Hive：查看表統計信息

概述

在Hive數據庫中對SQL進行調優的時候，往往需要了解表的統計信息，比如：分區數量，數據行數，表的大小，文件個數等等。獲取Hive表統計信息之前，需要先對Hive表收集統計信息：

• 非分區表
  ANALYZE TABLE table_name COMPUTE STATISTICS;
• 分區表
  ANALYZE TABLE table_name PARTITION(partition_col='partition_value') COMPUTE STATISTICS;
  下面提供兩種方式來獲取Hive表的統計信息。

方式一

方式一比較簡單，只需執行命令DESC FORMATTED table_name;即可。

方式二

方式二需要開發者具有連接Hive元數據數據庫的權限，使用SQL語句來獲取統計信息。

• 非分區表

SELECT    b.tbl_name                                                                                  AS '表名'
        , SUM(CASE WHEN a.param_key = 'numRows' THEN a.param_value ELSE 0 END)                        AS '表數據行'
        , SUM(CASE WHEN a.param_key = 'numRows' THEN 1 ELSE 0 END)                                    AS '表分區數'
        , SUM(CASE WHEN a.param_key = 'totalSize' THEN a.param_value ELSE 0 END) / 1024 / 1024 / 1024 AS '數據量GB'
        , SUM(CASE WHEN a.param_key = 'numFiles' THEN a.param_value ELSE 0 END)                       AS '文件數'
FROM    TABLE_PARAMS a
JOIN    TBLS b
ON      a.tbl_id = b.tbl_id
WHERE   b.tbl_name IN ('table_name')
AND     b.owner = 'hive'
;

• 分區表

SELECT    c.tbl_name                                                                                  AS '表名'
        , SUM(CASE WHEN b.param_key = 'numRows' THEN b.param_value ELSE 0 END)                        AS '表數據行'
        , SUM(CASE WHEN b.param_key = 'numRows' THEN 1 ELSE 0 END)                                    AS '表分區數'
        , SUM(CASE WHEN b.param_key = 'totalSize' THEN b.param_value ELSE 0 END) / 1024 / 1024 / 1024 AS '數據量GB'
        , SUM(CASE WHEN b.param_key = 'numFiles' THEN b.param_value ELSE 0 END)                       AS '文件數'
FROM    PARTITIONS a
JOIN    PARTITION_PARAMS b
ON      a.part_id = b.part_id
JOIN    TBLS c
ON      a.tbl_id = c.tbl_id
WHERE   c.tbl_name IN ('table_name')
AND     c.owner = 'hive'
GROUP BY c.tbl_name
;