### What changes were proposed in this pull request? Previously, user can issue `SHOW TABLES` to get info of both tables and views. This PR (SPARK-31113) implements `SHOW VIEWS` SQL command similar to HIVE to get views only.(https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL#LanguageManualDDL-ShowViews) **Hive** -- Only show view names ``` hive> SHOW VIEWS; OK view_1 view_2 ... ``` **Spark(Hive-Compatible)** -- Only show view names, used in tests and `SparkSQLDriver` for CLI applications ``` SHOW VIEWS IN showdb; view_1 view_2 ... ``` **Spark** -- Show more information database/viewName/isTemporary ``` spark-sql> SHOW VIEWS; userdb view_1 false userdb view_2 false ... ``` ### Why are the changes needed? `SHOW VIEWS` command provides better granularity to only get information of views. ### Does this PR introduce any user-facing change? Add new `SHOW VIEWS` SQL command ### How was this patch tested? Add new test `show-views.sql` and pass existing tests Closes #27897 from Eric5553/ShowViews. Authored-by: Eric Wu <492960551@qq.com> Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>
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layout | title | displayTitle | license |
---|---|---|---|
global | ALTER VIEW | ALTER VIEW | Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. |
Description
The ALTER VIEW
statement can alter metadata associated with the view. It can change the definition of the view, change
the name of a view to a different name, set and unset the metadata of the view by setting TBLPROPERTIES
.
RENAME View
Renames the existing view. If the new view name already exists in the source database, a TableAlreadyExistsException
is thrown. This operation
does not support moving the views across databases.
Syntax
{% highlight sql %} ALTER VIEW view_identifier RENAME TO view_identifier {% endhighlight %}
Parameters
view_identifier
-
Specifies a view name, which may be optionally qualified with a database name.
Syntax:[ database_name. ] view_name
SET View Properties
Set one or more properties of an existing view. The properties are the key value pairs. If the properties' keys exist, the values are replaced with the new values. If the properties' keys do not exist, the key value pairs are added into the properties.
Syntax
{% highlight sql %} ALTER VIEW view_identifier SET TBLPROPERTIES ( property_key = property_val [ , ... ] ) {% endhighlight %}
Parameters
view_identifier
-
Specifies a view name, which may be optionally qualified with a database name.
Syntax:[ database_name. ] view_name
property_key
-
Specifies the property key. The key may consists of multiple parts separated by dot.
Syntax:[ key_part1 ] [ .key_part2 ] [ ... ]
UNSET View Properties
Drop one or more properties of an existing view. If the specified keys do not exist, an exception is thrown. Use
IF EXISTS
to avoid the exception.
Syntax
{% highlight sql %} ALTER VIEW view_identifier UNSET TBLPROPERTIES [ IF EXISTS ] ( property_key [ , ... ] ) {% endhighlight %}
Parameters
view_identifier
-
Specifies a view name, which may be optionally qualified with a database name.
Syntax:[ database_name. ] view_name
property_key
-
Specifies the property key. The key may consists of multiple parts separated by dot.
Syntax:[ key_part1 ] [ .key_part2 ] [ ... ]
ALTER View AS SELECT
ALTER VIEW view_identifier AS SELECT
statement changes the definition of a view, the SELECT
statement must be valid,
and the view_identifier
must exist.
Syntax
{% highlight sql %} ALTER VIEW view_identifier AS select_statement {% endhighlight %}
Parameters
view_identifier
-
Specifies a view name, which may be optionally qualified with a database name.
Syntax:[ database_name. ] view_name
select_statement
- Specifies the definition of the view, detail check select_statement
Examples
{% highlight sql %}
-- Rename only changes the view name.
-- The source and target databases of the view have to be the same.
-- Use qualified or unqualified name for the source and target view
ALTER VIEW tempdb1.v1 RENAME TO tempdb1.v2;
-- Verify that the new view is created. DESCRIBE TABLE EXTENDED tempdb1.v2;
+----------------------------+----------+-------+ |col_name |data_type |comment| +----------------------------+----------+-------+ |c1 |int |null | |c2 |string |null | | | | | |# Detailed Table Information| | | |Database |tempdb1 | | |Table |v2 | | +----------------------------+----------+-------+
-- Before ALTER VIEW SET TBLPROPERTIES DESC TABLE EXTENDED tempdb1.v2;
+----------------------------+----------+-------+ |col_name |data_type |comment| +----------------------------+----------+-------+ |c1 |int |null | |c2 |string |null | | | | | |# Detailed Table Information| | | |Database |tempdb1 | | |Table |v2 | | |Table Properties |[....] | | +----------------------------+----------+-------+
-- Set properties in TBLPROPERTIES ALTER VIEW tempdb1.v2 SET TBLPROPERTIES ('created.by.user' = "John", 'created.date' = '01-01-2001' );
-- Use DESCRIBE TABLE EXTENDED tempdb1.v2
to verify
DESC TABLE EXTENDED tempdb1.v2;
+----------------------------+-----------------------------------------------------+-------+ |col_name |data_type |comment| +----------------------------+-----------------------------------------------------+-------+ |c1 |int |null | |c2 |string |null | | | | | |# Detailed Table Information| | | |Database |tempdb1 | | |Table |v2 | | |Table Properties |[created.by.user=John, created.date=01-01-2001, ....]| | +----------------------------+-----------------------------------------------------+-------+
-- Remove the key created.by.user
and created.date
from TBLPROPERTIES
ALTER VIEW tempdb1.v2 UNSET TBLPROPERTIES ('created.by.user', 'created.date');
--Use DESC TABLE EXTENDED tempdb1.v2
to verify the changes
DESC TABLE EXTENDED tempdb1.v2;
+----------------------------+----------+-------+ |col_name |data_type |comment| +----------------------------+----------+-------+ |c1 |int |null | |c2 |string |null | | | | | |# Detailed Table Information| | | |Database |tempdb1 | | |Table |v2 | | |Table Properties |[....] | | +----------------------------+----------+-------+
-- Change the view definition ALTER VIEW tempdb1.v2 AS SELECT * FROM tempdb1.v1;
-- Use DESC TABLE EXTENDED
to verify
DESC TABLE EXTENDED tempdb1.v2;
+----------------------------+---------------------------+-------+ |col_name |data_type |comment| +----------------------------+---------------------------+-------+ |c1 |int |null | |c2 |string |null | | | | | |# Detailed Table Information| | | |Database |tempdb1 | | |Table |v2 | | |Type |VIEW | | |View Text |select * from tempdb1.v1 | | |View Original Text |select * from tempdb1.v1 | | +----------------------------+---------------------------+-------+ {% endhighlight %}
Related Statements
Note:
ALTER VIEW
statement does not support SET SERDE
or SET SERDEPROPERTIES
properties