<?php
 
/**
* 实现数据库的主从分离，该类会维护多个数据库的配置：一个主数据库配置，多个从数据库的配置。
* 具体使用主数据库还是从数据库，使用如下规则：
* 1、CDbCommandExt的prepare方法会根据sql语句是读还是写，来调用CDbConnectionExt的getPdoInstance方法，来获取主数据库或者从数据库链接，默认使用主数据库
* 2、如果当前处于一个事务中，那么无视第一条规则，在事务结束前全部使用主数据库
* 3、如果从数据库的配置为空，则使用主数据库
*/
class CDbConnectionExt extends CDbConnection
{
/**
* @var string The Data Source Name, or DSN, contains the information required to connect to the database.
* @see http://www.php.net/m...O-construct.php
*/
public $connectionString;
/**
* @var string the username for establishing DB connection. Defaults to empty string.
*/
public $username='';
/**
* @var string the password for establishing DB connection. Defaults to empty string.
*/
public $password='';
 
/**
* @var array 从数据库配置数组，例如：
* array(
* array('connectionString'=>'mysql:host=192.168.1.100;dbname=McAm;port=8001', 'username'=>'mcam', 'password'=>'123456'),
* array('connectionString'=>'mysql:host=192.168.1.101;dbname=McAm;port=8001', 'username'=>'mcam', 'password'=>'123456'),
* array('connectionString'=>'mysql:host=192.168.1.102;dbname=McAm;port=8001', 'username'=>'mcam', 'password'=>'123456'),
* )
*/
public $slaveConfig = array();
 
/**
* @var integer number of seconds that table metadata can remain valid in cache.
* Use 0 or negative value to indicate not caching schema.
* If greater than 0 and the primary cache is enabled, the table metadata will be cached.
* @see schemaCachingExclude
*/
public $schemaCachingDuration=0;
/**
* @var array list of tables whose metadata should NOT be cached. Defaults to empty array.
* @see schemaCachingDuration
*/
public $schemaCachingExclude=array();
/**
* @var string the ID of the cache application component that is used to cache the table metadata.
* Defaults to 'cache' which refers to the primary cache application component.
* Set this property to false if you want to disable caching table metadata.
* @since 1.0.10
*/
public $schemaCacheID='cache';
/**
* @var boolean whether the database connection should be automatically established
* the component is being initialized. Defaults to true. Note, this property is only
* effective when the CDbConnection object is used as an application component.
*/
public $autoConnect=true;
/**
* @var string the charset used for database connection. The property is only used
* for MySQL and PostgreSQL databases. Defaults to null, meaning using default charset
* as specified by the database.
*/
public $charset;
/**
* @var boolean whether to turn on prepare emulation. Defaults to false, meaning PDO
* will use the native prepare support if available. For some databases (such as MySQL),
* this may need to be set true so that PDO can emulate the prepare support to bypass
* the buggy native prepare support. Note, this property is only effective for PHP 5.1.3 or above.
*/
public $emulatePrepare=false;
/**
* @var boolean whether to log the values that are bound to a prepare SQL statement.
* Defaults to false. During development, you may consider setting this property to true
* so that parameter values bound to SQL statements are logged for debugging purpose.
* You should be aware that logging parameter values could be expensive and have significant
* impact on the performance of your application.
* @since 1.0.5
*/
public $enableParamLogging=false;
/**
* @var boolean whether to enable profiling the SQL statements being executed.
* Defaults to false. This should be mainly enabled and used during development
* to find out the bottleneck of SQL executions.
* @since 1.0.6
*/
public $enableProfiling=false;
/**
* @var string the default prefix for table names. Defaults to null, meaning no table prefix.
* By setting this property, any token like '{{tableName}}' in {@link CDbCommand::text} will
* be replaced by 'prefixTableName', where 'prefix' refers to this property value.
* @since 1.1.0
*/
public $tablePrefix;
/**
* @var array list of SQL statements that should be executed right after the DB connection is established.
* @since 1.1.1
*/
public $initSQLs;
 
private $_attributes=array();
private $_active=false;
private $_pdo;
private $_transaction;
private $_schema;
 
