org.apache.parquet.hadoop.metadata.ConcatenatingKeyValueMetadataMergeStrategy Maven / Gradle / Ivy
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* 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.parquet.hadoop.metadata;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;
/**
* Strategy to concatenate if there are multiple values for a given key in metadata.
* Note: use this with caution. This is expected to work only for certain use cases.
*/
public class ConcatenatingKeyValueMetadataMergeStrategy implements KeyValueMetadataMergeStrategy {
private static final String DEFAULT_DELIMITER = ",";
private final String delimiter;
/**
* Default constructor.
*/
public ConcatenatingKeyValueMetadataMergeStrategy() {
this.delimiter = DEFAULT_DELIMITER;
}
/**
* Constructor to use different delimiter for concatenation.
*
* @param delim delimiter char sequence.
*/
public ConcatenatingKeyValueMetadataMergeStrategy(String delim) {
this.delimiter = delim;
}
/**
* @param keyValueMetaData the merged app specific metadata
*/
public Map merge(Map> keyValueMetaData) {
Map mergedKeyValues = new HashMap();
for (Map.Entry> entry : keyValueMetaData.entrySet()) {
mergedKeyValues.put(entry.getKey(), entry.getValue().stream().collect(Collectors.joining(this.delimiter)));
}
return mergedKeyValues;
}
}