cloud-fan commented on a change in pull request #32407:
URL: https://github.com/apache/spark/pull/32407#discussion_r627928025
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File path:
sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/functions/ScalarFunction.java
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@@ -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.
- *
+ * {@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 stateless Java functions, 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.
Review comment:
hmm, how static method helps with the null check?
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