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db_driver.html
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<!DOCTYPE html>
<!--[if lt IE 7]> <html class="no-js lt-ie9 lt-ie8 lt-ie7"> <![endif]-->
<!--[if IE 7]> <html class="no-js lt-ie9 lt-ie8"> <![endif]-->
<!--[if IE 8]> <html class="no-js lt-ie9"> <![endif]-->
<!--[if gt IE 8]><!--> <html class="no-js"> <!--<![endif]-->
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title></title>
<meta name="description" content="">
<meta name="viewport" content="width=device-width, initial-scale=1">
<!-- Place favicon.ico and apple-touch-icon.png in the root directory -->
<link rel="stylesheet" href="css/normalize.css">
<link rel="stylesheet" href="css/main.css">
<script src="js/vendor/modernizr-2.6.2.min.js"></script>
<link rel="stylesheet" href="css/bootstrap.css">
<link rel="stylesheet" href="css/shCore.css">
<link rel="stylesheet" href="css/shThemeDefault.css">
<script src="js/shCore.js"></script>
<script src="js/shBrushPhp.js"></script>
</head>
<body>
<!--[if lt IE 7]>
<p class="browsehappy">You are using an <strong>outdated</strong> browser. Please <a href="http://browsehappy.com/">upgrade your browser</a> to improve your experience.</p>
<![endif]-->
<!-- Add your site or application content here -->
<div class='alert alert-success'>
我們開始分析database/DB_driver.php。<br/>
</div>
<!-- You also need to add some content to highlight, but that is covered elsewhere. -->
<pre class="brush: php">
/**
* CodeIgniter
*
* An open source application development framework for PHP 5.1.6 or newer
*
* @package CodeIgniter
* @author ExpressionEngine Dev Team
* @copyright Copyright (c) 2008 - 2011, EllisLab, Inc.
* @license http://codeigniter.com/user_guide/license.html
* @link http://codeigniter.com
* @since Version 1.0
* @filesource
*/
// ------------------------------------------------------------------------
/**
* Database Driver Class
*
* This is the platform-independent base DB implementation class.
* This class will not be called directly. Rather, the adapter
* class for the specific database will extend and instantiate it.
*
* @package CodeIgniter
* @subpackage Drivers
* @category Database
* @author ExpressionEngine Dev Team
* @link http://codeigniter.com/user_guide/database/
*/
class CI_DB_driver {
var $username;
var $password;
var $hostname;
var $database;
var $dbdriver = 'mysql';
var $dbprefix = '';
var $char_set = 'utf8';
var $dbcollat = 'utf8_general_ci';
var $autoinit = TRUE; // Whether to automatically initialize the DB
var $swap_pre = '';
var $port = '';
var $pconnect = FALSE;
var $conn_id = FALSE;
var $result_id = FALSE;
var $db_debug = FALSE;
var $benchmark = 0;
var $query_count = 0;
var $bind_marker = '?';
var $save_queries = TRUE;
var $queries = array();
var $query_times = array();
var $data_cache = array();
var $trans_enabled = TRUE;
var $trans_strict = TRUE;
var $_trans_depth = 0;
var $_trans_status = TRUE; // Used with transactions to determine if a rollback should occur
var $cache_on = FALSE;
var $cachedir = '';
var $cache_autodel = FALSE;
var $CACHE; // The cache class object
// Private variables
var $_protect_identifiers = TRUE;
var $_reserved_identifiers = array('*'); // Identifiers that should NOT be escaped
// These are use with Oracle
var $stmt_id;
var $curs_id;
var $limit_used;
</pre>
<div class='alert alert-success'>
以底線開頭代表private變數。其實PHP有private可以宣告呀。<br/>
所以是很久以前寫的code嗎。
</div>
<pre class="brush: php">
/**
* Constructor. Accepts one parameter containing the database
* connection settings.
