trgfree

### **it seems that lack the file benchmark/benchmark.h** make benchmark g++ -std=c++17 -Wall -Isrc/ -L./ -O3 benchmark/benchmark.cpp benchmark/benchmark_utils.cpp benchmark/parser_benchmark.cpp benchmark/queries.cpp -o bin/benchmark -lbenchmark -lpthread -lsqlparser -lstdc++ -lstdc++fs benchmark/benchmark.cpp:1:10: fatal error:...

there is a bug in purge_relay_logs. It leads to can't use the option of use_hard_link。 the option named use_hardlink，but when it is used as use_hard_link。so the option isn't used at...