Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/18749#discussion_r130223158
--- Diff:
sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/ExpressionDescription.java
---
@@ -24,20 +24,50 @@
/**
* ::DeveloperApi::
-
+ *
* A function description type which can be recognized by
FunctionRegistry, and will be used to
* show the usage of the function in human language.
*
* `usage()` will be used for the function usage in brief way.
- * `extended()` will be used for the function usage in verbose way, suppose
- * an example will be provided.
*
- * And we can refer the function name by `_FUNC_`, in `usage` and
`extended`, as it's
+ * These below are concatenated and used for the function usage in verbose
way, suppose arguments,
+ * examples, note and since will be provided.
+ *
+ * `arguments()` describes arguments for the expression. This should
follow the format as below:
+ *
+ * Arguments:
+ * * arg0 - ...
+ * ....
+ * * arg1 - ...
+ * ....
+ *
+ * `examples()` describes examples for the expression. This should follow
the format as below:
+ *
+ * Examples:
+ * > SELECT ...;
+ * ...
+ * > SELECT ...;
+ * ...
+ *
+ * `note()` contains some notes for the expression optionally.
+ *
+ * `since()` contains version information for the expression. Version is
specified by,
+ * for example, "2.2.0".
+ *
+ * We can refer the function name by `_FUNC_`, in `usage`, `arguments`
and `examples`, as it's
* registered in `FunctionRegistry`.
+ *
+ * Note that, if `extended()` is defined, `arguments()`, `examples()`,
`note()` and `since()` will
+ * be ignored and `extended()` will be used for the extended description
for backward
+ * compatibility.
*/
@DeveloperApi
@Retention(RetentionPolicy.RUNTIME)
public @interface ExpressionDescription {
- String usage() default "_FUNC_ is undocumented";
- String extended() default "\n No example/argument for _FUNC_.\n";
+ String usage() default "";
+ String extended() default "";
--- End diff --
In the last commit
https://github.com/apache/spark/pull/18749/commits/bf48875057ca5978b88cacab455292b64daf1557,
I tried to keep the original behaviour and compatibility (although I guess we
are fine to break this as said in few comments above):
For `ExpressionDescription` and `ExpressionInfo`,
if `extended` is an empty string (the default value), it creates the
`extended` made by `arguments`, `examples`, `note` and `since` and use this as
the extended description.
if `extended` is a non-empty string, it ignores the new `arguments`,
`examples`, `note` and `since` but use this as the extended description,
assuming this was set manually.
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