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https://issues.apache.org/jira/browse/FLINK-3599?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15473575#comment-15473575
 ] 

ASF GitHub Bot commented on FLINK-3599:
---------------------------------------

Github user ggevay commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2211#discussion_r77987122
  
    --- Diff: 
flink-core/src/main/java/org/apache/flink/api/java/typeutils/PojoTypeInfo.java 
---
    @@ -70,10 +77,41 @@
        private static final Pattern PATTERN_NESTED_FIELDS = 
Pattern.compile(REGEX_NESTED_FIELDS);
        private static final Pattern PATTERN_NESTED_FIELDS_WILDCARD = 
Pattern.compile(REGEX_NESTED_FIELDS_WILDCARD);
     
    +   private static final Map<Class<?>, Class<? extends TypeSerializer>> 
customSerializers = new HashMap<>();
    +   private static final Map<Tuple2<ArrayList<Integer>, Class>, Class<? 
extends TypeComparator>> customComparators =
    +           new HashMap<>();
    +
        private final PojoField[] fields;
        
        private final int totalFields;
     
    +   /**
    +    * Register a custom serializer for a type. The precedence of the 
serializers
    +    * is the following (highest to lowest): Kryo, Avro, Custom, Generated, 
Flink.
    +    * The chosen serializer will be the first one from the list that is 
turned on.
    +    *
    +    */
    +   public static <C, S extends TypeSerializer<C>> void 
registerCustomSerializer(Class<C> clazz, Class<S> ser) {
    +           Constructor<?>[] ctors = ser.getConstructors();
    +           assert ctors.length == 1;
    +           assert ctors[0].getParameterTypes().length == 0;
    +           customSerializers.put(clazz, ser);
    +   }
    +
    +   /**
    +    * Register a custom comparator for a type. The precedence of the 
serializers
    +    * is the following (highest to lowest): Custom, Generated, Flink.
    +    * The chosen serializer will be the first one from the list that is 
turned on.
    +    *
    +    */
    +   public static <S extends TypeComparator> void 
registerCustomComparator(ArrayList<Integer> keyIds,
    +                                                                           
                                                                        Class 
clazz, Class<S> comp) {
    +           Constructor<?>[] ctors = comp.getConstructors();
    +           assert ctors.length == 1;
    +           assert ctors[0].getParameterTypes().length == 0;
    --- End diff --
    
    Same problems as above.


> GSoC: Code Generation in Serializers
> ------------------------------------
>
>                 Key: FLINK-3599
>                 URL: https://issues.apache.org/jira/browse/FLINK-3599
>             Project: Flink
>          Issue Type: Improvement
>          Components: Type Serialization System
>            Reporter: Márton Balassi
>            Assignee: Gabor Horvath
>              Labels: gsoc2016, mentor
>
> The current implementation of the serializers can be a
> performance bottleneck in some scenarios. These performance problems were
> also reported on the mailing list recently [1].
> E.g. the PojoSerializer uses reflection for accessing the fields, which is 
> slow [2].
> For the complete proposal see [3].
> [1] 
> http://apache-flink-mailing-list-archive.1008284.n3.nabble.com/Tuple-performance-and-the-curious-JIT-compiler-td10666.html
> [2] 
> https://github.com/apache/flink/blob/master/flink-core/src/main/java/org/apache/flink/api/java/typeutils/runtime/PojoSerializer.java#L369
> [3] 
> https://docs.google.com/document/d/1VC8lCeErx9kI5lCMPiUn625PO0rxR-iKlVqtt3hkVnk



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