[damccorm]

Description

Optimizes AbstractComponentCoderImpl.estimate_size, TupleCoderImpl, and SequenceCoderImpl in sdks/python/apache_beam/coders/coder_impl.py and sdks/python/apache_beam/coders/coder_impl.pxd:

1. AbstractComponentCoderImpl.get_estimated_size_and_observables: Types loop variables (i=int, last=int, num_coders=int) in coder_impl.pxd, guards if child_observables: observables += child_observables to avoid extending an empty list on every component, and forwards nested=nested from estimate_size.
2. TupleCoderImpl._extract_components and _construct_from_components: Avoids copying tuple(value) / tuple(components) when the input is already a tuple (or list for extraction).
3. SequenceCoderImpl.encode_to_stream: Short-circuits type(value) is tuple or type(value) is list before calling hasattr(value, "__len__").

Benchmarks & Performance Impact

• Isolated Microbenchmark Rerun (upstream/master vs upstream/master + this PR alone): bench_18_tuple_and_sequence_coder_impl (c2feb961eef) (on branch perf/py-benchmarks-suite) — 300,000 SequenceCoderImpl.encode and TupleCoderImpl.estimate_size calls improved from 209.90 ms -> 148.70 ms (1.41x faster, -29.2%, -61.20 ms) in compiled Cython.
• Per-Change Attribution (Most to Least Impact, 300,000 calls each in compiled Cython):
  1. Most impact (79.4% of savings, -41.63 ms): Optimizing AbstractComponentCoderImpl.get_estimated_size_and_observables (if child_observables: guard, typed loop locals, and TupleCoderImpl._extract_components tuple pass-through) — 126.00 ms -> 84.37 ms (1.49x faster, -33.0%).
  2. Least impact (20.6% of savings, -10.81 ms): Short-circuiting type(value) is tuple or type(value) is list before hasattr(value, "__len__") in SequenceCoderImpl.encode_to_stream — 63.62 ms -> 52.81 ms (1.20x faster, -17.0%).
• End-to-End Cloud Dataflow Benchmark (core_window_row_combine): Included in run_core_window_row_combine_pipeline (c2feb961eef) (3,000,000 generated events -> 9,000,000 sliding-windowed elements on a single n2-standard-4 worker), which improved end-to-end worker stage execution time by 1.80x (-44.5%, 599.6s -> 332.9s) and reduced total billable Dataflow vCPU/Memory/PD usage by -26.1% (1,134 -> 838 vCPU-s).

Testing

• Verified with pytest sdks/python/apache_beam/coders/coders_test.py sdks/python/apache_beam/coders/fast_coders_test.py.

[damccorm]

/gemini review

[github-actions]

📋 Review Summary

This PR introduces targeted Cython and Python fast-path optimizations for AbstractComponentCoderImpl, TupleCoderImpl, and SequenceCoderImpl, along with fixing AbstractComponentCoderImpl.estimate_size to forward the nested parameter. The changes are clean, preserve coder semantics, and are well-supported by microbenchmark and end-to-end Dataflow benchmark results.

🔍 General Feedback

• The fast paths for tuple/list checks and the if child_observables: guard in AbstractComponentCoderImpl.get_estimated_size_and_observables translate directly into fast C-level checks in Cython without unnecessary allocations or attribute lookups.
• One minor accidental change in coder_impl.pxd on WindowedValueCoderImpl.get_estimated_size_and_observables is noted inline.

---

💡 Tip: Comment /gemini review on this pull request to trigger a new Gemini code review.

[github-actions]

🟢 Low: WindowedValueCoderImpl.get_estimated_size_and_observables does not use i, last, or num_coders. It looks like this @cython.locals decorator was unintentionally updated alongside AbstractComponentCoderImpl.get_estimated_size_and_observables.

Suggested change

	@cython.locals(c=CoderImpl, i=int, last=int, num_coders=int)
	@cython.locals(c=CoderImpl)

[damccorm]

Fixed in 91f182a: reverted @cython.locals on WindowedValueCoderImpl.get_estimated_size_and_observables back to @cython.locals(c=CoderImpl).

[damccorm]

/gemini review

[github-actions]

📋 Review Summary

This PR introduces targeted Cython and hot-path optimizations to AbstractComponentCoderImpl, TupleCoderImpl, and SequenceCoderImpl in coder_impl.py and coder_impl.pxd. The changes are clean, preserve existing semantics (while fixing nested forwarding in AbstractComponentCoderImpl.estimate_size), and address the previous review feedback.

🔍 General Feedback

• Typing the loop variables (i, last, num_coders) in AbstractComponentCoderImpl.get_estimated_size_and_observables and guarding observables += child_observables cleanly avoids unnecessary Cython object overhead and empty list extensions.
• Fast-pathing tuple and list checks in TupleCoderImpl and SequenceCoderImpl.encode_to_stream avoids redundant allocations and attribute lookups in tight encoding/estimation loops.
• Forwarding nested=nested in AbstractComponentCoderImpl.estimate_size ensures accurate size estimation for nested variable-length last components.

---

💡 Tip: Comment /gemini review on this pull request to trigger a new Gemini code review.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.63%. Comparing base (d3078c1) to head (91f182a).
⚠️ Report is 83 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #41217      +/-   ##
============================================
+ Coverage     57.48%   57.63%   +0.15%     
  Complexity     2492     2492              
============================================
  Files          1204     1198       -6     
  Lines        171265   171203      -62     
  Branches       2103     2103              
============================================
+ Hits          98456    98680     +224     
+ Misses        70157    69871     -286     
  Partials       2652     2652              

Flag	Coverage Δ
python	80.54% <100.00%> (+0.32%)	⬆️

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