Php導出百萬數據的優化

導出數據量很大的情況下，生成excel的內存需求非常龐大，服務器吃不消，這個時候考慮生成csv來解決問題，cvs讀寫性能比excel高。
測試表student 數據(大家可以腳本插入300多萬測數據。這里只給個簡單的示例了)

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student`  (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  `StuNo` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `StuName` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `StuAge` int(11) NULL DEFAULT NULL,
  PRIMARY KEY (`ID`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 12 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES (1, 'A001', '小明', 22);
INSERT INTO `student` VALUES (2, 'A005', '小李', 23);
INSERT INTO `student` VALUES (3, 'A007', '小紅', 24);
INSERT INTO `student` VALUES (4, 'A003', '小明', 22);
INSERT INTO `student` VALUES (5, 'A002', '小李', 23);
INSERT INTO `student` VALUES (6, 'A004', '小紅', 24);
INSERT INTO `student` VALUES (7, 'A006', '小王', 25);
INSERT INTO `student` VALUES (8, 'A008', '喬峰', 27);
INSERT INTO `student` VALUES (9, 'A009', '歐陽克', 22);
INSERT INTO `student` VALUES (10, 'A010', '老頑童', 34);
INSERT INTO `student` VALUES (11, 'A011', '黃老邪', 33);

SET FOREIGN_KEY_CHECKS = 1;

導出腳本export.php

<?php
set_time_limit(0);
ini_set('memory_limit', '128M');

$fileName = date('YmdHis', time());
header('Content-Encoding: UTF-8');
header("Content-type:application/vnd.ms-excel;charset=UTF-8");
header('Content-Disposition: attachment;filename="' . $fileName . '.csv"');
//注意，數據量在大的情況下。比如導出幾十萬到幾百萬，會出現504 Gateway Time-out,請修改php.ini的max_execution_time參數
//打開php標准輸出流以寫入追加的方式打開
$fp = fopen('php://output', 'a');
//連接數據庫
$dbhost = '127.0.0.1';
$dbuser = 'root';
$dbpwd = 'root';
$con = mysqli_connect($dbhost, $dbuser, $dbpwd);
if (mysqli_connect_errno())
    die('connect error');

$database = 'test';//選擇數據庫
mysqli_select_db($con, $database);
mysqli_query($con, "set names UTF8");//如果需要請設置編碼

//用fputcsv從數據庫中導出1百萬的數據,比如我們每次取1萬條數據，分100步來執行
//一次性讀取1萬條數據，也可以把$nums調小，$step相應增大。
$step = 100;
$nums = 10000;
$where = "where 1=1"; //篩選條件,可自行添加

//設置標題
$title = array('id', '編號', '姓名', '年齡'); //注意這里是小寫id,否則ID命名打開會提示Excel 已經檢測到"xxx.xsl"是SYLK文件,但是不能將其加載: CSV 文或者XLS文件的前兩個字符是大寫字母"I"，"D"時，會發生此問題。
foreach ($title as $key => $item)
    $title[$key] = iconv("UTF-8", "GB2312//IGNORE", $item);

fputcsv($fp, $title);

for ($s = 1; $s <= $step; $s++) {
    $start = ($s - 1) * $nums;
    $result = mysqli_query($con, "SELECT ID,StuNo,StuName,StuAge FROM `student` " . $where . " ORDER BY `ID` LIMIT {$start},{$nums}");
    if ($result) {
        while ($row = mysqli_fetch_assoc($result)) {
            foreach ($row as $key => $item)
                $row[$key] = iconv("UTF-8", "GBK", $item); //這里必須轉碼，不然會亂碼
            fputcsv($fp, $row);
        }
        mysqli_free_result($result); //釋放結果集資源
        ob_flush();  //每1萬條數據就刷新緩沖區
        flush();
    }
}
mysqli_close($con);//斷開連接

導出效果：