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From fhueske <...@git.apache.org>
Subject [GitHub] incubator-flink pull request: providing accumulator example as pro...
Date Wed, 02 Jul 2014 09:40:09 GMT
Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/incubator-flink/pull/55#discussion_r14448525
  
    --- Diff: stratosphere-examples/stratosphere-java-examples/src/main/java/eu/stratosphere/example/java/relational/FilterAndCountIncompleteLines.java
---
    @@ -0,0 +1,248 @@
    +/***********************************************************************************************************************
    + *
    + * Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
    + *
    + * Licensed 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 eu.stratosphere.example.java.relational;
    +
    +import java.io.DataInput;
    +import java.io.DataOutput;
    +import java.io.IOException;
    +import java.util.ArrayList;
    +import java.util.Collection;
    +import java.util.List;
    +
    +import eu.stratosphere.api.common.JobExecutionResult;
    +import eu.stratosphere.api.common.accumulators.Accumulator;
    +import eu.stratosphere.api.java.DataSet;
    +import eu.stratosphere.api.java.ExecutionEnvironment;
    +import eu.stratosphere.api.java.functions.FilterFunction;
    +import eu.stratosphere.api.java.tuple.Tuple;
    +import eu.stratosphere.api.java.tuple.Tuple3;
    +import eu.stratosphere.configuration.Configuration;
    +
    +/**
    + * This program filters lines from a CSV file with empty fields. In doing so, it counts
the number of empty fields per
    + * column within a CSV file using a custom accumulator for vectors. In this context,
empty fields are those, that at
    + * most contain whitespace characters like space and tab.
    + * <p>
    + * The input file is a plain text CSV file with the semicolon as field separator and
double quotes as field delimiters
    + * and three columns. See {@link #getDataSet(ExecutionEnvironment)} for configuration.
    + * <p>
    + * Usage: <code>FilterAndCountIncompleteLines [&lt;input file path&gt;
[&lt;result path&gt;]]</code> <br>
    + * <p>
    + * This example shows how to use:
    + * <ul>
    + * <li>custom accumulators
    + * <li>tuple data types
    + * <li>inline-defined functions
    + * </ul>
    + */
    +@SuppressWarnings("serial")
    +public class FilterAndCountIncompleteLines {
    +
    +	// *************************************************************************
    +	// PROGRAM
    +	// *************************************************************************
    +
    +	private static final String EMPTY_FIELD_ACCUMULATOR = "empty-fields";
    +
    +	public static void main(final String[] args) throws Exception {
    +
    +		if (!parseParameters(args)) {
    +			return;
    +		}
    +
    +		final ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
    +
    +		// get the data set
    +		final DataSet<Tuple> file = getDataSet(env);
    +
    +		// filter lines with empty fields
    +		final DataSet<Tuple> filteredLines = file.filter(new FilterFunction<Tuple>()
{
    --- End diff --
    
    Would you mind not defining the FilterFunction inline. 
    IMO, separating the data flow and the UDF logic is easier to read, esp. if the UDF implements
multiple methods.


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