Mysql PreparedStatement 批处理

阅读更多

JDBC驱动初始化-Mysql: http://donald-draper.iteye.com/blog/2342010
JDBC连接的获取： http://donald-draper.iteye.com/blog/2342011
Mysql负载均衡连接的获取： http://donald-draper.iteye.com/blog/2342089
Mysql主从复制读写分离连接的获取： http://donald-draper.iteye.com/blog/2342108
ConnectionImp创建MysqlIO ： http://donald-draper.iteye.com/blog/2342959
Mysql预编译SQL： http://donald-draper.iteye.com/blog/2342960
MysqlSQL PreparedStatement的查询: http://donald-draper.iteye.com/blog/2343083
MySQL ServerPreparedStatement查询： http://donald-draper.iteye.com/blog/2343124
在前文中，我们讲过statment的查询，今天来看一下批处理，在看批处理之前，statement设值
//设值

public void setString(int parameterIndex, String x)
        throws SQLException
    {
        if(x == null)
        {
            setNull(parameterIndex, 1);
        } else
        {
            checkClosed();
            int stringLength = x.length();
            if(connection.isNoBackslashEscapesSet())
            {
                boolean needsHexEscape = isEscapeNeededForString(x, stringLength);
                if(!needsHexEscape)
                {
                    byte parameterAsBytes[] = null;
                    StringBuffer quotedString = new StringBuffer(x.length() + 2);
                    quotedString.append('\'');
                    quotedString.append(x);
                    quotedString.append('\'');
                    if(!isLoadDataQuery)
                        parameterAsBytes = StringUtils.getBytes(quotedString.toString(), charConverter, charEncoding, connection.getServerCharacterEncoding(), connection.parserKnowsUnicode(), getExceptionInterceptor());
                    else
                        parameterAsBytes = quotedString.toString().getBytes();
	            //将String转换为bytes，设值
                    setInternal(parameterIndex, parameterAsBytes);
                } else
                {
                    byte parameterAsBytes[] = null;
                    if(!isLoadDataQuery)
                        parameterAsBytes = StringUtils.getBytes(x, charConverter, charEncoding, connection.getServerCharacterEncoding(), connection.parserKnowsUnicode(), getExceptionInterceptor());
                    else
                        parameterAsBytes = x.getBytes();
	              //将String转换为bytes，设值
                    setBytes(parameterIndex, parameterAsBytes);
                }
                return;
            }
            String parameterAsString = x;
            boolean needsQuoted = true;
            if(isLoadDataQuery || isEscapeNeededForString(x, stringLength))
            {
                needsQuoted = false;
                StringBuffer buf = new StringBuffer((int)((double)x.length() * 1.1000000000000001D));
                buf.append('\'');
                for(int i = 0; i < stringLength; i++)
                {
                    char c = x.charAt(i);
                    switch(c)
                    {
                    default:
                        break;

                    case 0: // '\0'
                        buf.append('\\');
                        buf.append('0');
                        continue;

                    case 10: // '\n'
                        buf.append('\\');
                        buf.append('n');
                        continue;

                    case 13: // '\r'
                        buf.append('\\');
                        buf.append('r');
                        continue;

                    case 92: // '\\'
                        buf.append('\\');
                        buf.append('\\');
                        continue;

                    case 39: // '\''
                        buf.append('\\');
                        buf.append('\'');
                        continue;

                    case 34: // '"'
                        if(usingAnsiMode)
                            buf.append('\\');
                        buf.append('"');
                        continue;

                    case 26: // '\032'
                        buf.append('\\');
                        buf.append('Z');
                        continue;

                    case 165: 
                    case 8361: 
                        if(charsetEncoder != null)
                        {
                            CharBuffer cbuf = CharBuffer.allocate(1);
                            ByteBuffer bbuf = ByteBuffer.allocate(1);
                            cbuf.put(c);
                            cbuf.position(0);
                            charsetEncoder.encode(cbuf, bbuf, true);
                            if(bbuf.get(0) == 92)
                                buf.append('\\');
                        }
                        break;
                    }
                    buf.append(c);
                }

                buf.append('\'');
                parameterAsString = buf.toString();
            }
            byte parameterAsBytes[] = null;
            if(!isLoadDataQuery)
            {
                if(needsQuoted)
                    parameterAsBytes = StringUtils.getBytesWrapped(parameterAsString, '\'', '\'', charConverter, charEncoding, connection.getServerCharacterEncoding(), connection.parserKnowsUnicode(), getExceptionInterceptor());
                else
                    parameterAsBytes = StringUtils.getBytes(parameterAsString, charConverter, charEncoding, connection.getServerCharacterEncoding(), connection.parserKnowsUnicode(), getExceptionInterceptor());
            } else
            {
                parameterAsBytes = parameterAsString.getBytes();
            }
            setInternal(parameterIndex, parameterAsBytes);
            parameterTypes[(parameterIndex - 1) + getParameterIndexOffset()] = 12;
        }
    }

我们先看一下Prepare内部变量，再看setInternal方法
//描述PrepareStatement的参数信息，PrepareStatement的变量

private boolean isNull[];参数是否为null
private boolean isStream[];//参数是不是流CLOB或BLOB
protected int numberOfExecutions;
protected String originalSql;
protected int parameterCount;//参数数量
protected MysqlParameterMetadata parameterMetaData;
private InputStream parameterStreams[];//参数流
private byte parameterValues[][];//参数值
protected int parameterTypes[];//参数类型

