Some SQL will take up too much memory in the application, the
service is not stable, after analysis because the SQL query need to scan the
relevant segemnt corresponding hbase table, is through the thread asynchronous
request related to SQL cuboid corresponding region. After each segment makes a
request, wait for the data to process the hbase callbacks.
But sometimes SQL involves more segments, and before all the segments make
requests, there is a large amount of data returned, leading to memory alarm and