*
* @param array
*/
function __construct($params)
{
if (is_array($params))
{
foreach ($params as $key => $val)
{
$this->$key = $val;
}
}
log_message('debug', 'Database Driver Class Initialized');
}
</pre>
<div class='alert alert-success'>
傳入資料庫設定的陣列給建構式，它會將類別開頭那一大堆變數替換掉。<br/>
注意這個動態指定成員變數的技法。
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
/**
* Initialize Database Settings
*
* @access private Called by the constructor
* @param mixed
* @return void
*/
function initialize()
{
// If an existing connection resource is available
// there is no need to connect and select the database
if (is_resource($this->conn_id) OR is_object($this->conn_id))
{
return TRUE;
}
</pre>
<div class='alert alert-danger'>
正要開始初始化，哪會已經有連線存在？多餘的一段code。
</div>
<pre class="brush: php">
// ----------------------------------------------------------------
// Connect to the database and set the connection ID
$this->conn_id = ($this->pconnect == FALSE) ? $this->db_connect() : $this->db_pconnect();
// No connection resource? Throw an error
if ( ! $this->conn_id)
{
log_message('error', 'Unable to connect to the database');
if ($this->db_debug)
{
$this->display_error('db_unable_to_connect');
}
return FALSE;
}
</pre>
<div class='alert alert-success'>
pconnect的p是指persistent。第一行在決定要不要用persistent連線。<br/>
請參見：<br/>
<a href='http://php.net/manual/en/features.persistent-connections.php'>Persistent Database Connections</a><br/>
<a href='http://stackoverflow.com/questions/1830830/advantages-disadvantages-of-pconnect-option-in-codeigniter'>Advantages / Disadvantages of pconnect option in CodeIgniter</a>
</div>
<pre class="brush: php">
// ----------------------------------------------------------------
// Select the DB... assuming a database name is specified in the config file
if ($this->database != '')
{
if ( ! $this->db_select())
{
log_message('error', 'Unable to select database: '.$this->database);
if ($this->db_debug)
{
$this->display_error('db_unable_to_select', $this->database);
}
return FALSE;
}
else
{
// We've selected the DB. Now we set the character set
if ( ! $this->db_set_charset($this->char_set, $this->dbcollat))
{
return FALSE;
}
return TRUE;
}
}
</pre>
<div class='alert alert-success'>
若是autoinit為TRUE，而database卻沒有指定的話，邏輯上是會出錯的（詳見config檔）。<br/>
最外層那個if保護了這件事，讓暫時沒有使用database的application可以順利運作。<br/>
</div>
<div class='alert alert-danger'>
針對錯誤的處理有矛盾。無法連線資料庫會先display_error再return FALSE，無法設定字元卻是直接return FALSE、不報錯。<br/>
究竟要嚴厲，還是要寬容呢？應該要選一個。
</div>
<pre class="brush: php">
return TRUE;
}
</pre>
<div class='alert alert-success'>
註解寫這是給建構式呼叫的函數。結果建構式內沒呼叫他，是更外面在呼叫。<br/>
要連結資料庫時會呼叫這個函數。
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
/**
* Set client character set
*
* @access public
* @param string
* @param string
* @return resource
*/
function db_set_charset($charset, $collation)
{
if ( ! $this->_db_set_charset($this->char_set, $this->dbcollat))
{
log_message('error', 'Unable to set database connection charset: '.$this->char_set);
if ($this->db_debug)
{
$this->display_error('db_unable_to_set_charset', $this->char_set);
}
return FALSE;
}
return TRUE;
}
</pre>
<div class='alert alert-danger'>
上面的批評是個誤會。原來是在這裡處理報錯。
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
/**
* The name of the platform in use (mysql, mssql, etc...)
*
* @access public
* @return string
*/
function platform()
{
return $this->dbdriver;
}
// --------------------------------------------------------------------
/**
* Database Version Number. Returns a string containing the
* version of the database being used
*
* @access public
* @return string
*/
function version()
{
if (FALSE === ($sql = $this->_version()))
{
if ($this->db_debug)
{
return $this->display_error('db_unsupported_function');
}
return FALSE;
}
// Some DBs have functions that return the version, and don't run special
// SQL queries per se. In these instances, just return the result.
$driver_version_exceptions = array('oci8', 'sqlite', 'cubrid');
if (in_array($this->dbdriver, $driver_version_exceptions))
{
return $sql;
}
else
{
$query = $this->query($sql);
return $query->row('ver');
}
}
</pre>
<div class='alert alert-danger'>
那個_version函式的命名不好。未必會回傳版本數字，可能是一串查詢字。
</div>
<div class='alert alert-danger'>
錯誤處理機制與前面不一致。前面哪有把display_error的結果return？
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
/**
* Execute the query
*
* Accepts an SQL string as input and returns a result object upon
* successful execution of a "read" type query. Returns boolean TRUE
* upon successful execution of a "write" type query. Returns boolean
* FALSE upon failure, and if the $db_debug variable is set to TRUE
* will raise an error.
