Push down hash table references from HashJoinExec into scans using CASE structure

[adriangb]

This is a WIP PR just to run some benchmarks, it is not ready for review
It was mostly AI generated with the goal of running benchmarks not to make a mergeable change

[adriangb]

Here's some initial results:

❯ cargo run --release -p datafusion-cli -- -f q.sql
    Finished `release` profile [optimized] target(s) in 0.47s
     Running `target/release/datafusion-cli -f q.sql`
DataFusion CLI v50.3.0
+-------+
| count |
+-------+
| 1000  |
+-------+
1 row(s) fetched. 
Elapsed 0.006 seconds.

0 row(s) fetched. 
Elapsed 0.001 seconds.

+-----------+
| count     |
+-----------+
| 100000000 |
+-----------+
1 row(s) fetched. 
Elapsed 1.746 seconds.

0 row(s) fetched. 
Elapsed 0.001 seconds.

+----+----+----+
| k  | v  | k  |
+----+----+----+
| 50 | 50 | 50 |
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| .            |
| .            |
| .            |
+----+----+----+
951 row(s) fetched. (First 40 displayed. Use --maxrows to adjust)
Elapsed 0.004 seconds.


datafusion on  pushdown-hashes-case [?] is 📦 v50.3.0 via 🐍 v3.13.7 (datafusion-benchmark) via 🦀 v1.90.0 on ☁️  [email protected](us-east4) took 3s 
❯ datafusion-cli -f q.sql                          
DataFusion CLI v50.0.0
+-------+
| count |
+-------+
| 1000  |
+-------+
1 row(s) fetched. 
Elapsed 0.065 seconds.

0 row(s) fetched. 
Elapsed 0.004 seconds.

+-----------+
| count     |
+-----------+
| 100000000 |
+-----------+
1 row(s) fetched. 
Elapsed 1.531 seconds.

0 row(s) fetched. 
Elapsed 0.001 seconds.

+----+----+----+
| k  | v  | k  |
+----+----+----+
| 50 | 50 | 50 |
| 51 | 51 | 51 |
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| 89 | 89 | 89 |
| .            |
| .            |
| .            |
+----+----+----+
951 row(s) fetched. (First 40 displayed. Use --maxrows to adjust)
Elapsed 0.136 seconds.


datafusion on  pushdown-hashes-case [?] is 📦 v50.3.0 via 🐍 v3.13.7 (datafusion-benchmark) via 🦀 v1.90.0 on ☁️  [email protected](us-east4) 
❯ ./benchmarks/bench.sh compare main pushdown-hashes-case
Comparing main and pushdown-hashes-case
--------------------
Benchmark tpch_sf10.json
--------------------
┏━━━━━━━━━━━━━━┳━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━┓
┃ Query        ┃       main ┃ pushdown-hashes-case ┃        Change ┃
┡━━━━━━━━━━━━━━╇━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━┩
│ QQuery 1     │  495.39 ms │            443.15 ms │ +1.12x faster │
│ QQuery 2     │   94.35 ms │             86.27 ms │ +1.09x faster │
│ QQuery 3     │  255.05 ms │            248.12 ms │     no change │
│ QQuery 4     │  209.80 ms │            196.09 ms │ +1.07x faster │
│ QQuery 5     │  375.67 ms │            349.27 ms │ +1.08x faster │
│ QQuery 6     │  146.43 ms │            133.02 ms │ +1.10x faster │
│ QQuery 7     │  573.03 ms │            505.02 ms │ +1.13x faster │
│ QQuery 8     │  434.82 ms │            366.27 ms │ +1.19x faster │
│ QQuery 9     │  653.18 ms │            558.85 ms │ +1.17x faster │
│ QQuery 10    │  359.55 ms │            330.17 ms │ +1.09x faster │
│ QQuery 11    │   77.48 ms │             66.45 ms │ +1.17x faster │
│ QQuery 12    │  204.63 ms │            188.96 ms │ +1.08x faster │
│ QQuery 13    │  359.42 ms │            345.62 ms │     no change │
│ QQuery 14    │  178.11 ms │            178.12 ms │     no change │
│ QQuery 15    │  260.67 ms │            258.49 ms │     no change │
│ QQuery 16    │   64.22 ms │             66.97 ms │     no change │
│ QQuery 17    │  656.44 ms │            703.65 ms │  1.07x slower │
│ QQuery 18    │ 1193.44 ms │           1072.72 ms │ +1.11x faster │
│ QQuery 19    │  293.48 ms │            285.36 ms │     no change │
│ QQuery 20    │  236.95 ms │            235.57 ms │     no change │
│ QQuery 21    │  706.11 ms │            692.01 ms │     no change │
│ QQuery 22    │   84.61 ms │             84.55 ms │     no change │
└──────────────┴────────────┴──────────────────────┴───────────────┘
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━┓
┃ Benchmark Summary                   ┃           ┃
┡━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━┩
│ Total Time (main)                   │ 7912.82ms │
│ Total Time (pushdown-hashes-case)   │ 7394.69ms │
│ Average Time (main)                 │  359.67ms │
│ Average Time (pushdown-hashes-case) │  336.12ms │
│ Queries Faster                      │        12 │
│ Queries Slower                      │         1 │
│ Queries with No Change              │         9 │
│ Queries with Failure                │         0 │
└─────────────────────────────────────┴───────────┘

Where q.sql is basically https://datafusion.apache.org/blog/2025/09/10/dynamic-filters/#hash-join-dynamic-filters