fix(tianmu): Avoid OOM when data too large and aggregated (#949)

[adofsauron]

1. Use memory mapping
2. Set the maximum number of concurrent threads for aggregation

Summary about this PR

Issue Number: close #949 #1291

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!
I have applied any labels matching special text in your PR Changelog.

Please review the labels and make any necessary changes.

[codecov]

Codecov Report

Patch coverage: 69.79% and project coverage change: +0.04 🎉

Comparison is base (106431a) 42.89% compared to head (db55498) 42.93%.

❗ Current head db55498 differs from pull request most recent head c2c0676. Consider uploading reports for the commit c2c0676 to get more accurate results

Additional details and impacted files

@@                 Coverage Diff                 @@
##           stonedb-5.7-dev    #1355      +/-   ##
===================================================
+ Coverage            42.89%   42.93%   +0.04%     
===================================================
  Files                 1836     1838       +2     
  Lines               397300   397390      +90     
===================================================
+ Hits                170411   170621     +210     
+ Misses              226889   226769     -120     

Impacted Files	Coverage Δ
storage/tianmu/core/aggregation_algorithm.h	60.00% <ø> (ø)
storage/tianmu/core/engine.h	30.43% <ø> (ø)
storage/tianmu/handler/ha_tianmu.cpp	54.24% <0.00%> (+4.29%)	⬆️
storage/tianmu/mm/memory_handling_policy.cpp	47.56% <0.00%> (+0.23%)	⬆️
storage/tianmu/system/configuration.cpp	100.00% <ø> (ø)
storage/tianmu/system/configuration.h	0.00% <ø> (ø)
storage/tianmu/core/aggregation_algorithm.cpp	55.95% <30.00%> (-0.03%)	⬇️
storage/tianmu/mm/huge_heap_policy.cpp	41.66% <44.44%> (+1.66%)	⬆️
storage/tianmu/core/engine.cpp	51.31% <81.81%> (+2.71%)	⬆️
storage/tianmu/mm/memory_statistics.h	86.79% <86.79%> (ø)
... and 1 more

... and 27 files with indirect coverage changes

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.