This article will introduce you to the DBA extension of PHP in detail. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

Extended DBA learning in PHP

The DBA we are talking about today is not the traditional database administrator DBA, but a Buckley style in PHP Database extensions. The Buckley style database is actually what we often call a K/V database in the form of key-value pairs. Just like memcached or redis, which we usually use a lot, only one key corresponds to one value, but memcached mainly stores them in memory, while DBA extension stores data in files, just like a simple key Same as SQLite in value pair form.

The database types used by DBA extensions are basically open source, and deployment and release are very simple. It is just a db file, so it is very similar to SQLite. But the disadvantage is that it will load the database file into the memory at once. We cannot make the database too large, otherwise it will burst the memory. The DBA database is always together with the program, so it does not have network-related interfaces. We generally only use this kind of database locally in the code.

When installing, we need to add the --enable-dba=shared configuration during compilation, and then add an --enable-XXXX configuration. XXXX refers to the Buckley style database we want to use. Types, the more common ones include dbm, ndbm, gdbm, db2, etc. Similarly, the operating system also needs to install these related software. For example, our system is installed with gdbm, which needs to be installed using yum install.

A simple example

First let’s look at the code to see how our DBA database is used.

// 打开一个数据库文件
$id = dba_open("/tmp/test.db", "n", "gdbm");
//$id = dba_popen("/tmp/test1.db", "c", "gdbm");

// 添加或替换一个内容
dba_replace("key1", "This is an example!", $id);

// 如果内容存在
if(dba_exists("key1", $id)){
    // 读取内容
    echo dba_fetch("key1", $id), PHP_EOL;
    // This is an example!
}

dba_close($id);

First, use dba_open() to open a database file, the first parameter is the path of the database file, the second parameter is the opening method, including r, w, c, n, r means read-only, w means read-write, c means create plus read-write, n means if not It is created and can be read and written. The third parameter is the specified database type. Only the gdbm library is installed in our system, so we use gdbm as the parameter. Like mysql, we can also use dba_popen() to open a persistent link to a data file.

dba_replace() function is to add or replace a piece of data. If the data does not exist, add a new one. If the data exists, replace the value of the corresponding key. The first parameter is key, and the second parameter is the value of the data.

dba_exists() is to determine whether the specified key exists. If it exists, we will obtain the data specified by the key through dba_fetch() in this if.

dba_close() is just like other data operation handles, it closes the database connection handle.

Add, traverse, and delete data

In the above example, we use dba_replace() to add data. In fact, there are special functions for regular data addition.

// 添加数据
dba_insert("key2","This is key2!", $id);
dba_insert("key3","This is key3!", $id);
dba_insert("key4","This is key4!", $id);
dba_insert("key5","This is key5!", $id);
dba_insert("key6","This is key6!", $id);

// 获取第一个 key
$key = dba_firstkey($id);

$handle_later = [];
while ($key !== false) {
    if (true) {
        // 将 key 保存到数组中
        $handle_later[] = $key;
    }
    // 获取下一个 key
    $key = dba_nextkey($id);
}

// 遍历 key 数组，打印数据库中的全部内容
foreach ($handle_later as $val) {
    echo dba_fetch($val, $id), PHP_EOL;
    dba_delete($val, $id); // 删除key对应的内容
}
// This is key4!
// This is key2!
// This is key3!
// This is an example!
// This is key5!
// This is key6!

dba_insert() is to insert data. It will not replace the existing key data. If it is to insert the existing key information, it will return false.

dba_firstkey() is used to get the first key, dba_nextkey() is used to get the next key. Through these two functions, we can get all the key information in the entire database, and then we can These keys are used to traverse everything in the entire database.

dba_delete() deletes a piece of data based on the key.

Optimization and synchronization database

Even if it is mysql, after long-term use, we also need to do some sorting and optimization work, such as letting mysql automatically defragment files, organize indexes, etc., it uses The SQL statement is: optimize table name. In the same way, DBA extension also provides us with such a function.

// 优化数据库
var_dump(dba_optimize($id)); // bool(true)

In addition, just like the cache of mysql, the DBA will also cache when operating data. At this time, we can use a function to force the data in the cache to be flushed into the hard disk file.

// 同步数据库
var_dump(dba_sync($id)); // bool(true)

Currently open database list

We can use a function to see which data connections are currently open, because DBA is a simple file-based database, so we can open it in a piece of code Multiple data connections.

// 获取当前打开的数据库列表
var_dump(dba_list());
// array(1) {
//     [4]=>
//     string(12) "/tmp/test.db"
//   }

Database types supported by the system

Finally, let’s look at a supported function, which can return the database types currently supported by our database.

// 当前支持的数据库类型
var_dump(dba_handlers(true));
// array(5) {
//     ["gdbm"]=>
//     string(58) "GDBM version 1.18. 21/08/2018 (built May 11 2019 01:10:11)"
//     ["cdb"]=>
//     string(53) "0.75, $Id: 841505a20a8c9c8e35cac5b5dc3d5cf2fe917478 $"
//     ["cdb_make"]=>
//     string(53) "0.75, $Id: 95b1c2518144e0151afa6b2b8c7bf31bf1f037ed $"
//     ["inifile"]=>
//     string(52) "1.0, $Id: 42cb3bb7617b5744add2ab117b45b3a1e37e7175 $"
//     ["flatfile"]=>
//     string(52) "1.0, $Id: 410f3405266f41bafffc8993929b8830b761436b $"
//   }

var_dump(dba_handlers(false));
// array(5) {
//     [0]=>
//     string(4) "gdbm"
//     [1]=>
//     string(3) "cdb"
//     [2]=>
//     string(8) "cdb_make"
//     [3]=>
//     string(7) "inifile"
//     [4]=>
//     string(8) "flatfile"
//   }

dba_handlers() has a Boolean parameter. From the code, we can see that the function of this parameter is the detailed level of the returned information.

Summary

What we introduced today is a very simple set of database extension components. Its functions are just these. In daily production environments, there are not many actual application scenarios. We can use PHP file serialization to save simple key-value pairs, while caching will mostly use tools such as memcached, so you can learn about it.

Test code:

https://github.com/zhangyue0503/dev-blog/blob/master/php/202008/PHP%E7%9A%84DBA%E6%89%A9%E5%B1%95%E5%AD%A6%E4%B9%A0.md

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