Optimize group by query in ClientRPCServiceImpl to reduce cpu usage

[shuwenwei]

Description

cp #15178

[codecov]

Codecov Report

Attention: Patch coverage is 10.14493% with 62 lines in your changes missing coverage. Please review.

Project coverage is 39.12%. Comparing base (726d093) to head (d4e539c).
Report is 16 commits behind head on master.

Files with missing lines	Patch %	Lines
...ecution/fragment/FakedFragmentInstanceContext.java	0.00%	40 Missing ⚠️
.../db/protocol/thrift/impl/ClientRPCServiceImpl.java	0.00%	14 Missing ⚠️
.../planner/memory/FakedMemoryReservationManager.java	0.00%	5 Missing ⚠️
...db/queryengine/execution/driver/DriverContext.java	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #15750      +/-   ##
============================================
- Coverage     39.13%   39.12%   -0.01%     
  Complexity      198      198              
============================================
  Files          4835     4837       +2     
  Lines        314362   314482     +120     
  Branches      39423    39449      +26     
============================================
+ Hits         123017   123045      +28     
- Misses       191345   191437      +92     

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[sonarqubecloud]

Quality Gate passed

Issues
7 New issues
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