関数の記述 (SQL Analytics)DESCRIBE FUNCTION (SQL Analytics)

既存の関数の基本的なメタデータ情報を返します。Returns the basic metadata information of an existing function. メタデータ情報には、関数名、実装クラス、および使用状況の詳細が含まれます。The metadata information includes the function name, implementing class and the usage details. オプションを指定した場合は、 EXTENDED 拡張された使用状況情報と共に基本的なメタデータ情報が返されます。If the optional EXTENDED option is specified, the basic metadata information is returned along with the extended usage information.

構文Syntax

{ DESC | DESCRIBE } FUNCTION [ EXTENDED ] function_name

パラメーターParameters

  • function_namefunction_name

    システム内の既存の関数の名前。The name of an existing function in the system. 必要に応じて、関数名をデータベース名で修飾することもできます。The function name may be optionally qualified with a database name. がデータベースで修飾されている場合、 function_name 関数はユーザーが指定したデータベースから解決されます。それ以外の場合は、現在のデータベースから解決されます。If function_name is qualified with a database then the function is resolved from the user specified database, otherwise it is resolved from the current database.

    構文:[database_name.] function_nameSyntax: [database_name.] function_name

Examples

-- Describe a builtin scalar function.
-- Returns function name, implementing class and usage
DESC FUNCTION abs;
+-------------------------------------------------------------------+
|function_desc                                                      |
+-------------------------------------------------------------------+
|Function: abs                                                      |
|Class: org.apache.spark.sql.catalyst.expressions.Abs               |
|Usage: abs(expr) - Returns the absolute value of the numeric value.|
+-------------------------------------------------------------------+

-- Describe a builtin scalar function.
-- Returns function name, implementing class and usage and examples.
DESC FUNCTION EXTENDED abs;
+-------------------------------------------------------------------+
|function_desc                                                      |
+-------------------------------------------------------------------+
|Function: abs                                                      |
|Class: org.apache.spark.sql.catalyst.expressions.Abs               |
|Usage: abs(expr) - Returns the absolute value of the numeric value.|
|Extended Usage:                                                    |
|    Examples:                                                      |
|      > SELECT abs(-1);                                            |
|       1                                                           |
|                                                                   |
+-------------------------------------------------------------------+

-- Describe a builtin aggregate function
DESC FUNCTION max;
+--------------------------------------------------------------+
|function_desc                                                 |
+--------------------------------------------------------------+
|Function: max                                                 |
|Class: org.apache.spark.sql.catalyst.expressions.aggregate.Max|
|Usage: max(expr) - Returns the maximum value of `expr`.       |
+--------------------------------------------------------------+

-- Describe a builtin user defined aggregate function
-- Returns function name, implementing class and usage and examples.
DESC FUNCTION EXTENDED explode
+---------------------------------------------------------------+
|function_desc                                                  |
+---------------------------------------------------------------+
|Function: explode                                              |
|Class: org.apache.spark.sql.catalyst.expressions.Explode       |
|Usage: explode(expr) - Separates the elements of array `expr`  |
| into multiple rows, or the elements of map `expr` into        |
| multiple rows and columns. Unless specified otherwise, uses   |
| the default column name `col` for elements of the array or    |
| `key` and `value` for the elements of the map.                |
|Extended Usage:                                                |
|    Examples:                                                  |
|      > SELECT explode(array(10, 20));                         |
|       10                                                      |
|       20                                                      |
+---------------------------------------------------------------+