//主数据库、从数据库链接
private $_pdoMaster = null;
private $_pdoSlave = null;
 
/**
* Constructor.
* Note, the DB connection is not established when this connection
* instance is created. Set {@link setActive active} property to true
* to establish the connection.
* @param string The Data Source Name, or DSN, contains the information required to connect to the database.
* @param string The user name for the DSN string.
* @param string The password for the DSN string.
* @see http://www.php.net/m...O-construct.php
*/
public function __construct($dsn='',$username='',$password='',$slaveConfig=array())
{
$this->connectionString=$dsn;
$this->username=$username;
$this->password=$password;
 
//设置从数据库配置
$this->slaveConfig=$slaveConfig;
 
}
 
/**
* Close the connection when serializing.
*/
public function __sleep()
{
$this->close();
return array_keys(get_object_vars($this));
}
 
/**
* @return array list of available PDO drivers
* @see http://www.php.net/m...ableDrivers.php
*/
public static function getAvailableDrivers()
{
return PDO::getAvailableDrivers();
}
 
/**
* Initializes the component.
* This method is required by {@link IApplicationComponent} and is invoked by application
* when the CDbConnection is used as an application component.
* If you override this method, make sure to call the parent implementation
* so that the component can be marked as initialized.
*/
public function init()
{
parent::init();
if($this->autoConnect)
$this->setActive(true);
}
 
/**
* @return boolean whether the DB connection is established
*/
public function getActive()
{
return $this->_active;
}
 
/**
* Open or close the DB connection.
* @param boolean whether to open or close DB connection
* @throws CException if connection fails
*/
public function setActive($value)
{
//不在这边创建数据库链接，在getPdoInstance方法中创建，即在真正需要的时候才创建
$this->_active=true;
/*if($value!=$this->_active)
{
if($value)
$this->open();
else
$this->close();
}*/
}
 
/**
* Opens DB connection if it is currently not
* @throws CException if connection fails
*/
protected function open($connectionString='', $username='', $password='')
{
//如果没有输入数据库配置，则使用主数据库配置
$connectionString = $connectionString?$connectionString:$this->connectionString;
$username = $username?$username:$this->username;
$password = $password?$password:$this->password;
 
if(empty($connectionString))
throw new CDbException(Yii::t('yii','CDbConnection.connectionString cannot be empty.'));
//本次创建出来的pdo链接
$pdo = null;
try
{
Yii::trace('Opening DB connection','system.db.CDbConnection');
$pdo=$this->createPdoInstance($connectionString, $username, $password);
$this->initConnection($pdo);
}
catch(PDOException $e)
{
if(YII_DEBUG)
{
throw new CDbException(Yii::t('yii','CDbConnection failed to open the DB connection: {error}',
array('{error}'=>$e->getMessage())));
}
else
{
Yii::log($e->getMessage(),CLogger::LEVEL_ERROR,'exception.CDbException');
throw new CDbException(Yii::t('yii','CDbConnection failed to open the DB connection.'));
}
}
//返回创建的pdo链接
return $pdo;
}
 
/**
* Closes the currently active DB connection.
* It does nothing if the connection is already closed.
*/
protected function close()
{
Yii::trace('Closing DB connection','system.db.CDbConnection');
$this->_pdo=null;
$this->_active=false;
$this->_schema=null;
 
//删除主数据库链接、从数据库链接
$this->_pdoMaster=null;
$this->_pdoSlave=null;
}
 
/**
* Creates the PDO instance.
* When some functionalities are missing in the pdo driver, we may use
* an adapter class to provides them.
* @return PDO the pdo instance
* @since 1.0.4
*/
protected function createPdoInstance($connectionString, $username, $password)
{
$pdoClass='PDO';
if(($pos=strpos($connectionString,':'))!==false)
{
$driver=strtolower(substr($this->connectionString,0,$pos));
if($driver==='mssql' || $driver==='dblib')
$pdoClass='CMssqlPdoAdapter';
}
return new $pdoClass($connectionString,$username,$password,$this->_attributes);
}
 