现在来看setInternal方法

protected final void setInternal(int paramIndex, byte val[])
        throws SQLException
    {
        if(isClosed)
        {
            throw SQLError.createSQLException(Messages.getString("PreparedStatement.48"), "S1009", getExceptionInterceptor());
        } else
        {
            int parameterIndexOffset = getParameterIndexOffset();
            checkBounds(paramIndex, parameterIndexOffset);
            //paramIndex对应的参数是不是流
            isStream[(paramIndex - 1) + parameterIndexOffset] = false;
	    //paramIndex对应的参数是不是null
            isNull[(paramIndex - 1) + parameterIndexOffset] = false;
            //paramIndex对应的参数流
            parameterStreams[(paramIndex - 1) + parameterIndexOffset] = null;
	    //paramIndex对应的参数值
            parameterValues[(paramIndex - 1) + parameterIndexOffset] = val;
            return;
        }
    }
     public void setBytes(int parameterIndex, byte x[])
        throws SQLException
    {
        setBytes(parameterIndex, x, true, true);
        if(x != null)
            parameterTypes[(parameterIndex - 1) + getParameterIndexOffset()] = -2;
    }

    protected void setBytes(int parameterIndex, byte x[], boolean checkForIntroducer, boolean escapeForMBChars)
        throws SQLException
    {
        if(x == null)
        {
            setNull(parameterIndex, -2);
        } else
        {
            String connectionEncoding = connection.getEncoding();
            if(connection.isNoBackslashEscapesSet() || escapeForMBChars && connection.getUseUnicode() && connectionEncoding != null && CharsetMapping.isMultibyteCharset(connectionEncoding))
            {
                ByteArrayOutputStream bOut = new ByteArrayOutputStream(x.length * 2 + 3);
                bOut.write(120);
                bOut.write(39);
                for(int i = 0; i < x.length; i++)
                {
                    int lowBits = (x[i] & 255) / 16;
                    int highBits = (x[i] & 255) % 16;
                    bOut.write(HEX_DIGITS[lowBits]);
                    bOut.write(HEX_DIGITS[highBits]);
                }

                bOut.write(39);
                setInternal(parameterIndex, bOut.toByteArray());
                return;
            }
            int numBytes = x.length;
            int pad = 2;
            boolean needsIntroducer = checkForIntroducer && connection.versionMeetsMinimum(4, 1, 0);
            if(needsIntroducer)
                pad += 7;
            ByteArrayOutputStream bOut = new ByteArrayOutputStream(numBytes + pad);
            if(needsIntroducer)
            {
                bOut.write(95);
                bOut.write(98);
                bOut.write(105);
                bOut.write(110);
                bOut.write(97);
                bOut.write(114);
                bOut.write(121);
            }
            bOut.write(39);
            for(int i = 0; i < numBytes; i++)
            {
                byte b = x[i];
                switch(b)
                {
                case 0: // '\0'
                    bOut.write(92);
                    bOut.write(48);
                    break;

                case 10: // '\n'
                    bOut.write(92);
                    bOut.write(110);
                    break;

                case 13: // '\r'
                    bOut.write(92);
                    bOut.write(114);
                    break;

                case 92: // '\\'
                    bOut.write(92);
                    bOut.write(92);
                    break;

                case 39: // '\''
                    bOut.write(92);
                    bOut.write(39);
                    break;

                case 34: // '"'
                    bOut.write(92);
                    bOut.write(34);
                    break;

                case 26: // '\032'
                    bOut.write(92);
                    bOut.write(90);
                    break;

                default:
                    bOut.write(b);
                    break;
                }
            }

            bOut.write(39);
	    //最后还是委托给setInternal
            setInternal(parameterIndex, bOut.toByteArray());
        }
}

从上面可以看出，preparestatment设值，就是将值是否为null，是否是流，参数值，参数流信息放到statement
的isNull，isStream，parameterStreams，parameterValues中。
//添加到批处理
 

  public void addBatch()
        throws SQLException
    {
        if(batchedArgs == null)
            batchedArgs = new ArrayList();
        for(int i = 0; i < parameterValues.length; i++)
            checkAllParametersSet(parameterValues[i], parameterStreams[i], i);
        batchedArgs.add(new BatchParams(parameterValues, parameterStreams, isStream, streamLengths, isNull));
    }

//批参数

 class BatchParams
    {

        boolean isNull[];
        boolean isStream[];
        InputStream parameterStreams[];
        byte parameterStrings[][];
        int streamLengths[];

        BatchParams(byte strings[][], InputStream streams[], boolean isStreamFlags[], int lengths[], boolean isNullFlags[])
        {
            isNull = null;
            isStream = null;
            parameterStreams = null;
            parameterStrings = (byte[][])null;
            streamLengths = null;
            parameterStrings = new byte[strings.length][];
            parameterStreams = new InputStream[streams.length];
            isStream = new boolean[isStreamFlags.length];
            streamLengths = new int[lengths.length];
            isNull = new boolean[isNullFlags.length];
            System.arraycopy(strings, 0, parameterStrings, 0, strings.length);
            System.arraycopy(streams, 0, parameterStreams, 0, streams.length);
            System.arraycopy(isStreamFlags, 0, isStream, 0, isStreamFlags.length);
            System.arraycopy(lengths, 0, streamLengths, 0, lengths.length);
            System.arraycopy(isNullFlags, 0, isNull, 0, isNullFlags.length);
        }
}