*
* @access public
* @param string An SQL query string
* @param array An array of binding data
* @return mixed
*/
function query($sql, $binds = FALSE, $return_object = TRUE)
{
if ($sql == '')
{
if ($this->db_debug)
{
log_message('error', 'Invalid query: '.$sql);
return $this->display_error('db_invalid_query');
}
return FALSE;
}
// Verify table prefix and replace if necessary
if ( ($this->dbprefix != '' AND $this->swap_pre != '') AND ($this->dbprefix != $this->swap_pre) )
{
$sql = preg_replace("/(\W)".$this->swap_pre."(\S+?)/", "\\1".$this->dbprefix."\\2", $sql);
}
// Compile binds if needed
if ($binds !== FALSE)
{
$sql = $this->compile_binds($sql, $binds);
}
// Is query caching enabled? If the query is a "read type"
// we will load the caching class and return the previously
// cached query if it exists
if ($this->cache_on == TRUE AND stristr($sql, 'SELECT'))
{
if ($this->_cache_init())
{
$this->load_rdriver();
if (FALSE !== ($cache = $this->CACHE->read($sql)))
{
return $cache;
}
}
}
// Save the query for debugging
if ($this->save_queries == TRUE)
{
$this->queries[] = $sql;
}
// Start the Query Timer
$time_start = list($sm, $ss) = explode(' ', microtime());
// Run the Query
if (FALSE === ($this->result_id = $this->simple_query($sql)))
{
if ($this->save_queries == TRUE)
{
$this->query_times[] = 0;
}
// This will trigger a rollback if transactions are being used
$this->_trans_status = FALSE;
if ($this->db_debug)
{
// grab the error number and message now, as we might run some
// additional queries before displaying the error
$error_no = $this->_error_number();
$error_msg = $this->_error_message();
// We call this function in order to roll-back queries
// if transactions are enabled. If we don't call this here
// the error message will trigger an exit, causing the
// transactions to remain in limbo.
$this->trans_complete();
// Log and display errors
log_message('error', 'Query error: '.$error_msg);
return $this->display_error(
array(
'Error Number: '.$error_no,
$error_msg,
$sql
)
);
}
return FALSE;
}
// Stop and aggregate the query time results
$time_end = list($em, $es) = explode(' ', microtime());
$this->benchmark += ($em + $es) - ($sm + $ss);
if ($this->save_queries == TRUE)
{
$this->query_times[] = ($em + $es) - ($sm + $ss);
}
// Increment the query counter
$this->query_count++;
// Was the query a "write" type?
// If so we'll simply return true
if ($this->is_write_type($sql) === TRUE)
{
// If caching is enabled we'll auto-cleanup any
// existing files related to this particular URI
if ($this->cache_on == TRUE AND $this->cache_autodel == TRUE AND $this->_cache_init())
{
$this->CACHE->delete();
}
return TRUE;
}
// Return TRUE if we don't need to create a result object
// Currently only the Oracle driver uses this when stored
// procedures are used
if ($return_object !== TRUE)
{
return TRUE;
}
// Load and instantiate the result driver
$driver = $this->load_rdriver();
$RES = new $driver();
$RES->conn_id = $this->conn_id;
$RES->result_id = $this->result_id;
if ($this->dbdriver == 'oci8')
{
$RES->stmt_id = $this->stmt_id;
$RES->curs_id = NULL;
$RES->limit_used = $this->limit_used;
$this->stmt_id = FALSE;
}
// oci8 vars must be set before calling this
$RES->num_rows = $RES->num_rows();
// Is query caching enabled? If so, we'll serialize the
// result object and save it to a cache file.
if ($this->cache_on == TRUE AND $this->_cache_init())
{
// We'll create a new instance of the result object
// only without the platform specific driver since
// we can't use it with cached data (the query result
// resource ID won't be any good once we've cached the
// result object, so we'll have to compile the data
// and save it)
$CR = new CI_DB_result();
$CR->num_rows = $RES->num_rows();
$CR->result_object = $RES->result_object();
$CR->result_array = $RES->result_array();
// Reset these since cached objects can not utilize resource IDs.
