | 76.014 | 74.103 | 70.175 | -7.7% |
### Target HashJoin `join_time`
The following table measures the `CollectLeft` / `RightSemi` HashMap join on
`part.p_partkey = lineitem.l_partkey` described above. It reports **operator
`join_time`, summed across the four probe partitions**, separately from
end-to-end query latency.
| Input | Query | Main | Off | On | On vs main |
| ----------------- | ----- | -----: | -----: | -----: | ---------: |
| MemTable | Q8 | 29.330 | 29.625 | 12.045 | -58.9% |
| MemTable | Q9 | 39.985 | 40.010 | 26.415 | -33.9% |
| Parquet (default) | Q8 | 29.685 | 29.820 | 11.190 | -62.3% |
| Parquet (default) | Q9 | 35.830 | 35.305 | 20.525 | -42.7% |
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