//批处理sql

public synchronized void addBatch(String sql)
        throws SQLException
    {
        batchHasPlainStatements = true;
	//委托给父类StatementImpl
        super.addBatch(sql);
    }
//StatementImpl
    public synchronized void addBatch(String sql)
        throws SQLException
    {
        if(batchedArgs == null)
            batchedArgs = new ArrayList();
        if(sql != null)
            batchedArgs.add(sql);
    }

//批执行

public int[] executeBatch()
        throws SQLException
    {
        checkClosed();
        if(connection.isReadOnly())
            throw new SQLException(Messages.getString("PreparedStatement.25") + Messages.getString("PreparedStatement.26"), "S1009");
        //获取互斥锁
	Object obj = connection.getMutex();
        JVM INSTR monitorenter ;
        if(batchedArgs == null || batchedArgs.size() == 0)
            return new int[0];
        int batchTimeout;
        batchTimeout = timeoutInMillis;
        timeoutInMillis = 0;
        resetCancelledState();
        int ai[];
        clearWarnings();
        if(batchHasPlainStatements || !connection.getRewriteBatchedStatements())
            break MISSING_BLOCK_LABEL_195;
        if(!canRewriteAsMultiValueInsertAtSqlLevel())
            break MISSING_BLOCK_LABEL_141;
	//执行批插入
        ai = executeBatchedInserts(batchTimeout);
        clearBatch();
        obj;
        JVM INSTR monitorexit ;
        return ai;
        if(!connection.versionMeetsMinimum(4, 1, 0) || batchHasPlainStatements || batchedArgs == null || batchedArgs.size() <= 3)
            break MISSING_BLOCK_LABEL_195;
	//执行批PrepareStatment
        ai = executePreparedBatchAsMultiStatement(batchTimeout);
        clearBatch();
    }

来看一下，批量插入

protected int[] executeBatchedInserts(int batchTimeout)
        throws SQLException
    {
        Connection locallyScopedConn;
	//批量大小
        int numBatchedArgs;
	//每批的大小
        int numValuesPerBatch;
	//batch处理statement
        java.sql.PreparedStatement batchedStatement;
	//batch参数index
        int batchedParamIndex;
        int updateCountRunningTotal;
        int batchCounter;
	//延时statement任务
        StatementImpl.CancelTask timeoutTask;
        SQLException sqlEx;
        int updateCounts[];
        String valuesClause = getValuesClause();
	//连接
        locallyScopedConn = connection;
        if(valuesClause == null)
            return executeBatchSerially(batchTimeout);
	//批量大小
        numBatchedArgs = batchedArgs.size();
        if(retrieveGeneratedKeys)
            batchedGeneratedKeys = new ArrayList(numBatchedArgs);
	//计算每批的大小
        numValuesPerBatch = computeBatchSize(numBatchedArgs);
        if(numBatchedArgs < numValuesPerBatch)
            numValuesPerBatch = numBatchedArgs;
        batchedStatement = null;
        batchedParamIndex = 1;
        updateCountRunningTotal = 0;
        int numberToExecuteAsMultiValue = 0;
        batchCounter = 0;
        timeoutTask = null;
        sqlEx = null;
        updateCounts = new int[numBatchedArgs];
        for(int i = 0; i < batchedArgs.size(); i++)
            updateCounts[i] = 1;

        batchedStatement = prepareBatchedInsertSQL((ConnectionImpl)locallyScopedConn, numValuesPerBatch);
        if(connection.getEnableQueryTimeouts() && batchTimeout != 0 && connection.versionMeetsMinimum(5, 0, 0))
        {
            timeoutTask = new StatementImpl.CancelTask(this, (StatementImpl)batchedStatement);
            ConnectionImpl.getCancelTimer().schedule(timeoutTask, batchTimeout);
        }
        int numberToExecuteAsMultiValue;
        if(numBatchedArgs < numValuesPerBatch)
            numberToExecuteAsMultiValue = numBatchedArgs;
        else
            numberToExecuteAsMultiValue = numBatchedArgs / numValuesPerBatch;
        int numberArgsToExecute = numberToExecuteAsMultiValue * numValuesPerBatch;
        for(int i = 0; i < numberArgsToExecute; i++)
        {
            if(i != 0 && i % numValuesPerBatch == 0)
            {
                try
                {
                    updateCountRunningTotal += batchedStatement.executeUpdate();
                }
                catch(SQLException ex)
                {
                    sqlEx = handleExceptionForBatch(batchCounter - 1, numValuesPerBatch, updateCounts, ex);
                }
                getBatchedGeneratedKeys(batchedStatement);
                batchedStatement.clearParameters();
                batchedParamIndex = 1;
            }
            batchedParamIndex = setOneBatchedParameterSet(batchedStatement, batchedParamIndex, batchedArgs.get(batchCounter++));
        }

