UBarney opened a new pull request, #19602:
URL: https://github.com/apache/datafusion/pull/19602
## Which issue does this PR close?
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- Closes #.
## Rationale for this change
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The previous implementation of `HashTableLookupExpr::evaluate` relied on
per-row calls to `get_matched_indices`, which introduced significant
performance bottlenecks:
1. **High Memory Overhead**: Each per-row call triggered small `Vec`
allocations and potential resizes, leading to excessive pressure on the memory
allocator.
2. **Redundant Computation**: `get_matched_indices` traverses the entire
hash chain to find all matches, which is unnecessary when we only need to
verify the existence of a key.
## Performance Results (TPC-H)
The following TPC-H results were obtained with
**`DATAFUSION_EXECUTION_PARQUET_PUSHDOWN_FILTERS=true`:**
```
┏━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━┳━━━━━━━━━━━━━━━┓
┃ Query ┃ baseline@9a9ff ┃ optimized ┃ Change ┃
┡━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━╇━━━━━━━━━━━━━━━┩
│ QQuery 1 │ 679.51 ms │ 728.06 ms │ 1.07x slower │
│ QQuery 2 │ 388.33 ms │ 384.11 ms │ no change │
│ QQuery 3 │ 864.38 ms │ 856.27 ms │ no change │
│ QQuery 4 │ 458.46 ms │ 468.26 ms │ no change │
│ QQuery 5 │ 1614.26 ms │ 1525.65 ms │ +1.06x faster │
│ QQuery 6 │ 611.20 ms │ 610.06 ms │ no change │
│ QQuery 7 │ 950.39 ms │ 940.13 ms │ no change │
│ QQuery 8 │ 1214.86 ms │ 1218.21 ms │ no change │
│ QQuery 9 │ 2657.61 ms │ 2482.09 ms │ +1.07x faster │
│ QQuery 10 │ 1050.70 ms │ 1001.96 ms │ no change │
│ QQuery 11 │ 383.92 ms │ 347.27 ms │ +1.11x faster │
│ QQuery 12 │ 963.14 ms │ 920.78 ms │ no change │
│ QQuery 13 │ 473.68 ms │ 480.97 ms │ no change │
│ QQuery 14 │ 363.36 ms │ 345.27 ms │ no change │
│ QQuery 15 │ 960.56 ms │ 955.05 ms │ no change │
│ QQuery 16 │ 281.95 ms │ 267.34 ms │ +1.05x faster │
│ QQuery 17 │ 5306.43 ms │ 4983.21 ms │ +1.06x faster │
│ QQuery 18 │ 3415.11 ms │ 3016.52 ms │ +1.13x faster │
│ QQuery 19 │ 761.67 ms │ 759.49 ms │ no change │
│ QQuery 20 │ 650.20 ms │ 642.40 ms │ no change │
│ QQuery 21 │ 3111.85 ms │ 2833.05 ms │ +1.10x faster │
│ QQuery 22 │ 141.75 ms │ 143.06 ms │ no change │
└──────────────┴────────────────┴────────────┴───────────────┘
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━┓
┃ Benchmark Summary ┃ ┃
┡━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━┩
│ Total Time (baseline@9a9ff) │ 27303.30ms │
│ Total Time (optimized) │ 25909.21ms │
│ Average Time (baseline@9a9ff) │ 1241.06ms │
│ Average Time (optimized) │ 1177.69ms │
│ Queries Faster │ 7 │
│ Queries Slower │ 1 │
│ Queries with No Change │ 14 │
│ Queries with Failure │ 0 │
└───────────────────────────────┴────────────┘
```
Note that Q1 does not involve `HashJoin`.
### Note on Configuration
Benchmarks were conducted with
`DATAFUSION_EXECUTION_PARQUET_PUSHDOWN_FILTERS=true` because
`HashTableLookupExpr::evaluate` is **NOT** invoked under default settings.
I manually added `dbg!(&num_rows)` at [L335 in
`partitioned_hash_eval.rs`](https://github.com/apache/datafusion/blob/9a9ff8d6162b7391736b0b7c82c00cb35b0652a1/datafusion/physical-plan/src/joins/hash_join/partitioned_hash_eval.rs#L335)
and confirmed that the logic path is only triggered when this flag is enabled.
Under default settings, `HashTableLookupExpr::evaluate` is not called; . I am
uncertain if this current behavior is intentional.
## What changes are included in this PR?
- Added `JoinHashMapType::set_bits_if_exists`: A new trait method that
processes
a batch of hashes and updates a bitmask for existing keys.
- Refactored `HashTableLookupExpr::evaluate`: Switched from per-row lookups
to
the new batch API.
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## Are these changes tested?
Yes
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## Are there any user-facing changes?
NO
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