Hive通过元数据库获取表的数据量，占用空间

SELECt
	a.TBL_ID,
	d.`NAME` dbName,
	a.TBL_NAME,
	b.PARAM_VALUE numRows,
	c.PARAM_VALUE totalSize
FROM
	TBLS AS a
	left JOIN TABLE_PARAMS AS b 
	on a.TBL_ID = b.TBL_ID
	left JOIN TABLE_PARAMS AS c
	on a.TBL_ID = c.TBL_ID
	left JOIN DBS as d
	on d.DB_ID = a.DB_ID
where 	 
	b.PARAM_KEY = "numRows"
	and 
	c.PARAM_KEY = "totalSize"

SELECt main.*,b.numRows,b.totalSize FROM (
	SELECt main.TBL_ID AS metaObjectId
		,main.TBL_NAME AS tabName
		,b.PART_ID AS partId
		,b.PART_NAME AS partitionName
		,b.CREATE_TIME AS createTime
		,b.LAST_ACCESS_TIME AS updateTime
	FROM TBLS main
	INNER JOIN PARTITIONS b ON main.TBL_ID = b.TBL_ID
	WHERe b.PART_NAME IS NOT NULL
) main
LEFT JOIN
(
SELECt PART_ID AS partId,
MAX(CASE PARAM_KEY WHEN 'numRows' THEN PARAM_VALUE ELSE 0 END) AS numRows,
MAX(CASE PARAM_KEY WHEN 'totalSize' THEN PARAM_VALUE ELSE 0 END) AS totalSize
FROM PARTITION_PARAMS
GROUP BY PART_ID
) b ON main.partId=b.partId;

重点：对应hive分区的几个比较重要的元数据表
TBLS：hive所有表的基础信息，包括id,表名，等等
PARTITIONS：跟分区有关的表, 包括分区id,创建时间，分区表名，以及TBLS主表关联id等等
PARTITION_PARAMS：分区表比较重要的一些数据
主要字段：
numfiles：该分区下的文件数，
numRows:该分区下记录数，
rawDataSize是指原始数据的大小，
totalSize是指占用HDFS存储空间大小，
transient_lastDdlTime最后一次ddl时间