org.h2.command.Command Maven / Gradle / Ivy
/*
* Copyright 2004-2019 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.command;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Set;
import java.util.concurrent.TimeUnit;
import org.h2.api.ErrorCode;
import org.h2.engine.Constants;
import org.h2.engine.Database;
import org.h2.engine.DbObject;
import org.h2.engine.Session;
import org.h2.expression.ParameterInterface;
import org.h2.message.DbException;
import org.h2.message.Trace;
import org.h2.result.ResultInterface;
import org.h2.result.ResultWithGeneratedKeys;
import org.h2.result.ResultWithPaddedStrings;
import org.h2.util.MathUtils;
/**
* 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 last start time.
*/
protected long startTimeNanos;
/**
* The trace module.
*/
private final Trace trace;
/**
* If this query was canceled.
*/
private volatile boolean cancel;
private final String sql;
private boolean canReuse;
Command(Session session, String sql) {
this.session = session;
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
*/
@Override
public abstract boolean isQuery();
/**
* Prepare join batching.
*/
public abstract void prepareJoinBatch();
/**
* Get the list of parameters.
*
* @return the list of parameters
*/
@Override
public abstract ArrayList 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();
/**
* Execute an updating statement (for example insert, delete, or update), if
* this is possible.
*
* @param generatedKeysRequest
* {@code false} if generated keys are not needed, {@code true} if
* generated keys should be configured automatically, {@code int[]}
* to specify column indices to return generated keys from, or
* {@code String[]} to specify column names to return generated keys
* from
* @return the update count and generated keys, if any
* @throws DbException if the command is not an updating statement
*/
public abstract ResultWithGeneratedKeys update(Object generatedKeysRequest);
/**
* Execute a query statement, if this is possible.
*
* @param maxrows the maximum number of rows returned
* @return the local result set
* @throws DbException if the command is not a query
*/
public abstract ResultInterface query(int maxrows);
@Override
public final ResultInterface getMetaData() {
return queryMeta();
}
/**
* Start the stopwatch.
*/
void start() {
if (trace.isInfoEnabled() || session.getDatabase().getQueryStatistics()) {
startTimeNanos = System.nanoTime();
}
}
void setProgress(int state) {
session.getDatabase().setProgress(state, sql, 0, 0);
}
/**
* Check if this command has been canceled, and throw an exception if yes.
*
* @throws DbException if the statement has been canceled
*/
protected void checkCanceled() {
if (cancel) {
cancel = false;
throw DbException.get(ErrorCode.STATEMENT_WAS_CANCELED);
}
}
@Override
public void stop() {
if (!isTransactional()) {
session.commit(true);
} else if (session.getAutoCommit()) {
session.commit(false);
}
if (trace.isInfoEnabled() && startTimeNanos > 0) {
long timeMillis = (System.nanoTime() - startTimeNanos) / 1000 / 1000;
if (timeMillis > Constants.SLOW_QUERY_LIMIT_MS) {
trace.info("slow query: {0} ms", timeMillis);
}
}
}
/**
* 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
*/
@Override
public ResultInterface executeQuery(int maxrows, boolean scrollable) {
startTimeNanos = 0;
long start = 0;
Database database = session.getDatabase();
Object sync = database.isMVStore() ? session : database;
session.waitIfExclusiveModeEnabled();
boolean callStop = true;
//noinspection SynchronizationOnLocalVariableOrMethodParameter
synchronized (sync) {
session.startStatementWithinTransaction(this);
try {
while (true) {
database.checkPowerOff();
try {
ResultInterface result = query(maxrows);
callStop = !result.isLazy();
if (database.getMode().padFixedLengthStrings) {
return ResultWithPaddedStrings.get(result);
}
return result;
