vertica存储统计信息：
表数量：
select count(distinct table_name) FROM tables;
分区表数量：
select count(distinct table_name) from PARTITION_COLUMNS;
总表占大小：
SELECT sum(used_bytes)/1024/1024/1024 FROM projection_storage ;
分区表总大小：
select sum(disk_space_bytes)/1024/1024/1024 from PARTITION_COLUMNS;
SELECT sum(used_bytes)/1024/1024/1024 FROM projection_storage where anchor_table_name in (select distinct table_name from PARTITION_COLUMNS);
分区表大小（前10）：
select table_name,sum(disk_space_bytes)/1024/1024/1024 size from PARTITION_COLUMNS group by table_name order by size desc limit 10;
分区表每个分区的大小（前20）：
select partition_key,sum(disk_space_bytes)/1024/1024/1024 size from PARTITION_COLUMNS group by partition_key order by size desc limit 20;