        try
        {
            updateCountRunningTotal += batchedStatement.executeUpdate();
        }
        catch(SQLException ex)
        {
            sqlEx = handleExceptionForBatch(batchCounter - 1, numValuesPerBatch, updateCounts, ex);
        }
        getBatchedGeneratedKeys(batchedStatement);
        numValuesPerBatch = numBatchedArgs - batchCounter;
     
        int ai[];
	//分批次，执行更新
        if(numValuesPerBatch > 0)
        {
            batchedStatement = prepareBatchedInsertSQL((ConnectionImpl)locallyScopedConn, numValuesPerBatch);
            if(timeoutTask != null)
                timeoutTask.toCancel = (StatementImpl)batchedStatement;
            for(batchedParamIndex = 1; batchCounter < numBatchedArgs; batchedParamIndex = setOneBatchedParameterSet(batchedStatement, batchedParamIndex, batchedArgs.get(batchCounter++)));
            try
            {
	        //更新
                updateCountRunningTotal += batchedStatement.executeUpdate();
            }
            catch(SQLException ex)
            {
                sqlEx = handleExceptionForBatch(batchCounter - 1, numValuesPerBatch, updateCounts, ex);
            }
            getBatchedGeneratedKeys(batchedStatement);
        }
        ai = updateCounts;
        if(batchedStatement != null)
            batchedStatement.close();
        return ai;
    }
在看执行更新
public int executeUpdate()
        throws SQLException
    {
        return executeUpdate(true, false);
    }

    protected int executeUpdate(boolean clearBatchedGeneratedKeysAndWarnings, boolean isBatch)
        throws SQLException
    {
        if(clearBatchedGeneratedKeysAndWarnings)
        {
            clearWarnings();
            batchedGeneratedKeys = null;
        }
        return executeUpdate(parameterValues, parameterStreams, isStream, streamLengths, isNull, isBatch);
    }
//执行更新
    protected int executeUpdate(byte batchedParameterStrings[][], InputStream batchedParameterStreams[], boolean batchedIsStream[], int batchedStreamLengths[], boolean batchedIsNull[], boolean isReallyBatch)
        throws SQLException
    {
        checkClosed();
        ConnectionImpl locallyScopedConn = connection;
        if(locallyScopedConn.isReadOnly())
            throw SQLError.createSQLException(Messages.getString("PreparedStatement.34") + Messages.getString("PreparedStatement.35"), "S1009", getExceptionInterceptor());
        if(firstCharOfStmt == 'S' && isSelectQuery())
            throw SQLError.createSQLException(Messages.getString("PreparedStatement.37"), "01S03", getExceptionInterceptor());
        if(results != null && !locallyScopedConn.getHoldResultsOpenOverStatementClose())
            results.realClose(false);
	//返回结果
        ResultSetInternalMethods rs = null;
        synchronized(locallyScopedConn.getMutex())
        {
	   //填充更新包
            Buffer sendPacket = fillSendPacket(batchedParameterStrings, batchedParameterStreams, batchedIsStream, batchedStreamLengths);
            String oldCatalog = null;
            if(!locallyScopedConn.getCatalog().equals(currentCatalog))
            {
                oldCatalog = locallyScopedConn.getCatalog();
                locallyScopedConn.setCatalog(currentCatalog);
            }
            if(locallyScopedConn.useMaxRows())
                executeSimpleNonQuery(locallyScopedConn, "SET OPTION SQL_SELECT_LIMIT=DEFAULT");
            boolean oldInfoMsgState = false;
            if(retrieveGeneratedKeys)
            {
                oldInfoMsgState = locallyScopedConn.isReadInfoMsgEnabled();
                locallyScopedConn.setReadInfoMsgEnabled(true);
            }
	    //内部执行更新，这个我们在前面，看过，今天再看一下，只看关键
            rs = executeInternal(-1, sendPacket, false, false, null, isReallyBatch);
            if(retrieveGeneratedKeys)
            {
                locallyScopedConn.setReadInfoMsgEnabled(oldInfoMsgState);
                rs.setFirstCharOfQuery(firstCharOfStmt);
            }
            if(oldCatalog != null)
                locallyScopedConn.setCatalog(oldCatalog);
        }
        results = rs;
        updateCount = rs.getUpdateCount();
        if(containsOnDuplicateKeyUpdateInSQL() && compensateForOnDuplicateKeyUpdate && (updateCount == 2L || updateCount == 0L))
            updateCount = 1L;
        int truncatedUpdateCount = 0;
        if(updateCount > 2147483647L)
            truncatedUpdateCount = 2147483647;
        else
            truncatedUpdateCount = (int)updateCount;
        lastInsertId = rs.getUpdateID();
        return truncatedUpdateCount;
    }