$CR->conn_id = NULL;
$CR->result_id = NULL;
$this->CACHE->write($sql, $CR);
}
return $RES;
}
// --------------------------------------------------------------------
/**
* Load the result drivers
*
* @access public
* @return string the name of the result class
*/
function load_rdriver()
{
$driver = 'CI_DB_'.$this->dbdriver.'_result';
if ( ! class_exists($driver))
{
include_once(BASEPATH.'database/DB_result.php');
include_once(BASEPATH.'database/drivers/'.$this->dbdriver.'/'.$this->dbdriver.'_result.php');
}
return $driver;
}
</pre>
<div class='alert alert-success'>
根據driver成員變數去載入db driver。<br/>
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
/**
* Simple Query
* This is a simplified version of the query() function. Internally
* we only use it when running transaction commands since they do
* not require all the features of the main query() function.
*
* @access public
* @param string the sql query
* @return mixed
*/
function simple_query($sql)
{
if ( ! $this->conn_id)
{
$this->initialize();
}
return $this->_execute($sql);
}
// --------------------------------------------------------------------
/**
* Disable Transactions
* This permits transactions to be disabled at run-time.
*
* @access public
* @return void
*/
function trans_off()
{
$this->trans_enabled = FALSE;
}
</pre>
<div class='alert alert-success'>
關閉transaction功能。
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
/**
* Enable/disable Transaction Strict Mode
* When strict mode is enabled, if you are running multiple groups of
* transactions, if one group fails all groups will be rolled back.
* If strict mode is disabled, each group is treated autonomously, meaning
* a failure of one group will not affect any others
*
* @access public
* @return void
*/
function trans_strict($mode = TRUE)
{
$this->trans_strict = is_bool($mode) ? $mode : TRUE;
}
// --------------------------------------------------------------------
/**
* Start Transaction
*
* @access public
* @return void
*/
function trans_start($test_mode = FALSE)
{
if ( ! $this->trans_enabled)
{
return FALSE;
}
// When transactions are nested we only begin/commit/rollback the outermost ones
if ($this->_trans_depth > 0)
{
$this->_trans_depth += 1;
return;
}
$this->trans_begin($test_mode);
}
// --------------------------------------------------------------------
/**
* Complete Transaction
*
* @access public
* @return bool
*/
function trans_complete()
{
if ( ! $this->trans_enabled)
{
return FALSE;
}
// When transactions are nested we only begin/commit/rollback the outermost ones
if ($this->_trans_depth > 1)
{
$this->_trans_depth -= 1;
return TRUE;
}
// The query() function will set this flag to FALSE in the event that a query failed
if ($this->_trans_status === FALSE)
{
$this->trans_rollback();
// If we are NOT running in strict mode, we will reset
// the _trans_status flag so that subsequent groups of transactions
// will be permitted.
if ($this->trans_strict === FALSE)
{
$this->_trans_status = TRUE;
}
log_message('debug', 'DB Transaction Failure');
return FALSE;
}
$this->trans_commit();
return TRUE;
}
// --------------------------------------------------------------------
/**
* Lets you retrieve the transaction flag to determine if it has failed
*
* @access public
* @return bool
*/
function trans_status()
{
return $this->_trans_status;
}
// --------------------------------------------------------------------
/**
* Compile Bindings
*
* @access public
* @param string the sql statement
* @param array an array of bind data
* @return string
*/
function compile_binds($sql, $binds)
{
if (strpos($sql, $this->bind_marker) === FALSE)
{
return $sql;
}
if ( ! is_array($binds))
{
$binds = array($binds);
}
// Get the sql segments around the bind markers
$segments = explode($this->bind_marker, $sql);
// The count of bind should be 1 less then the count of segments
// If there are more bind arguments trim it down
if (count($binds) >= count($segments)) {
$binds = array_slice($binds, 0, count($segments)-1);
}
// Construct the binded query
$result = $segments[0];
$i = 0;
foreach ($binds as $bind)
{
$result .= $this->escape($bind);
$result .= $segments[++$i];
}
return $result;
}
// --------------------------------------------------------------------
/**
* Determines if a query is a "write" type.
