srowen commented on a change in pull request #25553: [SPARK-28797][DOC]
Document DROP FUNCTION statement in SQL Reference.
URL: https://github.com/apache/spark/pull/25553#discussion_r332503425
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File path: docs/sql-ref-syntax-ddl-drop-function.md
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@@ -19,4 +19,87 @@ license: |
limitations under the License.
---
-**This page is under construction**
+### Description
+The `DROP FUNCTION` statement drops a temporary or user defined function
(UDF). An exception will
+ be thrown if the function does not exist.
+
+### Syntax
+{% highlight sql %}
+DROP [TEMPORARY] FUNCTION [IF EXISTS] [db_name.]function_name;
+{% endhighlight %}
+
+
+### Parameters
+
+<dl>
+ <dt><code><em>function_name</em></code></dt>
+ <dd>The name of an existing function.</dd>
+</dl>
+
+<dl>
+ <dt><code><em>TEMPORARY</em></code></dt>
+ <dd>Should be used to delete the `temporary` function.</dd>
+</dl>
+
+<dl>
+ <dt><code><em>IF EXISTS</em></code></dt>
+ <dd>If specified, no exception is thrown when the function does not
exist.</dd>
+</dl>
+
+### Example
+{% highlight sql %}
+-- Create a permanent function `test_avg`
+CREATE FUNCTION test_avg as
'org.apache.hadoop.hive.ql.udf.generic.GenericUDAFAverage';
+
+-- List user functions
+SHOW USER FUNCTIONS;
+ +-------------------+
+ | function |
+ +-------------------+
+ | default.test_avg |
+ +-------------------+
+
+-- Create Temporary function `test_avg`
+CREATE TEMPORARY FUNCTION test_avg as
'org.apache.hadoop.hive.ql.udf.generic.GenericUDAFAverage';
+
+-- List user functions
+SHOW USER FUNCTIONS;
+ +-------------------+
+ | function |
+ +-------------------+
+ | default.test_avg |
+ | test_avg |
+ +-------------------+
+
+-- Drop Permanent function
+DROP FUNCTION test_avg;
+ +---------+
+ | Result |
+ +---------+
+ +---------+
+
+-- Try to drop Permanent function which is not present
+DROP FUNCTION test_avg;
+ Error: Error running query:
+ org.apache.spark.sql.catalyst.analysis.NoSuchPermanentFunctionException:
+ Function 'default.test_avg' not found in database 'default'; (state=,code=0)
+
+-- List the functions after dropping, it should list only temporary function
+SHOW USER FUNCTIONS;
+ +-----------+
+ | function |
+ +-----------+
+ | temp_avg |
Review comment:
Ping @sandeep-katta to fix that part
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