//执行更新

protected ResultSetInternalMethods executeInternal(int maxRowsToRetrieve, Buffer sendPacket, boolean createStreamingResultSet, boolean queryIsSelectOnly, Field metadataFromCache[], boolean isBatch)
        throws SQLException
    {
        ConnectionImpl locallyScopedConnection;
        resetCancelledState();
        locallyScopedConnection = connection;
        numberOfExecutions++;
        if(!doPingInstead)
            break MISSING_BLOCK_LABEL_36;
        doPingInstead();
        return results;
        StatementImpl.CancelTask timeoutTask = null;
        ResultSetInternalMethods rs;
        if(locallyScopedConnection.getEnableQueryTimeouts() && timeoutInMillis != 0 && locallyScopedConnection.versionMeetsMinimum(5, 0, 0))
        {
            timeoutTask = new StatementImpl.CancelTask(this, this);
	    //连接定时任务执行器Timer，等待timeoutInMillis毫秒后，执行查询定时任务timeoutTask
            ConnectionImpl.getCancelTimer().schedule(timeoutTask, timeoutInMillis);
        }
	//执行查询，并返回结果集
        rs = locallyScopedConnection.execSQL(this, null, maxRowsToRetrieve, sendPacket, resultSetType, resultSetConcurrency, createStreamingResultSet, currentCatalog, metadataFromCache, isBatch);
        if(timeoutTask != null)
        {
            timeoutTask.cancel();
            if(timeoutTask.caughtWhileCancelling != null)
                throw timeoutTask.caughtWhileCancelling;
            timeoutTask = null;
        }
        synchronized(cancelTimeoutMutex)
        {
            if(wasCancelled)
            {
                SQLException cause = null;
                if(wasCancelledByTimeout)
                    cause = new MySQLTimeoutException();
                else
                    cause = new MySQLStatementCancelledException();
                resetCancelledState();
                throw cause;
            }
        }
        if(timeoutTask != null)
            timeoutTask.cancel();
        break MISSING_BLOCK_LABEL_242;
        Exception exception1;
        exception1;
        if(timeoutTask != null)
            timeoutTask.cancel();
        throw exception1;
        return rs;
        NullPointerException npe;
        npe;
        checkClosed();
        throw npe;
    }

我们来看一下这一段都做了些什么？

if(locallyScopedConnection.getEnableQueryTimeouts() && timeoutInMillis != 0 && locallyScopedConnection.versionMeetsMinimum(5, 0, 0))
{
       timeoutTask = new StatementImpl.CancelTask(this, this);
       //连接定时任务执行器Timer，等待timeoutInMillis毫秒后，执行查询定时任务timeoutTask
        ConnectionImpl.getCancelTimer().schedule(timeoutTask, timeoutInMillis);
}

//StatementImpl

public class StatementImpl
    implements com.mysql.jdbc.Statement
{
    class CancelTask extends TimerTask
    {

        public void run()
        {
            Thread cancelThread = new Thread() {

                public void run()
                {
                    com.mysql.jdbc.Connection cancelConn = null;
                    Statement cancelStmt = null;
                    try
                    {
                        synchronized(cancelTimeoutMutex)
                        {
			    //复制connection
                            cancelConn = connection.duplicate();
			    //创建Statement
                            cancelStmt = cancelConn.createStatement();
                            cancelStmt.execute("KILL QUERY " + connectionId);
                            toCancel.wasCancelled = true;
                            toCancel.wasCancelledByTimeout = true;
                        }
                    }
                    catch(SQLException sqlEx)
                    {
                        caughtWhileCancelling = sqlEx;
                    }
                    catch(NullPointerException npe) { }
                    finally
                    {
                        if(cancelStmt != null)
                            try
                            {
                                cancelStmt.close();
                            }
                            catch(SQLException sqlEx)
                            {
                                throw new RuntimeException(sqlEx.toString());
                            }
                        if(cancelConn != null)
                            try
                            {
                                cancelConn.close();
                            }
                            catch(SQLException sqlEx)
                            {
                                throw new RuntimeException(sqlEx.toString());
                            }
                    }
                }

            };
            cancelThread.start();
        }

        long connectionId;
        SQLException caughtWhileCancelling;
        StatementImpl toCancel;


        CancelTask(StatementImpl cancellee)
            throws SQLException
        {
            connectionId = 0L;
            caughtWhileCancelling = null;
            connectionId = connection.getIO().getThreadId();
            toCancel = cancellee;
        }
    }
}

//创建Statement

cancelStmt = cancelConn.createStatement();

//ConnectionImpl

public Statement createStatement()
        throws SQLException
    {
        return createStatement(1003, 1007);
    }
public Statement createStatement(int resultSetType, int resultSetConcurrency)
        throws SQLException
    {
        checkClosed();
        StatementImpl stmt = new StatementImpl(this, database);
        stmt.setResultSetType(resultSetType);
        stmt.setResultSetConcurrency(resultSetConcurrency);
        return stmt;
    }
 //连接定时任务执行器Timer，等待timeoutInMillis毫秒后，执行查询定时任务timeoutTask
ConnectionImpl.getCancelTimer().schedule(timeoutTask, timeoutInMillis);
//ConnectionImpl
  protected static Timer getCancelTimer()
    {
        //private static Timer cancelTimer;
        return cancelTimer;
    }

从上面这一段可以看出，如果延时查询的话，就创建StatementImpl.CancelTask（TimeTask）定时任务，
并有ConnectionImpl的cancelTimer（Timer）去调度。

