我们如何知道表是托管表还是外部表？

Question

在hive中，当我运行show tables;时，我得到了所有表的列表，我如何知道哪些是托管表，哪些是外部表？

Answer 1

对于单个表格，您可以使用desc formatted或desc extended

演示

create table mytable (i int);
create external table myexttable (i int);

desc格式化

hive> desc formatted mytable;
...
Location:               hdfs://horton/user/dmarkovitz/mytable
Table Type:             MANAGED_TABLE
Table Parameters:
...

hive> desc formatted myexttable;

...
Location:               hdfs://horton/user/dmarkovitz/myexttable
Table Type:             EXTERNAL_TABLE
Table Parameters:
...

desc extended

hive> desc extended mytable;
...
Detailed Table Information      Table(tableName:mytable ... tableType:MANAGED_TABLE)

hive> desc extended myexttable;
...
Detailed Table Information      Table(tableName:myexttable ... tableType:EXTERNAL_TABLE)

对于许多/所有表，您可以查询Metastore（Hive元数据数据库）。

metastore

（在本演示中，Metastore是在mysql中）

select  d.name          as database_name
       ,t.tbl_name
       ,t.tbl_type

from            metastore.DBS   as d

        join    metastore.TBLS  as t  

        on      t.DB_ID =
                d.DB_ID

where   d.name = 'dmarkovitz'
;

+---------------+------------+----------------+
| database_name |  tbl_name  |    tbl_type    |
+---------------+------------+----------------+
| dmarkovitz    | mytable    | MANAGED_TABLE  |
| dmarkovitz    | myexttable | EXTERNAL_TABLE |
+---------------+------------+----------------+

仅供参考，EXTERNAL / MANAGED属性只是一个标志（元数据级别），可以使用ALTER TABLE命令进行更改

<强>蜂房

alter table mytable set tblproperties ("EXTERNAL"="TRUE");
alter table myexttable set tblproperties ("EXTERNAL"="FALSE");

<强> metastore

select  d.name          as database_name
       ,t.tbl_name
       ,t.tbl_type

from            metastore.DBS   as d

        join    metastore.TBLS  as t  

        on      t.DB_ID =
                d.DB_ID

where   d.name = 'dmarkovitz'
;

+---------------+------------+----------------+
| database_name |  tbl_name  |    tbl_type    |
+---------------+------------+----------------+
| dmarkovitz    | mytable    | EXTERNAL_TABLE |
| dmarkovitz    | myexttable | MANAGED_TABLE  |
+---------------+------------+----------------+

Answer 2

您可以使用以下命令获取指定表的详细信息：

describe formatted <your_table>;

输出将包含一行描述table type：

  

表类型：EXTERNAL_TABLE

或

  

表类型：MANAGED_TABLE