Yii2：支持MySQL和PostgreSQL

Question

我的Yii2应用程序应该允许客户使用MySQL或PostgreSQL作为数据库后端。所以我需要编写为两个数据库运行的代码。

我开始支持MySQL，需要腾出特定的MySQL代码，例如：在迁移中：

public function up() {
    $this->execute('ALTER SCHEMA DEFAULT CHARACTER SET utf8 DEFAULT COLLATE utf8_general_ci');
    $this->execute('ALTER SCHEMA CHARACTER SET utf8 COLLATE utf8_general_ci');
    $this->createTable('user', [ 
            'id' => $this->primaryKey(),
            ... 
        ],
       'CHARACTER SET utf8 COLLATE utf8_general_ci ENGINE=InnoDB'
    );
}

如何重写这段代码？

是否存在解决这个问题的回购？ MySQL和PostgreSQL兼容性的最佳实践是什么？

Answer 1

如果我理解正确您正在讨论编写可以处理特定于数据库的关键字或函数的迁移，具体取决于当前选定的或目标数据库，那么您可能必须为迁移创建自己的逻辑以支持它。

我使用以下类作为基本Migration类，并为tableOptions和drop columns约束扩展此类的迁移。您可以根据需要升级它并添加必要的操作/功能。但它可以创建逻辑来实现您的要求。

<?php

namespace console\migrations;
use Yii;
class Migration extends \yii\db\Migration
{

    /**
     * @var string
     */
    protected $tableOptions;

    /**
     * @var string
     */
    protected $restrict = 'RESTRICT';

    /**
     * @var string
     */
    protected $cascade = 'CASCADE';

    /**
     * @var string
     */
    protected $noAction = 'NO ACTION';

    /**
     * @var mixed
     */
    protected $dbType;

    /**
     * @inheritdoc
     */
    public function init()
    {
        parent::init();

        switch ($this->db->driverName) {
            case 'mysql':
                $this->tableOptions = 'CHARACTER SET utf8 COLLATE utf8_unicode_ci ENGINE=InnoDB';
                $this->dbType = 'mysql';
                break;
            case 'pgsql':
                $this->tableOptions = null;
                $this->dbType = 'pgsql';
                break;
            case 'dblib':
            case 'mssql':
            case 'sqlsrv':
                $this->restrict = 'NO ACTION';
                $this->tableOptions = null;
                $this->dbType = 'sqlsrv';
                break;
            default:
                throw new \RuntimeException('Your database is not supported!');
        }
    }

    /**
     * Drops the constraints for the given column
     *
     * @param string $table  the table name
     * @param string $column the column name
     *
     * @return null
     */
    public function dropColumnConstraints($table, $column)
    {
        $table = Yii::$app->db->schema->getRawTableName($table);
        $cmd = Yii::$app->db->createCommand(
            'SELECT name FROM sys.default_constraints
            WHERE parent_object_id = object_id(:table)
            AND type = \'D\' AND parent_column_id = (
                SELECT column_id
                FROM sys.columns
                WHERE object_id = object_id(:table)
                and name = :column
            )', [':table' => $table, ':column' => $column]
        );

        $constraints = $cmd->queryAll();
        foreach ($constraints as $c) {
            $this->execute('ALTER TABLE ' . Yii::$app->db->quoteTableName($table) . ' DROP CONSTRAINT ' . Yii::$app->db->quoteColumnName($c['name']));
        }
    }

}

Answer 2

我对Postgre并不熟悉，但是通过app-advanced中基本迁移的外观，您可以检查driverName并根据它创建不同的逻辑。

Migration File

$tableOptions = null;
if ($this->db->driverName === 'mysql') {
    $tableOptions = 'CHARACTER SET utf8 COLLATE utf8_unicode_ci ENGINE=InnoDB';
}