Php 在Codeigniter中使用$db['；读写'；]和$db['；读写创建'；]的目的是什么？

在Codeigniter中的

database.php

（

application/config/database.php

）中使用

$db['read-write']]

和

$db['read-write-create']

的目的是什么？请帮我找到答案

$db['read-write'] = array(
    'dsn' => '',
    'hostname' => 'localhost',
    'username' => 'root',
    'password' => 'root',
    'database' => 'db_test',
    'dbdriver' => 'mysqli',
    'dbprefix' => '',
    'pconnect' => FALSE,
    'db_debug' => (ENVIRONMENT !== 'production') ,
    'cache_on' => FALSE,
    'cachedir' => '',
    'char_set' => 'utf8',
    'dbcollat' => 'utf8_general_ci',
    'swap_pre' => '',
    'encrypt' => FALSE,
    'compress' => FALSE,
    'stricton' => FALSE,
    'failover' => array() ,
    'save_queries' => TRUE
);
$db['read-write-create'] = array(
    'dsn' => '',
    'hostname' => 'localhost',
    'username' => 'root',
    'password' => 'root',
    'database' => 'db_test',
    'dbdriver' => 'mysqli',
    'dbprefix' => '',
    'pconnect' => FALSE,
    'db_debug' => (ENVIRONMENT !== 'production') ,
    'cache_on' => FALSE,
    'cachedir' => '',
    'char_set' => 'utf8',
    'dbcollat' => 'utf8_general_ci',
    'swap_pre' => '',
    'encrypt' => FALSE,
    'compress' => FALSE,
    'stricton' => FALSE,
    'failover' => array() ,
    'save_queries' => TRUE
);

---

阅读此内容：只读副本通常用于性能原因或故障转移情况。名称“读写”和“读写创建”是任意的。它可以是你想要的任何东西。默认情况下，codeigniter对主连接使用“default”一词，但也可以将其重命名为与项目更相关的名称。