Refactor results trimming to avoid rebuilding the maps. #5
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One of the hottest parts of the code which is doing the GroupBy operation is needlessly recreating a HashMap in the most common case. This change flips the data structure for intermediate results around to take advantage of more optimal results trimming. If the results don't have to be trimmed the original produced Map is simply returned back.
Todo:
Performance measurement results:
Machine configuration:
4 core (8 threads) Intel(R) Xeon(R) W-2123 CPU @ 3.60GHz
32GB of RAM
Linux x86-64, kernel: 5.0.0-37-generic
Benchmark configuration:
TPC-H (optimal index)
20 clients
180s runtime
Results (QPS higher is better, response time lower is better)
Base with (resuse-bytebuffer):
180.013s, Query Executed: 567074, QPS: 3150.1835978512663, Avg Response Time: 6.337580280527762ms
Improved (this branch):
Time Passed: 180.013s, Query Executed: 617034, QPS: 3427.7191091754485, Avg Response Time: 5.82426738234846ms
Co-authored-by: @grcevski @charliegracie @macarte @adityamandaleeka