fix: values of bigint columns in cartesian product might be string

[cyjake]

att

[Copilot]

Pull Request Overview

This PR fixes an issue where bigint columns in cartesian product joins might be returned as strings, causing strict equality comparisons to fail when checking for duplicate primary keys.

• Changes strict equality (===) to loose equality (==) for primary key comparison in join operations
• Adds explanatory comments about the bigint/string conversion issue with MySQL's supportBigNumbers option

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.77%. Comparing base (d14ae63) to head (0ebe597).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #440   +/-   ##
=======================================
  Coverage   96.77%   96.77%           
=======================================
  Files          45       45           
  Lines        3719     3719           
  Branches       73       73           
=======================================
  Hits         3599     3599           
  Misses        106      106           
  Partials       14       14           

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