/**
* Initializes the open db connection.
* This method is invoked right after the db connection is established.
* The default implementation is to set the charset for MySQL and PostgreSQL database connections.
* @param PDO the PDO instance
*/
protected function initConnection($pdo)
{
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
if($this->emulatePrepare && constant('PDO::ATTR_EMULATE_PREPARES'))
$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES,true);
if($this->charset!==null)
{
if(strcasecmp($pdo->getAttribute(PDO::ATTR_DRIVER_NAME),'sqlite'))
$pdo->exec('SET NAMES '.$pdo->quote($this->charset));
}
if($this->initSQLs!==null)
{
foreach($this->initSQLs as $sql)
$pdo->exec($sql);
}
}
 
/**
* 真正的创建pdo链接
* @return PDO the PDO instance, null if the connection is not established yet
*/
public function getPdoInstance($useSlave=false)
{
//满足这两种情况才使用从库：1、存在从库；2、当前不处于一个事务中
if( $useSlave &&
count($this->slaveConfig) &&
(!$this->_transaction || !$this->_transaction->getActive()))
{
if($this->_pdoSlave)
$this->_pdo = $this->_pdoSlave;
else
{
//随机选择一个从库
$randIndex = array_rand($this->slaveConfig);
extract($this->slaveConfig[$randIndex]);
$this->_pdo = $this->_pdoSlave = $this->open($connectionString, $username, $password);
}
}
else{
if($this->_pdoMaster)
$this->_pdo = $this->_pdoMaster;
else
//创建主数据库链接
$this->_pdo = $this->_pdoMaster = $this->open();
}
return $this->_pdo;
}
 
/**
* Creates a command for execution.
* @param string SQL statement associated with the new command.
* @return CDbCommand the DB command
* @throws CException if the connection is not active
*/
public function createCommand($sql)
{
if($this->getActive()){
//需要使用CDbCommandExt类，因为该类可以获得sql的读写状态，从而可以选择主从数据库
return new CDbCommandExt($this,$sql);
//return new CDbCommand($this,$sql);
}
else
throw new CDbException(Yii::t('yii','CDbConnection is inactive and cannot perform any DB operations.'));
}
 
/**
* @return CDbTransaction the currently active transaction. Null if no active transaction.
*/
public function getCurrentTransaction()
{
if($this->_transaction!==null)
{
if($this->_transaction->getActive())
return $this->_transaction;
}
return null;
}
 
/**
* Starts a transaction.
* @return CDbTransaction the transaction initiated
* @throws CException if the connection is not active
*/
public function beginTransaction()
{
if($this->getActive())
{
//获得主数据库，将当前的pdo链接设置为主数据库
$this->_pdo = $this->getPdoInstance();
 
if($this->_pdo){
$this->_pdo->beginTransaction();
return $this->_transaction = new CDbTransaction($this);
}
else
throw new CDbException(Yii::t('yii','CDbConnection is inactive and cannot perform any DB operations.'));
}
else
throw new CDbException(Yii::t('yii','CDbConnection is inactive and cannot perform any DB operations.'));
}
 
/**
* @return CDbSchema the database schema for the current connection
* @throws CException if the connection is not active yet
*/
public function getSchema()
{
if($this->_schema!==null)
return $this->_schema;
else
{
if(!$this->getActive())
throw new CDbException(Yii::t('yii','CDbConnection is inactive and cannot perform any DB operations.'));
$driver=$this->getDriverName();
switch(strtolower($driver))
{
case 'pgsql': // PostgreSQL
return $this->_schema=new CPgsqlSchema($this);
case 'mysqli': // MySQL
case 'mysql':
return $this->_schema=new CMysqlSchema($this);
case 'sqlite': // sqlite 3
case 'sqlite2': // sqlite 2
return $this->_schema=new CSqliteSchema($this);
case 'mssql': // Mssql driver on windows hosts
case 'dblib': // dblib drivers on linux (and maybe others os) hosts
return $this->_schema=new CMssqlSchema($this);
case 'oci': // Oracle driver
return $this->_schema=new COciSchema($this);
case 'ibm':
default:
throw new CDbException(Yii::t('yii','CDbConnection does not support reading schema for {driver} database.',
array('{driver}'=>$driver)));
}
}
}
 
