swamirishi commented on code in PR #9317: URL: https://github.com/apache/ozone/pull/9317#discussion_r2551164787
########## hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/snapshot/util/TableMergeIterator.java: ########## @@ -0,0 +1,109 @@ +/* + * 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.hadoop.ozone.om.snapshot.util; + +import java.io.UncheckedIOException; +import java.util.ArrayList; +import java.util.Collections; +import java.util.Iterator; +import java.util.List; +import org.apache.hadoop.hdds.utils.IOUtils; +import org.apache.hadoop.hdds.utils.db.CodecException; +import org.apache.hadoop.hdds.utils.db.RocksDatabaseException; +import org.apache.hadoop.hdds.utils.db.Table; +import org.apache.hadoop.hdds.utils.db.Table.KeyValue; +import org.apache.hadoop.ozone.util.ClosableIterator; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * TableMergeIterator is an implementation of an iterator that merges multiple table iterators + * and filters the data based on the keys provided by another iterator. + * + * This iterator allows sequential traversal of all keys and their corresponding values + * across multiple tables. For each key, it gathers the associated value from each table. + * If a particular table does not have the entry for the given key, a null value is included in its place. + * + * This class is primarily designed to support efficient merging and filtering operations + * across multiple key-value tables. + * + * @param <K> The type of keys, which must be comparable. + * @param <V> The type of values. + */ +public class TableMergeIterator<K extends Comparable<K>, V> implements ClosableIterator<KeyValue<K, List<V>>> { + + private static final Logger LOG = LoggerFactory.getLogger(TableMergeIterator.class); + + private final Iterator<K> keysToFilter; + private final Table.KeyValueIterator<K, V>[] itrs; + private final List<KeyValue<K, V>> kvs; + private final List<V> nextValues; + + public TableMergeIterator(Iterator<K> keysToFilter, K prefix, Table<K, V>... tables) + throws RocksDatabaseException, CodecException { + this.itrs = new Table.KeyValueIterator[tables.length]; + for (int i = 0; i < tables.length; i++) { + this.itrs[i] = tables[i].iterator(prefix); + } + this.kvs = new ArrayList<>(Collections.nCopies(tables.length, null)); + this.nextValues = new ArrayList<>(Collections.nCopies(tables.length, null)); + this.keysToFilter = keysToFilter; + } + + @Override + public void close() { + IOUtils.close(LOG, itrs); + } + + @Override + public boolean hasNext() { + return keysToFilter.hasNext(); + } + + private V updateAndGetValueAtIndex(K key, int index) { + Table.KeyValueIterator<K, V> itr = itrs[index]; + if (itr.hasNext() && (kvs.get(index) == null || key.compareTo(kvs.get(index).getKey()) > 0)) { Review Comment: key can never be null. If it is null then it would fetch wrong results -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
