+
−/*
+
− * This Source Code Form is subject to the terms of the Mozilla Public
+
− * License, v. 2.0.  If a copy of the MPL was not distributed with this
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− * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
− *
+
− * Copyright 1997 - July 2008 CWI, August 2008 - 2016 MonetDB B.V.
+
− */
+
−
+
−package nl.cwi.monetdb.jdbc;
+
−
+
−import java.sql.*;
+
−import java.util.concurrent.atomic.AtomicInteger;
+
−
+
−/**
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− * The representation of a savepoint, which is a point within the current
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− * transaction that can be referenced from the Connection.rollback method.
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− * When a transaction is rolled back to a savepoint all changes made after
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− * that savepoint are undone.
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− * Savepoints can be either named or unnamed. Unnamed savepoints are
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− * identified by an ID generated by the underlying data source.
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− *
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− * This little class is nothing more than a container for a name and/or
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− * an id. Each instance of this class always has an id, which is used for
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− * internal representation of the save point.
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− *
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− * Because the IDs which get generated are a logical sequence, application
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− * wide, two concurrent transactions are guaranteed to not to have the same
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− * save point identifiers. In this implementation the validaty of save points
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− * is determined by the server, which makes this a light implementation.
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− *
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− * @author Fabian Groffen
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− * @version 1.0
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− */
+
−public class MonetSavepoint implements Savepoint {
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−	/** The id of the last created Savepoint */
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−	private static AtomicInteger highestId = new AtomicInteger(0);
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−
+
−	/** The name of this Savepoint */
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−	private final String name;
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−	/** The id of this Savepoint */
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−	private final int id;
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−
+
−	public MonetSavepoint(String name) throws IllegalArgumentException {
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−		if (name == null) throw new IllegalArgumentException("null not allowed");
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−
+
−		this.id = getNextId();
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−		this.name = name;
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−	}
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−
+
−	public MonetSavepoint() {
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−		this.id = getNextId();
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−		this.name = null;
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−	}
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−
+
−	/**
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−	 * Retrieves the generated ID for the savepoint that this Savepoint object
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−	 * represents.
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−	 *
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−	 * @return the numeric ID of this savepoint
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−	 * @throws SQLException if this is a named savepoint
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−	 */
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−	@Override
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−	public int getSavepointId() throws SQLException {
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−		if (name != null) throw
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−			new SQLException("Cannot getID for named savepoint", "3B000");
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−
+
−		return getId();
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−	}
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−
+
−	/**
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−	 * Retrieves the name of the savepoint that this Savepoint object
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−	 * represents.
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−	 *
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−	 * @return the name of this savepoint
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−	 * @throws SQLException if this is an un-named savepoint
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−	 */
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−	@Override
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−	public String getSavepointName() throws SQLException {
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−		if (name == null) throw
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−			new SQLException("Unable to retrieve name of unnamed savepoint", "3B000");
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−
+
−		return name;
+
−	}
+
−
+
−	//== end of methods from Savepoint interface
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−
+
−	/**
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−	 * Retrieves the savepoint id, like the getSavepointId method with the only
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−	 * difference that this method will always return the id, regardless of
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−	 * whether it is named or not.
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−	 *
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−	 * @return the numeric ID of this savepoint
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−	 */
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−	int getId() {
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−		return id;
+
−	}
+
−
+
−	/**
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−	 * Returns the name to use when referencing this save point to the MonetDB
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−	 * database. The returned value is guaranteed to be unique and consists of
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−	 * a prefix string and a sequence number.
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−	 *
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−	 * @return the unique savepoint name
+
−	 */
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−	String getName() {
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−		return "MonetDBSP" + id;
+
−	}
+
−
+
−
+
−	/**
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−	 * Returns the next id, which is larger than the last returned id. This
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−	 * method is synchronized to prevent race conditions. Since this is static
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−	 * code, this method is shared by requests from multiple Connection objects.
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−	 * Therefore two successive calls to this method need not to have a
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−	 * difference of 1.
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−	 *
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−	 * @return the next int which is guaranteed to be higher than the one
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−	 *         at the last call to this method.
+
−	 */
+
−	private static int getNextId() {
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−		return highestId.incrementAndGet();
+
−	}
+
−
+
−	/**
+
−	 * Returns the highest id returned by getNextId(). This method is also
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−	 * synchronized to prevent race conditions and thus guaranteed to be
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−	 * thread-safe.
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−	 *
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−	 * @return the highest id returned by a call to getNextId()
+
−	 */
+
−	private static int getHighestId() {
+
−		return highestId.get();
+
−	}
+
−}