View 在配置单元表上创建视图:丢失每个变量的注释
我创建了一个配置单元表,我们在“注释”字段中为每个变量添加了一些描述,如下所示:View 在配置单元表上创建视图:丢失每个变量的注释,view,hive,pyspark,comments,View,Hive,Pyspark,Comments,我创建了一个配置单元表,我们在“注释”字段中为每个变量添加了一些描述,如下所示: spark.sql("create table test_comment (col string comment 'col comment') comment 'hello world table comment ' ") spark.sql("describe test_comment").show() +--------+---------+-----------+ |col_name|data_type|
spark.sql("create table test_comment (col string comment 'col comment') comment 'hello world table comment ' ")
spark.sql("describe test_comment").show()
+--------+---------+-----------+
|col_name|data_type| comment|
+--------+---------+-----------+
| col| string|col comment|
+--------+---------+-----------+
一切都很好,我们在变量“col”的起始字段中看到注释“col comment”
现在,当我在此表上创建视图时,“comment”字段不会传播到视图,“comment”列为空:
spark.sql("""create view test_comment_view as select * from test_comment""")
spark.sql("describe test_comment_view")
+--------+---------+-------+
|col_name|data_type|comment|
+--------+---------+-------+
| col| string| null|
+--------+---------+-------+
在创建视图时,是否有方法保留注释字段的值?这一“特征”的原因是什么
我正在使用:
Hadoop 2.6.0-cdh5.8.0
蜂巢1.1.0-cdh5.8.0
Spark 2.1.0.cloudera1我观察到,即使从另一个表创建表,注释也不会继承。看起来这是默认行为
create table t1 like another_table
desc t1 //includes comments
+-----------+------------+------------------+--+
| col_name | data_type | comment |
+-----------+------------+------------------+--+
| id | int | new employee id |
| name | string | employee name |
+-----------+------------+------------------+--+
create table t1 as select * from another_table
desc t1 //excludes comments
+-----------+------------+----------+--+
| col_name | data_type | comment |
+-----------+------------+----------+--+
| id | int | |
| name | string | |
+-----------+------------+----------+--+
但有一个解决办法。创建视图时,可以指定带有注释的各个列
create view v2(id2 comment 'vemp id', name2 comment 'vemp name') as select * from another_table;
+-----------+------------+------------+--+
| col_name | data_type | comment |
+-----------+------------+------------+--+
| id2 | int | vemp id |
| name2 | string | vemp name |
+-----------+------------+------------+--+
我观察到的是,即使从另一个表创建表,注释也不会被继承。看起来这是默认行为
create table t1 like another_table
desc t1 //includes comments
+-----------+------------+------------------+--+
| col_name | data_type | comment |
+-----------+------------+------------------+--+
| id | int | new employee id |
| name | string | employee name |
+-----------+------------+------------------+--+
create table t1 as select * from another_table
desc t1 //excludes comments
+-----------+------------+----------+--+
| col_name | data_type | comment |
+-----------+------------+----------+--+
| id | int | |
| name | string | |
+-----------+------------+----------+--+
但有一个解决办法。创建视图时,可以指定带有注释的各个列
create view v2(id2 comment 'vemp id', name2 comment 'vemp name') as select * from another_table;
+-----------+------------+------------+--+
| col_name | data_type | comment |
+-----------+------------+------------+--+
| id2 | int | vemp id |
| name2 | string | vemp name |
+-----------+------------+------------+--+
你的继承权是对的。我不确定我是否理解原因,但正如你所说,我们可以利用你的伎俩。因为我有200条注释的表和10多个表,所以我在pyspark中自动使用了几行。谢谢你的继承权是正确的。我不确定我是否理解原因,但正如你所说,我们可以利用你的伎俩。因为我有200条注释的表和10多个表,所以我在pyspark中自动使用了几行。谢谢