org.h2.command.Command Maven / Gradle / Ivy
/*
* Copyright 2004-2010 H2 Group. Multiple-Licensed under the H2 License,
* Version 1.0, and under the Eclipse Public License, Version 1.0
* (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.command;
import java.sql.SQLException;
import org.h2.constant.ErrorCode;
import org.h2.engine.Constants;
import org.h2.engine.Database;
import org.h2.engine.Session;
import org.h2.expression.ParameterInterface;
import org.h2.message.Message;
import org.h2.message.Trace;
import org.h2.message.TraceObject;
import org.h2.result.ResultInterface;
import org.h2.util.ObjectArray;
/**
* Represents a SQL statement. This object is only used on the server side.
*/
public abstract class Command implements CommandInterface {
/**
* The session.
*/
protected final Session session;
/**
* The trace module.
*/
protected final Trace trace;
/**
* The last start time.
*/
protected long startTime;
/**
* If this query was canceled.
*/
private volatile boolean cancel;
private final String sql;
public Command(Parser parser, String sql) {
this.session = parser.getSession();
this.sql = sql;
trace = session.getDatabase().getTrace(Trace.COMMAND);
}
/**
* Check if this command is transactional.
* If it is not, then it forces the current transaction to commit.
*
* @return true if it is
*/
public abstract boolean isTransactional();
/**
* Check if this command is a query.
*
* @return true if it is
*/
public abstract boolean isQuery();
/**
* Get the list of parameters.
*
* @return the list of parameters
*/
public abstract ObjectArray< ? extends ParameterInterface> getParameters();
/**
* Check if this command is read only.
*
* @return true if it is
*/
public abstract boolean isReadOnly();
/**
* Get an empty result set containing the meta data.
*
* @return an empty result set
*/
public abstract ResultInterface queryMeta() throws SQLException;
/**
* Execute an updating statement, if this is possible.
*
* @return the update count
* @throws SQLException if the command is not an updating statement
*/
public int update() throws SQLException {
throw Message.getSQLException(ErrorCode.METHOD_NOT_ALLOWED_FOR_QUERY);
}
/**
* Execute a query statement, if this is possible.
*
* @param maxrows the maximum number of rows returned
* @return the local result set
* @throws SQLException if the command is not a query
*/
public ResultInterface query(int maxrows) throws SQLException {
throw Message.getSQLException(ErrorCode.METHOD_ONLY_ALLOWED_FOR_QUERY);
}
public final ResultInterface getMetaData() throws SQLException {
return queryMeta();
}
/**
* Execute a query and return the result.
* This method prepares everything and calls {@link #query(int)} finally.
*
* @param maxrows the maximum number of rows to return
* @param scrollable if the result set must be scrollable (ignored)
* @return the result set
*/
public ResultInterface executeQuery(int maxrows, boolean scrollable) throws SQLException {
startTime = System.currentTimeMillis();
Database database = session.getDatabase();
Object sync = database.isMultiThreaded() ? (Object) session : (Object) database;
session.waitIfExclusiveModeEnabled();
synchronized (sync) {
try {
database.checkPowerOff();
session.setCurrentCommand(this, startTime);
return query(maxrows);
} catch (Exception e) {
SQLException s = Message.convert(e, sql);
database.exceptionThrown(s, sql);
throw s;
} finally {
stop();
}
}
}
/**
* Start the stopwatch.
*/
void start() {
startTime = System.currentTimeMillis();
}
/**
* Check if this command has been canceled, and throw an exception if yes.
*
* @throws SQLException if the statement has been canceled
*/
public void checkCanceled() throws SQLException {
if (cancel) {
cancel = false;
throw Message.getSQLException(ErrorCode.STATEMENT_WAS_CANCELED);
}
}
private void stop() throws SQLException {
session.closeTemporaryResults();
session.setCurrentCommand(null, 0);
if (!isTransactional()) {
session.commit(true);
} else if (session.getAutoCommit()) {
session.commit(false);
} else if (session.getDatabase().isMultiThreaded()) {
Database db = session.getDatabase();
if (db != null) {
if (db.getLockMode() == Constants.LOCK_MODE_READ_COMMITTED) {
session.unlockReadLocks();
}
}
}
if (trace.isInfoEnabled()) {
long time = System.currentTimeMillis() - startTime;
if (time > Constants.SLOW_QUERY_LIMIT_MS) {
trace.info("slow query: " + time);
}
}
}
public int executeUpdate() throws SQLException {
long start = startTime = System.currentTimeMillis();
Database database = session.getDatabase();
Object sync = database.isMultiThreaded() ? (Object) session : (Object) database;
session.waitIfExclusiveModeEnabled();
boolean callStop = true;
session.getDatabase().beforeWriting();
synchronized (sync) {
int rollback = session.getLogId();
session.setCurrentCommand(this, startTime);
try {
while (true) {
database.checkPowerOff();
try {
return update();
} catch (SQLException e) {
if (e.getErrorCode() == ErrorCode.CONCURRENT_UPDATE_1) {
long now = System.currentTimeMillis();
if (now - start > session.getLockTimeout()) {
throw Message.getSQLException(ErrorCode.LOCK_TIMEOUT_1, e, "");
}
try {
if (sync == database) {
database.wait(10);
} else {
Thread.sleep(10);
}
} catch (InterruptedException e1) {
// ignore
}
continue;
}
throw e;
} catch (Exception e) {
throw Message.convert(e);
} catch (Throwable e) {
throw Message.convertThrowable(e);
}
}
} catch (SQLException e) {
Message.addSQL(e, sql);
database.exceptionThrown(e, sql);
database.checkPowerOff();
if (e.getErrorCode() == ErrorCode.DEADLOCK_1) {
session.rollback();
} else if (e.getErrorCode() == ErrorCode.OUT_OF_MEMORY) {
// there is a serious problem:
// the transaction may be applied partially
// in this case we need to panic:
// close the database
callStop = false;
session.getDatabase().shutdownImmediately();
throw e;
} else {
session.rollbackTo(rollback, false);
}
throw e;
} finally {
try {
if (callStop) {
stop();
}
} finally {
session.getDatabase().afterWriting();
}
}
}
}
public void close() {
// nothing to do
}
public void cancel() {
this.cancel = true;
}
public String toString() {
return TraceObject.toString(sql, getParameters());
}
}