} catch (DbException e) {
start = filterConcurrentUpdate(e, start);
} catch (OutOfMemoryError e) {
callStop = false;
// there is a serious problem:
// the transaction may be applied partially
// in this case we need to panic:
// close the database
database.shutdownImmediately();
throw DbException.convert(e);
} catch (Throwable e) {
throw DbException.convert(e);
}
}
} catch (DbException e) {
e = e.addSQL(sql);
SQLException s = e.getSQLException();
database.exceptionThrown(s, sql);
if (s.getErrorCode() == ErrorCode.OUT_OF_MEMORY) {
callStop = false;
database.shutdownImmediately();
throw e;
}
database.checkPowerOff();
throw e;
} finally {
session.endStatement();
if (callStop) {
stop();
}
}
}
}
@Override
public ResultWithGeneratedKeys executeUpdate(Object generatedKeysRequest) {
long start = 0;
Database database = session.getDatabase();
Object sync = database.isMVStore() ? session : database;
session.waitIfExclusiveModeEnabled();
boolean callStop = true;
//noinspection SynchronizationOnLocalVariableOrMethodParameter
synchronized (sync) {
Session.Savepoint rollback = session.setSavepoint();
session.startStatementWithinTransaction(this);
DbException ex = null;
try {
while (true) {
database.checkPowerOff();
try {
return update(generatedKeysRequest);
} catch (DbException e) {
start = filterConcurrentUpdate(e, start);
} catch (OutOfMemoryError e) {
callStop = false;
database.shutdownImmediately();
throw DbException.convert(e);
} catch (Throwable e) {
throw DbException.convert(e);
}
}
} catch (DbException e) {
e = e.addSQL(sql);
SQLException s = e.getSQLException();
database.exceptionThrown(s, sql);
if (s.getErrorCode() == ErrorCode.OUT_OF_MEMORY) {
callStop = false;
database.shutdownImmediately();
throw e;
}
try {
database.checkPowerOff();
if (s.getErrorCode() == ErrorCode.DEADLOCK_1) {
session.rollback();
} else {
session.rollbackTo(rollback);
}
} catch (Throwable nested) {
e.addSuppressed(nested);
}
ex = e;
throw e;
} finally {
try {
session.endStatement();
if (callStop) {
stop();
}
} catch (Throwable nested) {
if (ex == null) {
throw nested;
} else {
ex.addSuppressed(nested);
}
}
}
}
}
private long filterConcurrentUpdate(DbException e, long start) {
int errorCode = e.getErrorCode();
if (errorCode != ErrorCode.CONCURRENT_UPDATE_1 &&
errorCode != ErrorCode.ROW_NOT_FOUND_IN_PRIMARY_INDEX &&
errorCode != ErrorCode.ROW_NOT_FOUND_WHEN_DELETING_1) {
throw e;
}
long now = System.nanoTime();
if (start != 0 && TimeUnit.NANOSECONDS.toMillis(now - start) > session.getLockTimeout()) {
throw DbException.get(ErrorCode.LOCK_TIMEOUT_1, e);
}
// Only in PageStore mode we need to sleep here to avoid busy wait loop
Database database = session.getDatabase();
if (!database.isMVStore()) {
int sleep = 1 + MathUtils.randomInt(10);
while (true) {
try {
// although nobody going to notify us
// it is vital to give up lock on a database
database.wait(sleep);
} catch (InterruptedException e1) {
// ignore
}
long slept = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - now);
if (slept >= sleep) {
break;
}
}
}
return start == 0 ? now : start;
}
@Override
public void close() {
canReuse = true;
}
@Override
public void cancel() {
this.cancel = true;
}
@Override
public String toString() {
return sql + Trace.formatParams(getParameters());
}
public boolean isCacheable() {
return false;
}
/**
* Whether the command is already closed (in which case it can be re-used).
*
* @return true if it can be re-used
*/
public boolean canReuse() {
return canReuse;
}
/**
* The command is now re-used, therefore reset the canReuse flag, and the
* parameter values.
*/
public void reuse() {
canReuse = false;
ArrayList parameters = getParameters();
for (ParameterInterface param : parameters) {
param.setValue(null, true);
}
}
public void setCanReuse(boolean canReuse) {
this.canReuse = canReuse;
}
public abstract Set getDependencies();
}