com.bakdata.dedupe.deduplication.Deduplication Maven / Gradle / Ivy
Show all versions of core Show documentation
/*
* MIT License
*
* Copyright (c) 2019 bakdata GmbH
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package com.bakdata.dedupe.deduplication;
import com.bakdata.util.StreamUtil;
import java.util.Collection;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import lombok.NonNull;
/**
* A full deduplication process, which ensures that no duplicate record is emitted.
* In general, all implementations will ensure that the user receives a duplicate-free datasets, either through
* repeated updates or by providing a duplicate-free dataset.
* The actual implementation may use any means necessary to find duplicates, to ensure proper transitivity ((A,B) is
* duplicate and (B,C) is duplicate implies that (A,C) is duplicate), and to give a resulting representation.
*
* @param the type of the record
*/
@FunctionalInterface
public interface Deduplication {
/**
* Deduplicates the dataset.
* Note that for online algorithms, duplicates will be repeatedly emitted with updated
* representation, since it is impossible to suppress earlier emission without blocking execution. The user needs to
* invalidate earlier results through external means (for example, putting them in a key-value store with the key
* being the id of the duplicate).
*
* @param records the record that should be freed from duplicates.
* @return a duplicate-free dataset with the above mentioned limitation for online algorithms.
*/
@NonNull Stream deduplicate(@NonNull Stream records);
/**
* Deduplicates the dataset.
* For online algorithms this method can only be applied on a finite stream and could be used to verify results
* in a test or compare performance to an offline algorithm.
* For online algorithms, this method may emit duplicates repeatedly with the same id, since an online algorithm
* usually eagerly emits results. To ensure a real duplicate-free dataset, use {@link
* #materializedDeduplicate(Iterable, Function)}.
*
* @param records the record that should be freed from duplicates.
* @return a duplicate-free dataset with the above mentioned limitation for online algorithms.
* @implSpec For online algorithms, it is strongly encouraged that duplicates are filtered such that only the final
* representation remains.
*/
default @NonNull Collection materializedDeduplicate(final @NonNull Iterable records) {
return this.deduplicate(StreamUtil.stream(records)).collect(Collectors.toList());
}
/**
* Selects the candidates for the given records and materializes them. The additional idExtractor ensures that
* previously found duplicates are removed from the output.
* For online algorithms this method can only be applied on a finite stream and could be used to verify results
* in a test or compare performance to an offline algorithm.
*
* @param records the record that should be freed from duplicates.
* @return a duplicate-free dataset.
* @implSpec For online algorithms, it is strongly encouraged that duplicates are filtered such that only the final
* representation remains.
*/
default @NonNull Collection materializedDeduplicate(final @NonNull Iterable records,
final @NonNull Function idExtractor) {
return this.deduplicate(StreamUtil.stream(records))
.collect(Collectors.toMap(idExtractor, Function.identity()))
.values();
}
}