[GitHub] [flink] slinkydeveloper commented on a change in pull request #18352: [FLINK-15585][table] Improve function identifier string in plan digest

[GitBox <gi...@apache.org>]

slinkydeveloper commented on a change in pull request #18352:
URL: https://github.com/apache/flink/pull/18352#discussion_r784104335



##########
File path: flink-table/flink-table-common/src/main/java/org/apache/flink/table/functions/UserDefinedFunctionHelper.java
##########
@@ -243,6 +244,36 @@ public static void prepareInstance(ReadableConfig config, UserDefinedFunction fu
         cleanFunction(config, function);
     }
 
+    /**
+     * Returns whether a {@link UserDefinedFunction} can be easily serialized and identified by only
+     * a fully qualified class name. It must have a default constructor and no serializable fields.
+     */
+    public static boolean isClassNameSerializable(UserDefinedFunction function) {
+        final Class<?> functionClass = function.getClass();
+        if (!InstantiationUtil.hasPublicNullaryConstructor(functionClass)) {
+            // function must be parameterized
+            return false;
+        }
+        Class<?> currentClass = functionClass;
+        while (!currentClass.equals(UserDefinedFunction.class)) {
+            for (Field field : currentClass.getDeclaredFields()) {
+                if (!Modifier.isTransient(field.getModifiers())
+                        && !Modifier.isStatic(field.getModifiers())) {
+                    // function seems to be stateful
+                    return false;
+                }
+            }
+            currentClass = currentClass.getSuperclass();
+        }

Review comment:
       That sounds like a very magic way to find out whether a function is stateful or not. Don't we have a marker interface for that?

##########
File path: flink-table/flink-table-common/src/test/java/org/apache/flink/table/functions/UserDefinedFunctionHelperTest.java
##########
@@ -143,34 +162,27 @@ private void testErrorMessage() {
 
         @Nullable String expectedErrorMessage;
 
-        TestSpec(Class<? extends UserDefinedFunction> functionClass) {
+        TestSpec(
+                @Nullable Class<? extends UserDefinedFunction> functionClass,
+                @Nullable UserDefinedFunction functionInstance,
+                @Nullable CatalogFunction catalogFunction) {
             this.functionClass = functionClass;
-            this.functionInstance = null;
-            this.catalogFunction = null;
-        }
-
-        TestSpec(UserDefinedFunction functionInstance) {
-            this.functionClass = null;
             this.functionInstance = functionInstance;
-            this.catalogFunction = null;
-        }
-
-        TestSpec(CatalogFunction catalogFunction) {
-            this.functionClass = null;
-            this.functionInstance = null;
             this.catalogFunction = catalogFunction;
         }
 
         static TestSpec forClass(Class<? extends UserDefinedFunction> function) {
-            return new TestSpec(function);
+            return new TestSpec(function, null, null);
         }
 
         static TestSpec forInstance(UserDefinedFunction function) {
-            return new TestSpec(function);
+            return new TestSpec(null, function, null);
         }
 
-        static TestSpec forCatalogFunction(String className, FunctionLanguage language) {
-            return new TestSpec(new CatalogFunctionMock(className, language));
+        static TestSpec forCatalogFunction(
+                String className,
+                @SuppressWarnings("SameParameterValue") FunctionLanguage language) {

Review comment:
       What warning is this one?

##########
File path: flink-table/flink-table-common/src/main/java/org/apache/flink/table/functions/UserDefinedFunction.java
##########
@@ -58,9 +60,13 @@
 
     /** Returns a unique, serialized representation for this function. */
     public final String functionIdentifier() {
+        final String className = getClass().getName();
+        if (isClassNameSerializable(this)) {
+            return className;
+        }
         final String md5 =
                 EncodingUtils.hex(EncodingUtils.md5(EncodingUtils.encodeObjectToString(this)));
-        return getClass().getName().replace('.', '$').concat("$").concat(md5);
+        return className.concat("$").concat(md5);

Review comment:
       Does this logic works when the function is implemented as a scala `object`?




-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: issues-unsubscribe@flink.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org