/**
* Returns the SQL command builder for the current DB connection.
* @return CDbCommandBuilder the command builder
* @since 1.0.4
*/
public function getCommandBuilder()
{
return $this->getSchema()->getCommandBuilder();
}
 
/**
* Returns the ID of the last inserted row or sequence value.
* @param string name of the sequence object (required by some DBMS)
* @return string the row ID of the last row inserted, or the last value retrieved from the sequence object
* @see http://www.php.net/m...astInsertId.php
*/
public function getLastInsertID($sequenceName='')
{
//必须使用主数据库链接
if($this->getActive() && $this->_pdoMaster)
//return $this->_pdo->lastInsertId($sequenceName);
return $this->_pdoMaster->lastInsertId($sequenceName);
else
throw new CDbException(Yii::t('yii','CDbConnection is inactive and cannot perform any DB operations.'));
}
 
/**
* Quotes a string value for use in a query.
* @param string string to be quoted
* @return string the properly quoted string
* @see http://www.php.net/m...n.PDO-quote.php
*/
public function quoteValue($str)
{
if($this->getActive()){
//如果当前链接不存在，则创建一个与从数据库之间的链接
if(!$this->_pdo)
$this->_pdo = $this->getPdoInstance(true);
 
//如果创建链接失败，抛出异常
if(!$this->_pdo)
throw new CDbException(Yii::t('yii','CDbConnection is inactive and cannot perform any DB operations.'));
 
return $this->_pdo->quote($str);
}
else
throw new CDbException(Yii::t('yii','CDbConnection is inactive and cannot perform any DB operations.'));
}
 
/**
* Quotes a table name for use in a query.
* @param string table name
* @return string the properly quoted table name
*/
public function quoteTableName($name)
{
return $this->getSchema()->quoteTableName($name);
}
 
/**
* Quotes a column name for use in a query.
* @param string column name
* @return string the properly quoted column name
*/
public function quoteColumnName($name)
{
return $this->getSchema()->quoteColumnName($name);
}
 
/**
* Determines the PDO type for the specified PHP type.
* @param string The PHP type (obtained by gettype() call).
* @return integer the corresponding PDO type
*/
public function getPdoType($type)
{
static $map=array
(
'boolean'=>PDO::PARAM_BOOL,
'integer'=>PDO::PARAM_INT,
'string'=>PDO::PARAM_STR,
'NULL'=>PDO::PARAM_NULL,
);
return isset($map[$type]) ? $map[$type] : PDO::PARAM_STR;
}
 
/**
* @return mixed the case of the column names
* @see http://www.php.net/m...etattribute.php
*/
public function getColumnCase()
{
return $this->getAttribute(PDO::ATTR_CASE);
}
 
/**
* @param mixed the case of the column names
* @see http://www.php.net/m...etattribute.php
*/
public function setColumnCase($value)
{
$this->setAttribute(PDO::ATTR_CASE,$value);
}
 
/**
* @return mixed how the null and empty strings are converted
* @see http://www.php.net/m...etattribute.php
*/
public function getNullConversion()
{
return $this->getAttribute(PDO::ATTR_ORACLE_NULLS);
}
 
/**
* @param mixed how the null and empty strings are converted
* @see http://www.php.net/m...etattribute.php
*/
public function setNullConversion($value)
{
$this->setAttribute(PDO::ATTR_ORACLE_NULLS,$value);
}
 
/**
* @return boolean whether creating or updating a DB record will be automatically committed.
* Some DBMS (such as sqlite) may not support this feature.
*/
public function getAutoCommit()
{
return $this->getAttribute(PDO::ATTR_AUTOCOMMIT);
}
 
