[8.4] MOD-14063: Fix FILTER bug with multiple indexes with the same field aliases

[raz-mon]

Summary

Backport of commit 9c70952 from master to 8.4 branch.

This PR fixes a bug where the FILTER expression evaluation was incorrectly sharing field aliases between multiple indexes, causing incorrect indexing behavior.

Related Jira: MOD-14334
Original PR: #8396

Conflicts Resolved

The following conflicts were encountered during the cherry-pick and resolved as follows:

1. src/rlookup.c

• Conflict: The master branch uses _head/_tail naming convention for RLookup struct members while the 8.4 branch uses head/tail.
• Resolution: Kept the 8.4 branch naming convention (head/tail) as this is consistent with the existing codebase in this branch. Also kept the memset(lk, 0, sizeof(*lk)) from the incoming change (important for the fix).

2. tests/pytests/test_followhashes.py

• Conflict: The 8.4 branch contains additional tests that were backported separately (testCountry, testIssue1571, testIssue1571WithRename, testIdxFieldJson, testFilterStartWith, testFilterWithOperator, testFilterWithNot) which were not present in the original commit.
• Resolution: Preserved all existing 8.4 tests (HEAD version) since these tests are valid and were added as part of previous backports or branch-specific changes.

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Pull Request opened by Augment Code with guidance from the PR author

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Note

Medium Risk
Touches indexing-time FILTER evaluation and RLookup lifecycle/reset logic; incorrect cleanup could cause missed/extra indexing or memory issues, though changes are localized and covered by new tests.

Overview
Fixes a bug where FILTER expressions could reuse stale RLookup/row state across multiple index evaluations, leading to incorrect indexing when indexes share field aliases.

The filter-evaluation loop now explicitly resets lookup/row state between indexes, and RLookup cleanup/reset is hardened (clear struct to zero, null dyn after free, add an assertion on ndyn). Adds a dedicated test_filter.py suite (and moves prior filter tests out of test_followhashes.py) to cover multi-index/alias scenarios and related filter behavior.

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[jit-ci]

🛡️ Jit Security Scan Results

✅ No security findings were detected in this PR

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^{Security scan by Jit}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.50%. Comparing base (b66b4e3) to head (5fde59b).
⚠️ Report is 1 commits behind head on 8.4.

Additional details and impacted files

@@            Coverage Diff             @@
##              8.4    #8596      +/-   ##
==========================================
- Coverage   85.54%   85.50%   -0.05%     
==========================================
  Files         337      337              
  Lines       53353    53356       +3     
  Branches    11023    11023              
==========================================
- Hits        45642    45620      -22     
- Misses       7568     7593      +25     
  Partials      143      143              

Flag	Coverage Δ
flow	85.17% <100.00%> (+0.59%)	⬆️
unit	51.06% <60.00%> (-0.02%)	⬇️

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[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[raz-mon]

Approved by me.