Database sub-table optimization practice: application in PHP programming

In the face of concurrent access to massive data, the traditional single database architecture often leads to performance problems. Therefore, database sub-database and sub-table have become one of the necessary means to optimize database performance. This article will introduce in detail the practical methods and precautions for database sharding and table sharding in PHP programming.

1. What is database sharding?

Database sharding, referred to as sharding, refers to splitting a large database into multiple small databases, or Split a large table into multiple small tables and distribute them to different physical machines for storage and processing to improve the processing power and performance of the database. The advantages of sharding databases and sharding tables mainly include:

1. Improve the concurrent access capability of the database and alleviate the single point of failure problem.

2. Disperse data storage to improve the overall processing capability of the system.

3. Shorten data backup and recovery time and improve operation and maintenance efficiency.

4. Support horizontal expansion of business and reduce horizontal expansion costs.

2. Practice of sub-library and sub-table in PHP programming

1. Sub-library

In PHP programming, we can use one master and multiple slaves to achieve Branch library. In a one-master, multiple-slave architecture, write operations can only be performed in the master library, while read operations can be performed in multiple slave libraries. The specific implementation method is as follows:

1) First, you need to define a DB class to connect to the main library through PDO:

class DB{

private static $instance;
private $pdo;

private function __construct()
{
    $config = ['host' => '127.0.0.1',
               'port' => '3306',
               'dbname' => 'main',
               'username' => 'root',
               'password' => '123456',
               'driver' => 'mysql'
              ];
    $dsn = $config['driver'].":host=".$config['host'].";port=".$config['port'].";dbname=".$config['dbname'];
    $this->pdo = new PDO($dsn, $config['username'], $config['password']); 
}
public static function getInstance(){
    if(self::$instance === null){
        self::$instance = new self();
    }
    return self::$instance;
}
public function getPdo(){
    return $this->pdo;
}

}

2) Then, define a select method in the DB class, and randomly select a slave database for query:

public function select($sql, $params){

    try{
        $slave = ['slave1', 'slave2', 'slave3'];
        $dbIndex = array_rand($slave);
        $config = ['host' => '127.0.0.1',
                   'port' => '3306',
                   'dbname' => $slave[$dbIndex],
                   'username' => 'root',
                   'password' => '123456',
                   'driver' => 'mysql'
                  ];
        $dsn = $config['driver'].":host=".$config['host'].";port=".$config['port'].";dbname=".$config['dbname'];
        $pdo = new PDO($dsn, $config['username'], $config['password']);
        $stmt = $pdo->prepare($sql);
        $stmt->execute($params);
        $result = $stmt->fetchAll(PDO::FETCH_ASSOC);
        return $result;
    }catch(PDOException $e){
        die($e->getMessage());     
    }   

}

Through the above method, we can randomly select a slave database for query during the read operation, thereby achieving database partitioning.

2. Table splitting

In PHP programming, we can use the parity of ID to disperse data into different tables. If the ID is an even number, it is stored in the even table, if the ID is odd, it is stored in the odd table. The specific implementation method is as follows:

1) First, define a DbUtil class to connect the database and table partitioning logic:

class DbUtil{

private static $instance;
private $pdo;

private function __construct(){
    $config = ['host' => '127.0.0.1',
               'port' => '3306',
               'dbname' => 'test',
               'username' => 'root',
               'password' => '123456',
               'driver' => 'mysql'
              ];
    $dsn = $config['driver'].":host=".$config['host'].";port=".$config['port'].";dbname=".$config['dbname'];
    $this->pdo = new PDO($dsn, $config['username'], $config['password']); 
    $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}

public static function getInstance(){
    if(self::$instance === null){
        self::$instance = new self();
    }
    return self::$instance;
}

public function getPdo(){
    return $this->pdo;
}

public function selectById($id){
    $tableName = self::getTableName($id);
    $sql = "SELECT * FROM ".$tableName." WHERE id=:id";
    $params = [':id' => $id];
    $stmt = $this->pdo->prepare($sql);
    $stmt->execute($params);
    $result = $stmt->fetchAll(PDO::FETCH_ASSOC);
    return $result;
}

private static function getTableName($id){
    $isEven = $id % 2 == 0;
    if($isEven){
        return 'even_table';
    }else{
        return 'odd_table';
    }
}

}

2) Then, implement in the client code:

$id = 123;
$dbUtil = DbUtil::getInstance();
$result = $dbUtil->selectById($id );

Through the above method, we can disperse the data into different tables according to the parity of the ID.

3. Precautions for database sharding and table sharding

1. Data consistency issues: After sharding databases and tables, since the data is scattered in multiple libraries/tables, it may cause Data inconsistency problem. When sharding databases and tables, you need to consider consistency issues and use technologies such as consistent hashing or master-slave synchronization to achieve data synchronization.
2. Scenario selection of sub-database and sub-table: Only when the amount of data is very large, you need to use sub-database and sub-table. For businesses with a small amount of data, a stand-alone database can be used to process it.
3. Optimization of SQL statements: After sharding databases and tables, SQL statements need to be optimized to improve query efficiency. Optimization methods include: using indexes appropriately, avoiding the use of subqueries, merging simplified query statements, etc.

4. Summary

In PHP programming, in order to improve the processing power and performance of the database, we can use the method of sub-database and sub-table. Sub-database and sub-table can improve the concurrent processing capability of the system while reducing the risk of single points of failure. However, before using sub-databases and sub-tables, you need to consider data consistency issues and optimize SQL statements to improve database query efficiency.

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