feat: batching execution (single iterator queries)

[cheb0]

Description

No significant perf improvement, just introduce new types: LIDBatch, BatchedNode. Batch mode enabled for single-iterator queries for sealed fractions.

iterateEvalTree is now works with batches. For one-by-one lid we batch them a bit, for batched flow we just bypass batches as is. To batch one-by-one eval tree lids, a buffer is used. It preallocated with 64k slots.

LIDBatch currently stores lids as []uint32 sorted asc. I had to introduce an unneeded copying from LID batch format to slice of node.LID so that we have a single iterateEvalTree function. It's a cost of avoiding code duplication.

single-iterator query perf

For single-iterator query we transfer batches directly. Hot query perf service:X (hist, total is 1.6 million):

main branch:
29.578 ms

PR:
23.854 ms

stopwatch eval_tree_next fixed

As part of the PR, stopwatch usage for eval_tree_next is adrressed. For low-cardinality query service:X AND level:4 (histogram) it reports the following numbers:

Search (hot) completed. Found 100 documents. Took: 15.812 ms
total >> iterate_eval_tree >> eval_tree_next -> 95.407644ms

With this PR:
Search (hot) completed. Found 100 documents. Took: 13.958 ms
total >> iterate_eval_tree >> eval_tree_next -> 5.5113ms

Part of #329

---

• I have read and followed all requirements in CONTRIBUTING.md;
• I used LLM/AI assistance to make this pull request;

[cheb0]

@seqbenchbot up main search-keyword-exact-match-warm

[seqbenchbot]

Nice, @cheb0 <(-^,^-)=b!

Your request was successfully served.
Identificator for your ongoing benchmark - 73ed4722.

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 81.16883% with 29 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.54%. Comparing base (124d460) to head (da8604a).

Files with missing lines	Patch %	Lines
frac/processor/search.go	83.33%	9 Missing and 5 partials ⚠️
frac/sealed/lids/iterator_desc.go	69.56%	5 Missing and 2 partials ⚠️
frac/sealed/lids/iterator_asc.go	78.94%	3 Missing and 1 partial ⚠️
node/batch.go	81.81%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #390      +/-   ##
==========================================
+ Coverage   71.40%   71.54%   +0.14%     
==========================================
  Files         219      220       +1     
  Lines       16454    16568     +114     
==========================================
+ Hits        11749    11854     +105     
- Misses       3834     3840       +6     
- Partials      871      874       +3     

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[github-actions]

🔴 Performance Degradation

Some benchmarks have degraded compared to the previous run.
Click on Show table button to see full list of degraded benchmarks.

Show table

Name	Previous	Current	Ratio	Verdict
MutexListAppend-4	5115f7	f70ec9
	196.07 MB/s	177.02 MB/s	0.90	🔴

[cheb0]

@seqbenchbot down 73ed4722

[seqbenchbot]

Nice, @cheb0 <(-^,^-)=b!

The benchmark with identificator 73ed4722 was finished.
I've prepared a summary for you. Click on Show summary button to see it:

Show summary

Query	Type	mean (ms)			stddev (ms)			p(50) (ms)			p(95) (ms)			p(99) (ms)			iterations
		base	comp	diff	base	comp	diff	base	comp	diff	base	comp	diff	base	comp	diff	base	comp	diff
bulk	warm	68.99	68.64	-0.50%	24.66	24.92	+1.08%	63.00	62.00	-1.59%	118.50	117.00	-1.27%	158.50	154.00	-2.84%	2450.00	2450.00	0.00%
service:payment-backend-eu AND k8s_namespace:prod	warm	123.87	124.02	+0.12%	113.56	116.60	+2.68%	115.00	113.00	-1.74%	223.00	221.00	-0.90%	731.50	759.50	+3.83%	3979.00	3958.00	-0.53%

Have a great time!

[github-actions]

🔴 Performance Degradation

Some benchmarks have degraded compared to the previous run.
Click on Show table button to see full list of degraded benchmarks.

Show table

Name	Previous	Current	Ratio	Verdict
MutexListAppend-4	5115f7	c14eb6
	196.07 MB/s	163.95 MB/s	0.84	🔴
	83287562.00 ns/op	97590828.00 ns/op	1.17	🔴