/**
* @param boolean whether creating or updating a DB record will be automatically committed.
* Some DBMS (such as sqlite) may not support this feature.
*/
public function setAutoCommit($value)
{
$this->setAttribute(PDO::ATTR_AUTOCOMMIT,$value);
}
 
/**
* @return boolean whether the connection is persistent or not
* Some DBMS (such as sqlite) may not support this feature.
*/
public function getPersistent()
{
return $this->getAttribute(PDO::ATTR_PERSISTENT);
}
 
/**
* @param boolean whether the connection is persistent or not
* Some DBMS (such as sqlite) may not support this feature.
*/
public function setPersistent($value)
{
return $this->setAttribute(PDO::ATTR_PERSISTENT,$value);
}
 
/**
* @return string name of the DB driver
*/
public function getDriverName()
{
return $this->getAttribute(PDO::ATTR_DRIVER_NAME);
}
 
/**
* @return string the version information of the DB driver
*/
public function getClientVersion()
{
return $this->getAttribute(PDO::ATTR_CLIENT_VERSION);
}
 
/**
* @return string the status of the connection
* Some DBMS (such as sqlite) may not support this feature.
*/
public function getConnectionStatus()
{
return $this->getAttribute(PDO::ATTR_CONNECTION_STATUS);
}
 
/**
* @return boolean whether the connection performs data prefetching
*/
public function getPrefetch()
{
return $this->getAttribute(PDO::ATTR_PREFETCH);
}
 
/**
* @return string the information of DBMS server
*/
public function getServerInfo()
{
return $this->getAttribute(PDO::ATTR_SERVER_INFO);
}
 
/**
* @return string the version information of DBMS server
*/
public function getServerVersion()
{
return $this->getAttribute(PDO::ATTR_SERVER_VERSION);
}
 
/**
* @return int timeout settings for the connection
*/
public function getTimeout()
{
return $this->getAttribute(PDO::ATTR_TIMEOUT);
}
 
/**
* Obtains a specific DB connection attribute information.
* @param int the attribute to be queried
* @return mixed the corresponding attribute information
* @see http://www.php.net/m...etAttribute.php
*/
public function getAttribute($name)
{
if($this->getActive()){
//如果当前链接不存在，则创建一个与从数据库之间的链接
if(!$this->_pdo)
$this->_pdo = $this->getPdoInstance(true);
 
//如果创建链接失败，抛出异常
if(!$this->_pdo)
throw new CDbException(Yii::t('yii','CDbConnection is inactive and cannot perform any DB operations.'));
 
return $this->_pdo->getAttribute($name);
}
else
throw new CDbException(Yii::t('yii','CDbConnection is inactive and cannot perform any DB operations.'));
}
 
/**
* Sets an attribute on the database connection.
* @param int the attribute to be set
* @param mixed the attribute value
* @see http://www.php.net/m...etAttribute.php
*/
public function setAttribute($name,$value)
{
if($this->_pdo instanceof PDO)
$this->_pdo->setAttribute($name,$value);
/*else
$this->_attributes[$name]=$value;*/
//记录设置数据库属性，在主库与从库之间切换时，数据库属性需要从新设置
$this->_attributes[$name]=$value;
}
 
/**
* Returns the statistical results of SQL executions.
* The results returned include the number of SQL statements executed and
* the total time spent.
* In order to use this method, {@link enableProfiling} has to be set true.
* @return array the first element indicates the number of SQL statements executed,
* and the second element the total time spent in SQL execution.
* @since 1.0.6
*/
public function getStats()
{
$logger=Yii::getLogger();
$timings=$logger->getProfilingResults(null,'system.db.CDbCommand.query');
$count=count($timings);
$time=array_sum($timings);
$timings=$logger->getProfilingResults(null,'system.db.CDbCommand.execute');
$count+=count($timings);
$time+=array_sum($timings);
return array($count,$time);
}
}

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