回到executeInternal方法，
来看执行查询，返回结果集，这个时调用ConnectionImpl的execSQL
//ConnectionImpl

ResultSetInternalMethods execSQL(StatementImpl callingStatement, String sql, int maxRows, Buffer packet, int resultSetType, int resultSetConcurrency, boolean streamResults, 
            String catalog, Field cachedMetadata[], boolean isBatch)
        throws SQLException
    {
        Object obj = mutex;
        JVM INSTR monitorenter ;
        long queryStartTime;
        int endOfQueryPacketPosition;
        queryStartTime = 0L;
        endOfQueryPacketPosition = 0;
        if(packet != null)
            endOfQueryPacketPosition = packet.getPosition();
        if(getGatherPerformanceMetrics())
            queryStartTime = System.currentTimeMillis();
        lastQueryFinishedTime = 0L;
        if(!failedOver || !autoCommit || isBatch || !shouldFallBack() || executingFailoverReconnect)
            break MISSING_BLOCK_LABEL_151;
        executingFailoverReconnect = true;
	//创建MysqlIO，这个我们在前面ServerPrepareStatement中讲过
        createNewIO(true);
        String connectedHost = io.getHost();
        if(connectedHost != null && hostList.get(0).equals(connectedHost))
        {
            failedOver = false;
            queriesIssuedFailedOver = 0L;
            setReadOnlyInternal(false);
        }
        if((getHighAvailability() || failedOver) && (autoCommit || getAutoReconnectForPools()) && needsPing && !isBatch)
            try
            {
                pingInternal(false, 0);
                needsPing = false;
            }
            catch(Exception Ex)
            {
                createNewIO(true);
            }
        ResultSetInternalMethods resultsetinternalmethods1;
        if(packet != null)
            break MISSING_BLOCK_LABEL_267;
        String encoding = null;
        if(getUseUnicode())
            encoding = getEncoding();
	//关键在这一句MysqlIO执行查询
        resultsetinternalmethods1 = io.sqlQueryDirect(callingStatement, sql, encoding, null, maxRows, resultSetType, resultSetConcurrency, streamResults, catalog, cachedMetadata);
        return resultsetinternalmethods1;
        ResultSetInternalMethods resultsetinternalmethods;
        try
        {
            resultsetinternalmethods = io.sqlQueryDirect(callingStatement, null, null, packet, maxRows, resultSetType, resultSetConcurrency, streamResults, catalog, cachedMetadata);
        }
        return resultsetinternalmethods;
    }

