fix(query): preserve subquery limit after offset skips

[QuantumExplorer]

Summary

• only decrement the outer limit for an empty subquery result when no rows were skipped by offset
• add forward and reverse regressions where offset consumes the first inner result before limit accounting begins

Fixes #690.

Verification

• cargo test -p grovedb subquery_offset_consumed_empty --lib
• cargo test -p grovedb test_get_range_query_with_unique_subquery --lib
• cargo test -p grovedb query_tests --lib

Summary by CodeRabbit

• Bug Fixes

  • Fixed query limit behavior when subqueries return empty results, improving consistency across protocol versions.

• Tests

  • Added test coverage for query offset and limit interactions under different protocol configurations.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: fdb3ec7e-bf3e-452f-9848-d192ababb0ca

📥 Commits

Reviewing files that changed from the base of the PR and between a2129a9 and 5687dce.

📒 Files selected for processing (3)

• grovedb-version/src/version/v3.rs
• grovedb/src/element/query.rs
• grovedb/src/tests/query_tests.rs

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📝 Walkthrough

Walkthrough

Protocol version v3 now enables path_query_push v1, which implements versioned behavior for subquery offset/limit handling. The query logic conditionally gates limit decrement on version and skipped count to fix offset-consumed-empty subquery behavior; three new tests validate both v1 and legacy v0 modes.

Changes

Subquery Offset-Consumed-Empty Limit Fix

Layer / File(s)	Summary
Version contract and query logic versioning grovedb-version/src/version/v3.rs, grovedb/src/element/query.rs	GROVE_V3 bumps path_query_push to version 1. Query logic reads this version, validates with check_grovedb_v0_or_v1_with_cost!, and gates the limit-decrement behavior in empty-subquery branches on path_query_push_version == 0 || skipped == 0.
Forward, reverse, and legacy version test coverage grovedb/src/tests/query_tests.rs	Three tests validate offset-consumed-empty behavior: forward and reverse direction with v1 expect two returned elements and skipped = 1 without limit decrease; legacy v0 test expects one element with the original decrement behavior.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 A subquery offset once played a trick,
Consuming the limit, oh how quick!
Now versioned in v3, the fix rings true—
Skip-aware decrement, a behavior made new! 🌿

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main fix: preserving subquery limit after offset skips, which directly addresses the core issue in the PR.
Linked Issues check	✅ Passed	The PR implements the exact fix suggested in issue #690: only decrement the outer limit when no rows were skipped by offset, with new forward/reverse tests.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing issue #690: version bump for path_query_push, conditional limit decrement logic, and regression tests.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/fix-690-subquery-offset-limit

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.43%. Comparing base (60f2968) to head (5687dce).
⚠️ Report is 3 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #730      +/-   ##
===========================================
+ Coverage    91.42%   91.43%   +0.01%     
===========================================
  Files          236      236              
  Lines        67053    67116      +63     
===========================================
+ Hits         61305    61370      +65     
+ Misses        5748     5746       -2     

Components	Coverage Δ
grovedb-core	88.95% <100.00%> (+<0.01%)	⬆️
merk	92.26% <ø> (ø)
storage	86.36% <ø> (ø)
commitment-tree	96.43% <ø> (ø)
mmr	96.79% <ø> (+0.03%)	⬆️
bulk-append-tree	89.39% <ø> (+0.13%)	⬆️
element	97.38% <ø> (+0.01%)	⬆️

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