search
HomeDatabaseMysql TutorialBuffered and Unbuffered queries and non-cached query examples of pdo in MySQL

MySQL's Buffered and Unbuffered queries

Today we will further talk about the advanced functions of MySQL's query cache, that is, query cache and query uncaching!

Cause: (memory overflow warning)

PHP Fatal error: Allowed memory size of 268 435 456 bytes exhausted

1. Official

Buffered and Unbuffered queries and non-cached query examples of pdo in MySQLMainly say that the cache query is as follows If you check out all the content and put it into the memory, it will accumulate more and more; while the non-cached query will directly return one by one from the MySQL server, which means it will wait for the PHP process to get the next piece of data. (It’s enough to mainly understand this meaning. If you want to fully understand, please translate on Weibo or Baidu)

2.Buffer and unBuffer query

a ) Cache queries are generally used to obtain query data at one time and will be stored in memory;

b) Non-cache queries are returned directly from MySQL one by one and will not be stored in memory;

3.mysqli, non-cache query example of pdo

<?php##mysqli
    $mysqli  = new mysqli("localhost", "my_user", "my_password", "world");
    $uresult = $mysqli->query("SELECT Name FROM City", MYSQLI_USE_RESULT);
    if ($uresult) {   
        while ($row = $uresult->fetch_assoc()) {       
            echo $row[&#39;Name&#39;] . PHP_EOL;
       }
    }
    $uresult->close();
    
##pdo
    $pdo = new PDO("mysql:host=localhost;dbname=world", &#39;my_user&#39;, &#39;my_pass&#39;);
    $pdo->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, false);
    $uresult = $pdo->query("SELECT Name FROM City");
    if ($uresult) {   
           while ($row = $uresult->fetch(PDO::FETCH_ASSOC)) {       
               echo $row[&#39;Name&#39;] . PHP_EOL;
          }
    }
##mysql 会被抛弃的,了解下即可
    $conn = mysql_connect("localhost", "my_user", "my_pass");
    $db   = mysql_select_db("world");
    $uresult = mysql_unbuffered_query("SELECT Name FROM City");
    if ($uresult) {   
           while ($row = mysql_fetch_assoc($uresult)) {       
                   echo $row[&#39;Name&#39;] . PHP_EOL;
           }
    }

Summary:
Here Cached queries and non-cached queries actually cause memory overflow when operating a large amount of data. At this time, non-cached queries can be used to prevent this situation from happening, but you have to pay attention at this time. Because mysql will wait for the PHP program to obtain the data until all the data is obtained, it will consume the performance of MySQL. So how do we use them correctly? We have to specifically grasp the core, memory overflow, and MySQL performance consumption. This If you grasp 2 well, you will know what scene to use it in. If you still don’t know how to use it, you can leave a message or tweet me!

Related articles:

How MySQL 'queries' and 'questions' are measured

How to find and kill misbehaving MySQL queries

Related videos:

Han Shunping’s latest MySQL basic video tutorial in 2016

The above is the detailed content of Buffered and Unbuffered queries and non-cached query examples of pdo in MySQL. For more information, please follow other related articles on the PHP Chinese website!

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
图文详解mysql架构原理图文详解mysql架构原理May 17, 2022 pm 05:54 PM

本篇文章给大家带来了关于mysql的相关知识,其中主要介绍了关于架构原理的相关内容,MySQL Server架构自顶向下大致可以分网络连接层、服务层、存储引擎层和系统文件层,下面一起来看一下,希望对大家有帮助。

mysql怎么替换换行符mysql怎么替换换行符Apr 18, 2022 pm 03:14 PM

在mysql中,可以利用char()和REPLACE()函数来替换换行符;REPLACE()函数可以用新字符串替换列中的换行符,而换行符可使用“char(13)”来表示,语法为“replace(字段名,char(13),'新字符串') ”。

mysql怎么去掉第一个字符mysql怎么去掉第一个字符May 19, 2022 am 10:21 AM

方法:1、利用right函数,语法为“update 表名 set 指定字段 = right(指定字段, length(指定字段)-1)...”;2、利用substring函数,语法为“select substring(指定字段,2)..”。

mysql的msi与zip版本有什么区别mysql的msi与zip版本有什么区别May 16, 2022 pm 04:33 PM

mysql的msi与zip版本的区别:1、zip包含的安装程序是一种主动安装,而msi包含的是被installer所用的安装文件以提交请求的方式安装;2、zip是一种数据压缩和文档存储的文件格式,msi是微软格式的安装包。

mysql怎么将varchar转换为int类型mysql怎么将varchar转换为int类型May 12, 2022 pm 04:51 PM

转换方法:1、利用cast函数,语法“select * from 表名 order by cast(字段名 as SIGNED)”;2、利用“select * from 表名 order by CONVERT(字段名,SIGNED)”语句。

MySQL复制技术之异步复制和半同步复制MySQL复制技术之异步复制和半同步复制Apr 25, 2022 pm 07:21 PM

本篇文章给大家带来了关于mysql的相关知识,其中主要介绍了关于MySQL复制技术的相关问题,包括了异步复制、半同步复制等等内容,下面一起来看一下,希望对大家有帮助。

带你把MySQL索引吃透了带你把MySQL索引吃透了Apr 22, 2022 am 11:48 AM

本篇文章给大家带来了关于mysql的相关知识,其中主要介绍了mysql高级篇的一些问题,包括了索引是什么、索引底层实现等等问题,下面一起来看一下,希望对大家有帮助。

mysql怎么判断是否是数字类型mysql怎么判断是否是数字类型May 16, 2022 am 10:09 AM

在mysql中,可以利用REGEXP运算符判断数据是否是数字类型,语法为“String REGEXP '[^0-9.]'”;该运算符是正则表达式的缩写,若数据字符中含有数字时,返回的结果是true,反之返回的结果是false。

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Safe Exam Browser

Safe Exam Browser

Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

SublimeText3 Linux new version

SublimeText3 Linux new version

SublimeText3 Linux latest version

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)