来看MysqlIO执行查询
//MysqlIO

final ResultSetInternalMethods sqlQueryDirect(StatementImpl callingStatement, String query, String characterEncoding, Buffer queryPacket, int maxRows, int resultSetType, int resultSetConcurrency, 
            boolean streamResults, String catalog, Field cachedMetadata[])
        throws Exception
    {
        statementExecutionDepth++;
	//返回结果集
        ResultSetInternalMethods resultsetinternalmethods;
        if(statementInterceptors == null)
            break MISSING_BLOCK_LABEL_47;
	//拦截器处理
        ResultSetInternalMethods interceptedResults = invokeStatementInterceptorsPre(query, callingStatement);
        if(interceptedResults == null)
            break MISSING_BLOCK_LABEL_47;
        resultsetinternalmethods = interceptedResults;
        statementExecutionDepth--;
        return resultsetinternalmethods;
        ResultSetInternalMethods resultsetinternalmethods1;
        long queryStartTime = 0L;
        long queryEndTime = 0L;
        if(query != null)
        {
            int packLength = 5 + query.length() * 2 + 2;
            String statementComment = connection.getStatementComment();
            byte commentAsBytes[] = null;
            if(statementComment != null)
            {
                commentAsBytes = StringUtils.getBytes(statementComment, null, characterEncoding, connection.getServerCharacterEncoding(), connection.parserKnowsUnicode(), getExceptionInterceptor());
                packLength += commentAsBytes.length;
                packLength += 6;
            }
            if(sendPacket == null)
                sendPacket = new Buffer(packLength);
            else
                sendPacket.clear();
            sendPacket.writeByte((byte)3);
            if(commentAsBytes != null)
            {
	        //将注释添加的查询包中
                sendPacket.writeBytesNoNull(Constants.SLASH_STAR_SPACE_AS_BYTES);
                sendPacket.writeBytesNoNull(commentAsBytes);
                sendPacket.writeBytesNoNull(Constants.SPACE_STAR_SLASH_SPACE_AS_BYTES);
            }
            if(characterEncoding != null)
            {
	        //如果有编码信息，则将查询编码后，组装到包中
                if(platformDbCharsetMatches)
                    sendPacket.writeStringNoNull(query, characterEncoding, connection.getServerCharacterEncoding(), connection.parserKnowsUnicode(), connection);
                else
                if(StringUtils.startsWithIgnoreCaseAndWs(query, "LOAD DATA"))
                    sendPacket.writeBytesNoNull(query.getBytes());
                else
                    sendPacket.writeStringNoNull(query, characterEncoding, connection.getServerCharacterEncoding(), connection.parserKnowsUnicode(), connection);
            } else
            {
                sendPacket.writeStringNoNull(query);
            }
            queryPacket = sendPacket;
        }
        byte queryBuf[] = null;
        int oldPacketPosition = 0;
        if(needToGrabQueryFromPacket)
        {
            queryBuf = queryPacket.getByteBuffer();
            oldPacketPosition = queryPacket.getPosition();
            queryStartTime = getCurrentTimeNanosOrMillis();
        }
        if(autoGenerateTestcaseScript)
        {
            String testcaseQuery = null;
            if(query != null)
                testcaseQuery = query;
            else
                testcaseQuery = new String(queryBuf, 5, oldPacketPosition - 5);
            StringBuffer debugBuf = new StringBuffer(testcaseQuery.length() + 32);
            connection.generateConnectionCommentBlock(debugBuf);
            debugBuf.append(testcaseQuery);
            debugBuf.append(';');
            connection.dumpTestcaseQuery(debugBuf.toString());
        }
	//MysqlIO发送查询包到Server，获取返回结果
        Buffer resultPacket = sendCommand(3, null, queryPacket, false, null, 0);
        long fetchBeginTime = 0L;
        long fetchEndTime = 0L;
        String profileQueryToLog = null;
        boolean queryWasSlow = false;
        if(profileSql || logSlowQueries)
        {
            queryEndTime = System.currentTimeMillis();
            boolean shouldExtractQuery = false;
            if(profileSql)
                shouldExtractQuery = true;
            else
            if(logSlowQueries)
            {
                long queryTime = queryEndTime - queryStartTime;
                boolean logSlow = false;
                if(useAutoSlowLog)
                {
                    logSlow = queryTime > (long)connection.getSlowQueryThresholdMillis();
                } else
                {
                    logSlow = connection.isAbonormallyLongQuery(queryTime);
                    connection.reportQueryTime(queryTime);
                }
                if(logSlow)
                {
                    shouldExtractQuery = true;
                    queryWasSlow = true;
                }
            }
            if(shouldExtractQuery)
            {
                boolean truncated = false;
                int extractPosition = oldPacketPosition;
                if(oldPacketPosition > connection.getMaxQuerySizeToLog())
                {
                    extractPosition = connection.getMaxQuerySizeToLog() + 5;
                    truncated = true;
                }
                profileQueryToLog = new String(queryBuf, 5, extractPosition - 5);
                if(truncated)
                    profileQueryToLog = profileQueryToLog + Messages.getString("MysqlIO.25");
            }
            fetchBeginTime = queryEndTime;
        }
	//从中resultPacket，获取返回结果
        ResultSetInternalMethods rs = readAllResults(callingStatement, maxRows, resultSetType, resultSetConcurrency, streamResults, catalog, resultPacket, false, -1L, cachedMetadata);
        if(queryWasSlow && !serverQueryWasSlow)
        {
            StringBuffer mesgBuf = new StringBuffer(48 + profileQueryToLog.length());
            mesgBuf.append(Messages.getString("MysqlIO.SlowQuery", new Object[] {
                new Long(slowQueryThreshold), queryTimingUnits, new Long(queryEndTime - queryStartTime)
            }));
            mesgBuf.append(profileQueryToLog);
            ProfilerEventHandler eventSink = ProfilerEventHandlerFactory.getInstance(connection);
            eventSink.consumeEvent(new ProfilerEvent((byte)6, "", catalog, connection.getId(), callingStatement == null ? 999 : callingStatement.getId(), ((ResultSetImpl)rs).resultId, System.currentTimeMillis(), (int)(queryEndTime - queryStartTime), queryTimingUnits, null, new Throwable(), mesgBuf.toString()));
            if(connection.getExplainSlowQueries())
                if(oldPacketPosition < 1048576)
                    explainSlowQuery(queryPacket.getBytes(5, oldPacketPosition - 5), profileQueryToLog);
                else
                    connection.getLog().logWarn(Messages.getString("MysqlIO.28") + 1048576 + Messages.getString("MysqlIO.29"));
        }
        if(logSlowQueries)
        {
            ProfilerEventHandler eventSink = ProfilerEventHandlerFactory.getInstance(connection);
            if(queryBadIndexUsed)
                eventSink.consumeEvent(new ProfilerEvent((byte)6, "", catalog, connection.getId(), callingStatement == null ? 999 : callingStatement.getId(), ((ResultSetImpl)rs).resultId, System.currentTimeMillis(), queryEndTime - queryStartTime, queryTimingUnits, null, new Throwable(), Messages.getString("MysqlIO.33") + profileQueryToLog));
            if(queryNoIndexUsed)
                eventSink.consumeEvent(new ProfilerEvent((byte)6, "", catalog, connection.getId(), callingStatement == null ? 999 : callingStatement.getId(), ((ResultSetImpl)rs).resultId, System.currentTimeMillis(), queryEndTime - queryStartTime, queryTimingUnits, null, new Throwable(), Messages.getString("MysqlIO.35") + profileQueryToLog));
            if(serverQueryWasSlow)
                eventSink.consumeEvent(new ProfilerEvent((byte)6, "", catalog, connection.getId(), callingStatement == null ? 999 : callingStatement.getId(), ((ResultSetImpl)rs).resultId, System.currentTimeMillis(), queryEndTime - queryStartTime, queryTimingUnits, null, new Throwable(), Messages.getString("MysqlIO.ServerSlowQuery") + profileQueryToLog));
        }
        if(profileSql)
        {
            fetchEndTime = getCurrentTimeNanosOrMillis();
            ProfilerEventHandler eventSink = ProfilerEventHandlerFactory.getInstance(connection);
            eventSink.consumeEvent(new ProfilerEvent((byte)3, "", catalog, connection.getId(), callingStatement == null ? 999 : callingStatement.getId(), ((ResultSetImpl)rs).resultId, System.currentTimeMillis(), queryEndTime - queryStartTime, queryTimingUnits, null, new Throwable(), profileQueryToLog));
            eventSink.consumeEvent(new ProfilerEvent((byte)5, "", catalog, connection.getId(), callingStatement == null ? 999 : callingStatement.getId(), ((ResultSetImpl)rs).resultId, System.currentTimeMillis(), fetchEndTime - fetchBeginTime, queryTimingUnits, null, new Throwable(), null));
        }
        if(hadWarnings)
            scanForAndThrowDataTruncation();
        if(statementInterceptors != null)
        {
            ResultSetInternalMethods interceptedResults = invokeStatementInterceptorsPost(query, callingStatement, rs);
            if(interceptedResults != null)
                rs = interceptedResults;
        }
        resultsetinternalmethods1 = rs;
        statementExecutionDepth--;
        return resultsetinternalmethods1;  
}
//从缓冲区，去除结果集
ResultSetImpl readAllResults(StatementImpl callingStatement, int maxRows, int resultSetType, int resultSetConcurrency, boolean streamResults, String catalog, Buffer resultPacket, 
            boolean isBinaryEncoded, long preSentColumnCount, Field metadataFromCache[])
        throws SQLException
    {
        resultPacket.setPosition(resultPacket.getPosition() - 1);
        ResultSetImpl topLevelResultSet = readResultsForQueryOrUpdate(callingStatement, maxRows, resultSetType, resultSetConcurrency, streamResults, catalog, resultPacket, isBinaryEncoded, preSentColumnCount, metadataFromCache);
        ResultSetImpl currentResultSet = topLevelResultSet;
        boolean checkForMoreResults = (clientParam & 131072L) != 0L;
        boolean serverHasMoreResults = (serverStatus & 8) != 0;
        if(serverHasMoreResults && streamResults)
        {
            if(topLevelResultSet.getUpdateCount() != -1L)
                tackOnMoreStreamingResults(topLevelResultSet);
            reclaimLargeReusablePacket();
            return topLevelResultSet;
        }
        for(boolean moreRowSetsExist = checkForMoreResults & serverHasMoreResults; moreRowSetsExist; moreRowSetsExist = (serverStatus & 8) != 0)
        {
            Buffer fieldPacket = checkErrorPacket();
            fieldPacket.setPosition(0);
	    //读取结果集
            ResultSetImpl newResultSet = readResultsForQueryOrUpdate(callingStatement, maxRows, resultSetType, resultSetConcurrency, streamResults, catalog, fieldPacket, isBinaryEncoded, preSentColumnCount, metadataFromCache);
            currentResultSet.setNextResultSet(newResultSet);
            currentResultSet = newResultSet;
        }

