* Change label of broker load txn
1. put broker load label into txn label
2. fix the bug of `label is already used`
3. fix partition error of new broker load
* Fix count error in mini load and broker load
There are three params (num_rows_load_total, num_rows_load_filtered, num_rows_load_unselected) which are used to count dpp.norm.ALL and dpp.abnorm.ALL.
num_rows_load_total is the number rows of source file.
num_rows_load_unselected is the not satisfied (where conjuncts) rows of num_rows_load_total
num_rows_load_filtered is the rows (quality not good enough) of (num_rows_load_total-num_rows_load_unselected)
1. Add broker load error hub
A broker load error hub will collect error messages in load process and saves them as a file to the specified remote storage via broker. In case that in broker/min/streaming load process, user may not be able to access the error log file in Backend directly.
We also add a new header option: 'enable_hub' in streaming load request, and default is false. Because if we enable the broker load error hub, it will significantly slow down the processing speed of streaming load, due to the visit of remote storage via broker. So use can disable the error load hub using this header option, to avoid slowing down the load speed.
2. Show load error logs by using SHOW LOAD WARNINGS stmt
We also provide a more easy way to get load error logs. We implement 'SHOW LOAD WARNINGS ON 'url'' stmt to show load error logs directly. The 'url' in stmt is provided in 'SHOW LOAD' stmt.
eg:
show load warnings on "http://192.168.1.1:8040/api/_load_error_log?file=__shard_2/error_log_xxx";
3. Support now() function in broker load
User can mapping a column to now() in broker load stmt, which means this column will be filled with time when the ETL started.
4. Support more types of wildcard in broker load
Currently, we only support wildcard '*' to match the file names. wildcard like '/path/to/20190[1-4]*' is not support.
1. ix bugs in query layer.
2. remove some redundant code in BE
3. support specify multi helper node when starting FE
4. add proc 'cluster_load_statistic' to show load balance situation of Palo
