dongjoon-hyun commented on a change in pull request #32407:
URL: https://github.com/apache/spark/pull/32407#discussion_r627105752
##########
File path:
sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/functions/ScalarFunction.java
##########
@@ -29,33 +29,62 @@
* <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()}.
+ * The mapping between {@link DataType} and the corresponding JVM type is
defined below.
* <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 will also provide better performance in general, due to
optimizations such as
- * codegen, removal of Java boxing, etc.
- *
- * For example, a scalar UDF for adding two integers can be defined as follow
with the magic
+ * {@link UnsupportedOperationException}. Users must choose to either 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 approach is generally
recommended because it
+ * provides better performance over the default {@link #produceResult}, due to
optimizations such
+ * as whole-stage codegen, elimination of Java boxing, etc.
+ * <p>
+ * In addition, for functions implemented in Java that are stateless, users
can optionally define
+ * the {@link #MAGIC_METHOD_NAME} as a static method, which further avoids
certain runtime costs
+ * such as nullness check on the method receiver, potential Java dynamic
dispatch, etc.
+ * <p>
+ * For example, a scalar UDF for adding two integers can be defined as follow
with the static magic
* method approach:
*
* <pre>
* public class IntegerAdd implements{@code ScalarFunction<Integer>} {
+ * public DataType[] inputTypes() {
+ * return new DataType[] { DataTypes.IntegerType, DataTypes.IntegerType
};
+ * }
* public int invoke(int left, int right) {
Review comment:
This is not a static method which is inconsistent with line 45, `the
static magic method approach`. I guess one of them should be changed for
consistency.
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