/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License, Version 1.0 only
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* (the "License"). You may not use this file except in compliance
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* with the License.
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*
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* You can obtain a copy of the license at legal-notices/CDDLv1_0.txt
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* or http://forgerock.org/license/CDDLv1.0.html.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at legal-notices/CDDLv1_0.txt.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information:
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* Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*
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*
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* Copyright 2014 ForgeRock AS.
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*/
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package org.opends.server.replication.server.changelog.file;
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import static org.opends.server.replication.server.changelog.api.DBCursor.KeyMatchingStrategy.*;
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import static org.opends.server.replication.server.changelog.api.DBCursor.PositionStrategy.*;
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import org.opends.server.replication.common.CSN;
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import org.opends.server.replication.protocol.UpdateMsg;
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import org.opends.server.replication.server.changelog.api.ChangelogException;
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import org.opends.server.replication.server.changelog.api.DBCursor;
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import org.opends.server.replication.server.changelog.file.Log.RepositionableCursor;
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/**
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* A cursor on ReplicaDB, which can re-initialize itself after exhaustion.
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* <p>
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* The cursor provides a java.sql.ResultSet like API :
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* <pre>
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* FileReplicaDBCursor cursor = ...;
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* try {
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* while (cursor.next()) {
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* Record record = cursor.getRecord();
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* // ... can call cursor.getRecord() again: it will return the same result
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* }
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* }
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* finally {
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* close(cursor);
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* }
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* }
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* </pre>
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* <p>
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* The cursor automatically re-initializes itself if it is exhausted: if a
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* record is newly available, a subsequent call to the {@code next()} method will
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* return {@code true} and the record will be available by calling {@code getRecord()}
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* method.
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*
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* \@NotThreadSafe
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*/
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class FileReplicaDBCursor implements DBCursor<UpdateMsg>
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{
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/** The underlying cursor. */
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private final RepositionableCursor<CSN, UpdateMsg> cursor;
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/** The next record to return. */
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private Record<CSN, UpdateMsg> nextRecord;
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/** The CSN to re-start with in case the cursor is exhausted. */
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private CSN lastNonNullCurrentCSN;
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private PositionStrategy positionStrategy;
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/**
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* Creates the cursor from provided log cursor and start CSN.
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*
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* @param cursor
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* The underlying log cursor to read log.
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* @param startCSN
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* The CSN to use as a start point (excluded from cursor, the lowest
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* CSN higher than this CSN is used as the real start point).
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* @param positionStrategy
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* Cursor position strategy, which allow to choose if cursor must
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* start from the provided CSN or just after the provided CSN.
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*/
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FileReplicaDBCursor(
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final RepositionableCursor<CSN, UpdateMsg> cursor,
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final CSN startCSN,
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final PositionStrategy positionStrategy) {
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this.cursor = cursor;
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this.lastNonNullCurrentCSN = startCSN;
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this.positionStrategy = positionStrategy;
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}
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/** {@inheritDoc} */
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@Override
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public UpdateMsg getRecord()
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{
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return nextRecord == null ? null : nextRecord.getValue();
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}
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/** {@inheritDoc} */
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@Override
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public boolean next() throws ChangelogException
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{
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if (cursor.next())
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{
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nextRecord = cursor.getRecord();
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final int nextCSNCompare = nextRecord.getKey().compareTo(lastNonNullCurrentCSN);
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if (nextCSNCompare > 0 || (nextCSNCompare == 0 && positionStrategy == ON_MATCHING_KEY))
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{
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// start CSN is found, switch to position strategy that always find the next
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lastNonNullCurrentCSN = nextRecord.getKey();
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positionStrategy = AFTER_MATCHING_KEY;
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return true;
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}
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}
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// either cursor is exhausted or we still have not reached the start CSN
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return nextWhenCursorIsExhaustedOrNotCorrectlyPositionned();
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}
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/** Re-initialize the cursor after the last non null CSN. */
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private boolean nextWhenCursorIsExhaustedOrNotCorrectlyPositionned() throws ChangelogException
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{
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final boolean found = cursor.positionTo(lastNonNullCurrentCSN, GREATER_THAN_OR_EQUAL_TO_KEY, positionStrategy);
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if (found && cursor.next())
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{
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nextRecord = cursor.getRecord();
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lastNonNullCurrentCSN = nextRecord.getKey();
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return true;
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}
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nextRecord = null;
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return false;
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}
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/** {@inheritDoc} */
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@Override
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public void close()
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{
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cursor.close();
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}
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}
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