php导致内存溢出
在执行一个导出csv脚步时,当要导出的数据超过3w多条时,就会报错,如下:
Allowed memory size of 134217728 bytes exhausted (tried to allocate 20480 bytes)
php存储3w多条数据这个数组占用内存超过20M
解决方法:分批取数据,分批处理数据
问题点:一次取多少数据最合适
一次取1w条,减少数据库IO操作次数,但php数组就好较大
一次取1k条,增加了数据库IO操作次数,php数组很小
数据一共41000条
因为是循环查询数据,只能返回空,所以会有一次无效的IO查询
每次请求次数 | 响应时间 | 数组库IO次数 |
---|---|---|
5000 | 11.34 | 10 |
1000 | 8.02 | 6 |
2000 | 7.07 | 4 |
3000 | 5.12 | 3 |
4000 | 4.93 | 3 |
综合考虑,觉得使用每次请求1w条数据
代码简单记录下
$filename = '测试';
$head = array('申请时间', '省', '市', '超市品牌');
$field = array('created_time', 'pro_name', 'city_name', 'brand_name');
$csv = ExportCsvService::getInstance(implode(",", $head), $field, $filename);
$param['limit'] = C('SQL_LIMIT');
$i = 0;
while (true) {
$param['current'] = $i + 1;
$info = $rainbowservice->get_list($param)['data']['list'];
if (empty($info)) {
$csv->end();
break;
} else {
$csv->sendDate($info);
}
unset($info);
$i++;
}
csv操作类
class ExportCsvService
{
private $content;
private $filename;
private $field;
private static $instance;
private function __construct($head,$field,$filename)
{
$this->field = $field;
$this->filename = $filename;
$this->content = iconv('UTF-8', 'GBK',$head) . PHP_EOL;
}
/**
* 实例化服务类
* @param $head
* @param $field
* @param $filename
* @return ExportCsvService
*/
public static function getInstance($head,$field,$filename) {
if (!self::$instance instanceof self) {
self::$instance = new self($head,$field,$filename);
}
return self::$instance;
}
/**
* 拼接要导出的数据
* @param $data
*/
public function sendDate($data) {
foreach ($data as $key => $value) {
$temp = [];
foreach ($this->field as $k) {
$temp[] = iconv('UTF-8', 'GBK', $value[$k]);
}
$this->content .= implode(",", $temp) . PHP_EOL; //用英文逗号分开
unset($temp);
}
}
/**
* 输出数据
*/
public function end() {
header("Content-type:text/csv;charset=GBK");
header("Content-Disposition:attachment;filename=" . $this->filename);
header('Cache-Control:must-revalidate,post-check=0,pre-check=0');
header('Expires:0');
header('Pragma:public');
echo $this->content;
}
}