表250万行，可能是磁盘空间不够(存放数据的盘只有5G空闲空间)的情况下出现失败：

ALTER TABLE pre_answers_caiji9 ENGINE=InnoDB
1114 - The table '#sql-6b33_1d98828' is full

分步操作，新建表再复制数据的方式进行：

CREATE TABLE pre_answers_caiji9_new LIKE pre_answers_caiji9;
ALTER TABLE pre_answers_caiji9_new ENGINE=InnoDB;

INSERT INTO pre_answers_caiji9_new SELECT * FROM pre_answers_caiji9 WHERE id BETWEEN 1 AND 1000000;
INSERT INTO pre_answers_caiji9_new SELECT * FROM pre_answers_caiji9 WHERE id BETWEEN 1000001 AND 2000000;
-- 继续插入剩余的数据, 一次1百万行太久，可降低到10万...

-- 重命名表
RENAME TABLE pre_answers_caiji9 TO pre_answers_caiji9_old, pre_answers_caiji9_new TO pre_answers_caiji9;

--删除旧表
DROP TABLE pre_answers_caiji9_old;

        //复制图片功能
        $(document).on('click', ".j-copy-image", function(e) {
            var img = $('#' + $(this).data('target'))[0]
            var canvas = document.createElement('canvas')
            canvas.width = img.naturalWidth
            canvas.height = img.naturalHeight
            var ctx = canvas.getContext('2d');
            ctx.drawImage(img, 0, 0)
            canvas.toBlob(async blob => {
                const data = [
                    new ClipboardItem({
                        [blob.type]: blob,
                    }),
                ];
                await navigator.clipboard.write(data)
                    .then(
                        () => {
                            simpleDialog({
                                msg: '复制成功'
                            })
                        },
                        () => {
                            simpleDialog({
                                msg: '复制失败，请右键选择【复制图像】'
                            })
                        }
                    );
            });
        })

ls -l 显示年份
默认情况下ls -l命令只显示月和日，不显示年份：

$ ls -l
lrwxrwxrwx 1 root root 7 Feb 27 16:12 bin -> usr/bin

如要要显示年份，就要使用--time-style参数，该参数有几个选项

• full-iso 精确显示年月日时分秒纳秒及时区
• long-iso 显示年月日时分
• iso 默认就是iso，显示月日时分
• locale 按当前系统环境区域设置显示

+Format 自定义格式显示

所以要显示年份可以使用full-iso、long-iso、+Format这几种参数选项。

$ ls -l --time-style=full-iso
lrwxrwxrwx 1 root root 7 2016-02-27 16:12:03.185940151 +0800 bin -> usr/bin
$ ls -l --time-style=long-iso
lrwxrwxrwx 1 root root 7 2016-02-27 16:12 bin -> usr/bin
$ s -l --time-style="+%Y-%m-%d %H:%I:%S" 
lrwxrwxrwx 1 root root 7 2016-02-27 16:04:03 bin -> usr/bin

--time-style=full-iso有一个替代参数--full-time，可以直接用这个参数来显示精确的时间：

$ ls --full-time
lrwxrwxrwx 1 root root 7 2016-02-27 16:12:03.185940151 +0800 bin -> usr/bin

        $modelVF = new Visitors;
        $builder = $modelVF->getCommandBuilder();
        $command = $builder->createFindCommand($modelVF->tableName(), $criteria);
        $posts = $command->query();

/www/server/nginx/conf

proxy_temp_path /www/server/nginx/proxy_temp_dir;
proxy_cache_path /www/server/nginx/proxy_cache_dir levels=1:2 keys_zone=cache_one:20m inactive=1d max_size=5g;
client_body_buffer_size 512k;
proxy_connect_timeout 60;
proxy_read_timeout 60;
proxy_send_timeout 60;
proxy_buffer_size 32k;
proxy_buffers 4 64k;
proxy_busy_buffers_size 128k;
proxy_temp_file_write_size 128k;
proxy_next_upstream error timeout invalid_header http_500 http_503 http_404;
proxy_cache cache_one;