1. Replace std::max with a ternary expression, std::max is much heavier than the ternary operator
2. Replace std::set with arrays, std::set is based on red-black trees, traversal will follow the chain domain, and cache hits are not good
3. Optimize the serialize function, improve the calculation speed of num_non_zero_registers by reducing branches, and the serialization of _registers after optimization is faster
4. The test found that the performance improvement is more obvious
This commit enable the avg operator in fe instead of converting the avg function into sum/count.
Also, this commit fix the bug of deciamlv2 avg which cause the core in be.
The int128 could not be assinged directly.
The speed of avg function is similar to sum function after enhancement.
2. add 2 new proc '/current_queries' and '/current_backend_instances' to monitor the current running queries.
3. add a manual compaction api on Backend to trigger cumulative or base compaction manually.
4. add Frontend config 'max_bytes_per_broker_scanner' to limit to bytes per one broker scanner. This is to limit the memory cost of a single broker load job
5. add Frontend config 'max_unfinished_load_job' to limit load job number: if number of running load jobs exceed the limit, no more load job is allowed to be submmitted.
6. a log of bug fixed
1. Apache HDFS broker support HDFS HA and Hadoop kerberos authentication.
2. New Backup and Restore function. Use Fs Broker to backup your data to HDFS or restore them from HDFS.
3. Table-Level Privileges. Grant fine-grained privileges on table-level to specified user.
4. A lot of bugs fixed.
5. Performance improvement.
