PHP与MySQL索引的并发读写和并发更新的性能优化策略及其对性能的影响

// 配置主从数据库信息
$masterDB = new MySQLi('master_host', 'master_user', 'master_password');
$slaveDB = new MySQLi('slave_host', 'slave_user', 'slave_password');

// 读操作连接从库
function querySlave($sql) {
  global $slaveDB;
  return $slaveDB->query($sql);
}

// 写操作连接主库
function queryMaster($sql) {
  global $masterDB;
  return $masterDB->query($sql);
}

// 初始化数据库连接池
$connectionPool = new ConnectionPool();

// 从连接池获取数据库连接
$connection = $connectionPool->getConnection();

// 执行SQL操作
$result = $connection->query("SELECT * FROM table");

// 将连接释放回连接池
$connectionPool->releaseConnection($connection);

// 组织批量更新的SQL语句
$sql = "UPDATE table SET field1 = value1 WHERE condition1;
        UPDATE table SET field2 = value2 WHERE condition2;
        UPDATE table SET field3 = value3 WHERE condition3;"

// 执行批量更新
$mysqli->multi_query($sql);

// 使用乐观锁
// 假设表结构中存在version字段，每次更新时进行版本号校验
$version = $mysqli->query("SELECT version FROM table WHERE id = 1")->fetch_assoc()["version"];
$result = $mysqli->query("UPDATE table SET field = value, version = version+1 WHERE id = 1 AND version = $version");

// 使用悲观锁
$mysqli->query("START TRANSACTION");
$mysqli->query("SELECT * FROM table WHERE id = 1 FOR UPDATE");
$mysqli->query("UPDATE table SET field = value WHERE id = 1");
$mysqli->query("COMMIT");