sunchao commented on a change in pull request #32082:
URL: https://github.com/apache/spark/pull/32082#discussion_r614231563
##########
File path:
sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/functions/ScalarFunction.java
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@@ -30,10 +30,71 @@
* <p>
* The JVM type of result values produced by this function must be the type
used by Spark's
* InternalRow API for the {@link DataType SQL data type} returned by {@link
#resultType()}.
+ * <p>
+ * <b>IMPORTANT</b>: the default implementation of {@link #produceResult}
throws
+ * {@link UnsupportedOperationException}. Users can choose to override this
method, or implement
+ * a "magic method" with name {@link #MAGIC_METHOD_NAME} which takes
individual parameters
+ * instead of a {@link InternalRow}. The magic method will be loaded by Spark
through Java
+ * reflection and also will provide better performance in general, due to
optimizations such as
+ * codegen, Java boxing and so on.
+ *
+ * For example, a scalar UDF for adding two integers can be defined as follow
with the magic
+ * method approach:
+ *
+ * <pre>
+ * public class IntegerAdd implements{@code ScalarFunction<Integer>} {
+ * public int invoke(int left, int right) {
+ * return left + right;
+ * }
+ *
+ * {@literal @}Override
+ * public produceResult(InternalRow input) {
Review comment:
Yes. I think I'll just remove it from the example then as it might cause
some confusion.
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