There are 3 error code types in BE: OLAPStatus AgentStatus Status.
It is very confused and sometimes conflict during write code.
I will try to unify them to Status.
This CL mainly changes:
1. Add star schema benchmark tools in `tools/ssb-tools`, for user to easy load and test with SSB data set.
2. Disable the segment cache for some read scenario such as compaction and alter operation.(Fix#6924 )
3. Fix a bug that `max_segment_num_per_rowset` won't work(Fix#6926)
4. Enable `enable_batch_delete_by_default` by default.
NOTE: This patch would modify all Backend's data.
And this will cause a very long time to restart be.
So if you want to interferer your product environment,
you should upgrade backend one by one.
1. Refactoring be is to clarify the structure the codes.
2. Use unique id to indicate a rowset.
Nameing rowset with tablet_id and version will lead to
many conflicts among compaction, clone, restore.
3. Extract an rowset interface to encapsulate rowsets
with different format.
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.
