[GitHub] flink pull request #4331: [FLINK-7169][CEP] Support AFTER MATCH SKIP functio...

[dawidwys <gi...@git.apache.org>]

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

    https://github.com/apache/flink/pull/4331#discussion_r132132564
  
    --- Diff: flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/AfterMatchSkipStrategy.java ---
    @@ -0,0 +1,276 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +
    +package org.apache.flink.cep.nfa;
    +
    +import org.apache.flink.api.common.typeutils.CompatibilityResult;
    +import org.apache.flink.api.common.typeutils.CompatibilityUtil;
    +import org.apache.flink.api.common.typeutils.CompositeTypeSerializerConfigSnapshot;
    +import org.apache.flink.api.common.typeutils.TypeDeserializerAdapter;
    +import org.apache.flink.api.common.typeutils.TypeSerializer;
    +import org.apache.flink.api.common.typeutils.TypeSerializerConfigSnapshot;
    +import org.apache.flink.api.common.typeutils.UnloadableDummyTypeSerializer;
    +import org.apache.flink.api.java.tuple.Tuple2;
    +import org.apache.flink.core.memory.DataInputView;
    +import org.apache.flink.core.memory.DataInputViewStreamWrapper;
    +import org.apache.flink.core.memory.DataOutputView;
    +import org.apache.flink.core.memory.DataOutputViewStreamWrapper;
    +
    +import java.io.ByteArrayInputStream;
    +import java.io.ByteArrayOutputStream;
    +import java.io.IOException;
    +import java.io.ObjectInputStream;
    +import java.io.ObjectOutputStream;
    +import java.io.Serializable;
    +import java.util.List;
    +
    +
    +/**
    + * Indicate the skip strategy after a match process.
    + * <p>There're four kinds of strategies:
    + * SKIP_PAST_LAST_EVENT,
    + * SKIP_TO_NEXT_EVENT,
    + * SKIP_TO_FIRST_<code>PATTERN</code> and
    + * SKIP_TO_LAST_<code>PATTERN</code>
    + * </p>
    + */
    +public class AfterMatchSkipStrategy implements Serializable {
    +
    +	// default strategy
    +	SkipStrategy strategy = SkipStrategy.SKIP_TO_NEXT_EVENT;
    +
    +	// fields
    +	String patternName = null;
    +
    +	public AfterMatchSkipStrategy(){
    +		this(SkipStrategy.SKIP_TO_NEXT_EVENT, null);
    +	}
    +
    +	public AfterMatchSkipStrategy(SkipStrategy strategy) {
    +		this(strategy, null);
    +	}
    +
    +	public AfterMatchSkipStrategy(SkipStrategy strategy, String patternName) {
    --- End diff --
    
    I would change ctor's into factory methods. I think that way the requirements for `patternName` will be more visible and the the code would be less bloated.
    
    I have sth like this in mind:
    
    	public static AfterMatchSkipStrategy skipToFirst(String patternName) {
    		return new AfterMatchSkipStrategy(SkipStrategy.SKIP_TO_FIRST, patternName);
    	}
    
    	public static AfterMatchSkipStrategy skipToLast(String patternName) {
    		return new AfterMatchSkipStrategy(SkipStrategy.SKIP_TO_LAST, patternName);
    	}
    
    	public static AfterMatchSkipStrategy skipPastLastEvent() {
    		return new AfterMatchSkipStrategy(SkipStrategy.SKIP_PAST_LAST_EVENT);
    	}
    
    	public static AfterMatchSkipStrategy skipToNextEvent() {
    		return new AfterMatchSkipStrategy(SkipStrategy.SKIP_TO_NEXT_EVENT);
    	}
    
    Then the usage will be:
    
        AfterMatchSkipStrategy.skipToLast("end")
    
    instead of:
    
        new AfterMatchSkipStrategy(AfterMatchSkipStrategy.SkipStrategy.SKIP_TO_LAST, "end")



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