        if(!streamResults)
            clearInputStream();
        reclaimLargeReusablePacket();
        return topLevelResultSet;
    }

从上面可以看出，批处理就是将PrepareStatment的参数信息，是不是流，是否为null，参数值，参数流封装成BatchParams，添加到batchedArgs List中，执行批处理是将batchedArgs里的参数分批次通过MysqlIO发送给Server。

//清空批信息

public synchronized void clearBatch()
        throws SQLException
    {
        batchHasPlainStatements = false;
        super.clearBatch();
    }
 //StatementImpl
  public synchronized void clearBatch()
        throws SQLException
    {
        if(batchedArgs != null)
	    //清空参数List
            batchedArgs.clear();
    }

   //清除参数
    public synchronized void clearParameters()
        throws SQLException
    {
        checkClosed();
        for(int i = 0; i < parameterValues.length; i++)
        {
	   //重置statement，参数值，参数流，参数类型，是否为null，是否是流描述信息
            parameterValues[i] = null;
            parameterStreams[i] = null;
            isStream[i] = false;
            isNull[i] = false;
            parameterTypes[i] = 0;
        }

    }
    //关闭Statement
    public synchronized void close()
        throws SQLException
    {
        //委托给realClose
        realClose(true, true);
    }
    //关闭Statement
     protected void realClose(boolean calledExplicitly, boolean closeOpenResults)
        throws SQLException
    {
        if(useUsageAdvisor && numberOfExecutions <= 1)
        {
            String message = Messages.getString("PreparedStatement.43");
            eventSink.consumeEvent(new ProfilerEvent((byte)0, "", currentCatalog, connectionId, getId(), -1, System.currentTimeMillis(), 0L, Constants.MILLIS_I18N, null, pointOfOrigin, message));
        }
        super.realClose(calledExplicitly, closeOpenResults);
        dbmd = null;
        originalSql = null;
        staticSqlStrings = (byte[][])null;
        parameterValues = (byte[][])null;
        parameterStreams = null;
        isStream = null;
        streamLengths = null;
        isNull = null;
        streamConvertBuf = null;
        parameterTypes = null;
    }

从realClose方法来看，关闭Statement，就是清空参数类型，参数流，参数值，sql，databaseMetaData等信息。