*
* @access public
* @param string An SQL query string
* @return boolean
*/
function is_write_type($sql)
{
if ( ! preg_match('/^\s*"?(SET|INSERT|UPDATE|DELETE|REPLACE|CREATE|DROP|TRUNCATE|LOAD DATA|COPY|ALTER|GRANT|REVOKE|LOCK|UNLOCK)\s+/i', $sql))
{
return FALSE;
}
return TRUE;
}
// --------------------------------------------------------------------
/**
* Calculate the aggregate query elapsed time
*
* @access public
* @param integer The number of decimal places
* @return integer
*/
function elapsed_time($decimals = 6)
{
return number_format($this->benchmark, $decimals);
}
// --------------------------------------------------------------------
/**
* Returns the total number of queries
*
* @access public
* @return integer
*/
function total_queries()
{
return $this->query_count;
}
// --------------------------------------------------------------------
/**
* Returns the last query that was executed
*
* @access public
* @return void
*/
function last_query()
{
return end($this->queries);
}
// --------------------------------------------------------------------
/**
* "Smart" Escape String
*
* Escapes data based on type
* Sets boolean and null types
*
* @access public
* @param string
* @return mixed
*/
function escape($str)
{
if (is_string($str))
{
$str = "'".$this->escape_str($str)."'";
}
elseif (is_bool($str))
{
$str = ($str === FALSE) ? 0 : 1;
}
elseif (is_null($str))
{
$str = 'NULL';
}
return $str;
}
// --------------------------------------------------------------------
/**
* Escape LIKE String
*
* Calls the individual driver for platform
* specific escaping for LIKE conditions
*
* @access public
* @param string
* @return mixed
*/
function escape_like_str($str)
{
return $this->escape_str($str, TRUE);
}
// --------------------------------------------------------------------
/**
* Primary
*
* Retrieves the primary key. It assumes that the row in the first
* position is the primary key
*
* @access public
* @param string the table name
* @return string
*/
function primary($table = '')
{
$fields = $this->list_fields($table);
if ( ! is_array($fields))
{
return FALSE;
}
return current($fields);
}
// --------------------------------------------------------------------
/**
* Returns an array of table names
*
* @access public
* @return array
*/
function list_tables($constrain_by_prefix = FALSE)
{
// Is there a cached result?
if (isset($this->data_cache['table_names']))
{
return $this->data_cache['table_names'];
}
if (FALSE === ($sql = $this->_list_tables($constrain_by_prefix)))
{
if ($this->db_debug)
{
return $this->display_error('db_unsupported_function');
}
return FALSE;
}
$retval = array();
$query = $this->query($sql);
if ($query->num_rows() > 0)
{
foreach ($query->result_array() as $row)
{
if (isset($row['TABLE_NAME']))
{
$retval[] = $row['TABLE_NAME'];
}
else
{
$retval[] = array_shift($row);
}
}
}
$this->data_cache['table_names'] = $retval;
return $this->data_cache['table_names'];
}
// --------------------------------------------------------------------
/**
* Determine if a particular table exists
* @access public
* @return boolean
*/
function table_exists($table_name)
{
return ( ! in_array($this->_protect_identifiers($table_name, TRUE, FALSE, FALSE), $this->list_tables())) ? FALSE : TRUE;
}
// --------------------------------------------------------------------
/**
* Fetch MySQL Field Names
*
* @access public
* @param string the table name
* @return array
*/
function list_fields($table = '')
{
// Is there a cached result?
if (isset($this->data_cache['field_names'][$table]))
{
return $this->data_cache['field_names'][$table];
}
if ($table == '')
{
if ($this->db_debug)
{
return $this->display_error('db_field_param_missing');
}
return FALSE;
}
if (FALSE === ($sql = $this->_list_columns($table)))
{
if ($this->db_debug)
{
return $this->display_error('db_unsupported_function');
}
return FALSE;
}
$query = $this->query($sql);
$retval = array();
foreach ($query->result_array() as $row)
{
if (isset($row['COLUMN_NAME']))
{
$retval[] = $row['COLUMN_NAME'];
}
else
{
$retval[] = current($row);
}
}
$this->data_cache['field_names'][$table] = $retval;
return $this->data_cache['field_names'][$table];
}
// --------------------------------------------------------------------
/**
* Determine if a particular field exists
* @access public
* @param string
* @param string
* @return boolean
*/
function field_exists($field_name, $table_name)
{
return ( ! in_array($field_name, $this->list_fields($table_name))) ? FALSE : TRUE;
}
// --------------------------------------------------------------------
/**
* Returns an object with field data
*
* @access public
* @param string the table name
* @return object
*/
function field_data($table = '')
{
if ($table == '')
{
if ($this->db_debug)
{
return $this->display_error('db_field_param_missing');
}
return FALSE;
}
$query = $this->query($this->_field_data($this->_protect_identifiers($table, TRUE, NULL, FALSE)));
return $query->field_data();