<?php
class CachedDB extends Database {
var $is_cached = null;
var $cache_id = '';
function CachedDB($config = 'default'){
parent::Database($config);
global $cfg_resource;
$this->_connection['cache_ttl'] = $cfg_resource[$config]['cache_ttl']? intval($cfg_resource[$config]['cache_ttl']) : 0;
$this->_connection['cache_path'] = $cfg_resource[$config]['cache_path']? $cfg_resource[$config]['cache_path'] : '';
$this->_connection['cache_prefix'] = $cfg_resource[$config]['cache_prefix']? $cfg_resource[$config]['cache_prefix'] : 'db_';
}
/**
* Check is the Database object is cached and not expired
*
* @param string $sql sql query
* @return boolean true|false
*/
function is_cached ($sql){
$this->cache_id = $this->_connection['cache_path'] . $this->_connection['cache_prefix'] . md5($sql);
//is it cached?
if($this->cached) return true;
//is it not cached?
if($this->_connection['cache_ttl'] <= 0 or !file_exists($this->cache_id)) return false;
//is it expired?
if(!($mtime = filemtime($this->cache_id))) return false;
if(($mtime + $this->_connection['cache_ttl']) < time()) {
//erase the cached template
@unlink($this->cache_id);
return false;
} else {
//cache the result of is_cached() call
$this->cached = true;
return true;
}
}
/**
* Reimplement the query method with caching system
*
* @param string $sql sql query
* @return integer number of affected rows
*/
function query($sql, $ttl=''){
if($ttl>0)
$this->_connection['cache_ttl'] = $ttl;
$return = 0;
if($this->is_cached($sql)){
//try to load object from disk
$vars = unserialize(file_get_contents($this->cache_id));
foreach($vars as $key=>$val)
eval("$"."this->$key = $"."vars['"."$key'];");
$return = $this->affected_rows;
}else{
//execute the query
$return = parent::query($sql);
//try to save it to disk
if($f = @fopen($this->cache_id,"w")){
$arr_tmp = array(
'results' => $this->results,
'metadata' => $this->metadata,
'insert_id' => $this->insert_id,
'affected_rows' => $this->affected_rows,
);
@fwrite($f,serialize($arr_tmp));
@fclose($f);
}else{
$this->error('Could not save db cache file');
}
}
return $return;
}
}
?>
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