Use packed arena tries for generic joins

[ezrosent]

This PR is part of an eight-PR stack that jointly replaces #959.

Stack base: #969

Replacement stack:

1. Add small residual join indexes #993 — small residual indexes
2. Add packed join root caches #994 — packed root caches
3. Add prepared join index state #995 — prepared index state
4. Add packed join probe abstractions #996 — packed probe abstractions
5. Add join-tail execution state #997 — join-tail execution state
6. Use packed arena tries for generic joins #998 — executor integration
7. Compact buffered free-join updates #999 — compact frame updates
8. Lazily prepare packed join state #1000 — lazy preparation

Validation on the complete stack:

• cargo fmt --check
• cargo nextest run -p egglog-core-relations
• 113 tests passed

Layer 6 of 8.

Wires the supporting abstractions into generic-join execution and switches the executor to packed arena tries. Unit tests live in a separate execute_tests.rs file; end-to-end coverage remains in the crate test module.

Diff (including tests): +3130 / -2276, net +854.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 97.90210% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.28%. Comparing base (3c94cc2) to head (eff0c6c).

Files with missing lines	Patch %	Lines
core-relations/src/free_join/residual_index.rs	81.81%	2 Missing ⚠️
core-relations/src/free_join/frame_update.rs	83.33%	1 Missing ⚠️

Additional details and impacted files

@@                           Coverage Diff                            @@
##           codex/packed-trie-split-05-join-tail     #998      +/-   ##
========================================================================
- Coverage                                 87.36%   87.28%   -0.09%     
========================================================================
  Files                                        96      101       +5     
  Lines                                     32369    33305     +936     
========================================================================
+ Hits                                      28280    29070     +790     
- Misses                                     4089     4235     +146     

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[codspeed]

Merging this PR will degrade performance by 8.68%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 2 regressed benchmarks
✅ 35 untouched benchmarks
⏩ 227 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	tests[python_array_optimize]	1.1 s	1.3 s	-10.39%
❌	tests[typeinfer]	115.8 ms	124.5 ms	-6.95%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing codex/packed-trie-split-06-executor (eff0c6c) with codex/packed-trie-split-05-join-tail (3c94cc2)}

Footnotes

1. 227 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[yihozhang]

Do we need this condition? We used to not need info.table.has_stale_rows() and instead do a filter_live() when scanning the subset.

Similarly for constraints.is_empty()

[ezrosent]

Added some tests and confirmed that this is required, as is. I agree it's a bit gross.