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From hornn <...@git.apache.org>
Subject [GitHub] incubator-hawq pull request: HAWQ-178: Add JSON plugin support in ...
Date Tue, 02 Feb 2016 01:47:25 GMT
Github user hornn commented on a diff in the pull request:

    https://github.com/apache/incubator-hawq/pull/302#discussion_r51511168
  
    --- Diff: pxf/pxf-json/src/main/java/org/apache/hawq/pxf/plugins/json/JsonRecordReader.java
---
    @@ -0,0 +1,166 @@
    +package org.apache.hawq.pxf.plugins.json;
    +
    +/*
    + * 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.
    + */
    +
    +import static org.apache.commons.lang3.StringUtils.isEmpty;
    +
    +import java.io.BufferedInputStream;
    +import java.io.IOException;
    +import java.security.InvalidParameterException;
    +
    +import org.apache.commons.logging.Log;
    +import org.apache.commons.logging.LogFactory;
    +import org.apache.hadoop.fs.FSDataInputStream;
    +import org.apache.hadoop.fs.FileSystem;
    +import org.apache.hadoop.fs.Path;
    +import org.apache.hadoop.io.LongWritable;
    +import org.apache.hadoop.io.Text;
    +import org.apache.hadoop.mapred.FileSplit;
    +import org.apache.hadoop.mapred.JobConf;
    +import org.apache.hadoop.mapred.RecordReader;
    +import org.apache.hawq.pxf.api.Fragment;
    +
    +/**
    + * {@link RecordReader} implementation that can read multiline JSON objects.
    + */
    +public class JsonRecordReader implements RecordReader<LongWritable, Text> {
    +
    +	private static final Log LOG = LogFactory.getLog(JsonRecordReader.class);
    +
    +	public static final String RECORD_IDENTIFIER = "json.input.format.record.identifier";
    +
    +	private JsonStreamReader streamReader = null;
    +	private long start = 0, end = 0;
    +	private float toRead = 0;
    +	private String identifier = null;
    +
    +	/**
    +	 * @param conf
    +	 *            Hadoop context
    +	 * @param split
    +	 *            HDFS Split as defined by the {@link Fragment}.
    +	 * @throws IOException
    +	 */
    +	public JsonRecordReader(JobConf conf, FileSplit split) throws IOException {
    +		LOG.debug("JsonRecordReader constructor called.  Conf is " + conf + ". Split is " +
split);
    +		this.identifier = conf.get(RECORD_IDENTIFIER);
    +		LOG.debug("Identifier is " + this.identifier);
    +
    +		if (isEmpty(this.identifier)) {
    +			throw new InvalidParameterException(RECORD_IDENTIFIER + " is not set.");
    +		} else {
    +			LOG.debug("Initializing JsonRecordReader with identifier " + identifier);
    +		}
    +
    +		// get relevant data
    +		Path file = split.getPath();
    +
    +		LOG.debug("File is " + file);
    +
    +		start = split.getStart();
    +		end = start + split.getLength();
    +		toRead = end - start;
    +		LOG.debug("FileSystem is " + FileSystem.get(conf));
    +
    +		FSDataInputStream strm = FileSystem.get(conf).open(file);
    +
    +		LOG.debug("Retrieved file stream ");
    +
    +		if (start != 0) {
    +			strm.seek(start);
    +		}
    +
    +		streamReader = new JsonStreamReader(identifier, new BufferedInputStream(strm));
    +
    +		LOG.debug("Reader is " + streamReader);
    +	}
    +
    +	/*
    +	 * {@inheritDoc}
    +	 */
    +	@Override
    +	public boolean next(LongWritable key, Text value) throws IOException {
    +
    +		boolean retval = false;
    +		boolean keepGoing = false;
    +		do {
    +			// Exit condition (end of block/file)
    +			if (streamReader.getBytesRead() >= (end - start)) {
    +				return false;
    +			}
    +
    +			keepGoing = false;
    +			String record = streamReader.getJsonRecord();
    +			if (record != null) {
    +				if (JsonUtil.decodeLineToJsonNode(record) == null) {
    --- End diff --
    
    We call decodeLineToJsonNode twice for each record - one time here (accessing), and one
time in the resolver. I don't know if it is a heavy operation or not, but it is slow because
this function is synchronized, so multiple requests will be queued.
    Consider removing this logic here - and failing in the resolver. We also have a notion
of BadRecordException that can be used when there is a malformatted record. 


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