fix(tianmu): fix error occurred in the union all query result (#1599)

[adofsauron]

Summary about this PR

Issue Number: close #1599

Tests Check List

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Changelog

• New Feature
• Bug Fix
• Performance Improvement
• Build/Testing/CI/CD
• Documentation
• Not for changelog (changelog entry is not required)

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features

[mergify]

Thanks for the contribution!
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Please review the labels and make any necessary changes.

[konghaiya]

LGTM

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.03 ⚠️

Comparison is base (74b5b05) 55.18% compared to head (5817acf) 55.16%.

❗ Current head 5817acf differs from pull request most recent head 31ae1c3. Consider uploading reports for the commit 31ae1c3 to get more accurate results

Additional details and impacted files

@@                 Coverage Diff                 @@
##           stonedb-5.7-dev    #1750      +/-   ##
===================================================
- Coverage            55.18%   55.16%   -0.03%     
===================================================
  Files                 2031     2031              
  Lines               431436   431443       +7     
===================================================
- Hits                238081   237986      -95     
- Misses              193355   193457     +102     

Impacted Files	Coverage Δ
storage/tianmu/core/engine.h	29.16% <ø> (ø)
storage/tianmu/core/engine_results.cpp	85.84% <100.00%> (+0.31%)	⬆️

... and 59 files with indirect coverage changes

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