问题

I assume that I need to build a native query to truncate a table using Doctine2.

$emptyRsm = new \Doctrine\ORM\Query\ResultSetMapping();
$sql = 'TRUNCATE TABLE Article';
$query = em()->createNativeQuery($sql, $emptyRsm);
$query->execute();

This gives the error

SQLSTATE[HY000]: General error

What do I need to change to my code to make this work?

回答1:

Beware of Truncating Tables

Beware of truncating tables in any RDBMS, especially if you want to use explicit transactions for commit/rollback functionality.

DDL statements perform an implicit-commit

Truncate table statements are data definition language (DDL) statements, and as such truncate table statements trigger an implicit COMMIT to the database upon their execution. If you perform a TABLE TRUNCATE then the database is implicitly committed to--even if the TABLE TRUNCATE is within a START TRANSACTION statement--your table will be truncated and a ROLLBACK will not restore it.

Because truncate table statements perform implicit commits, Maxence's answer does not perform as expected (but it's not wrong, because the question was "how to truncate a table"). His answer does not perform as expected because it truncates the table in a try block, and assumes that the table can be restored in the catch block, if something goes wrong. This is an incorrect assumption.

Other user's comments & experiences in this thread

ChrisAelbrecht was unable to get Maxence's solution to work properly because you cannot rollback a truncate table statement, even if the truncate table statement is in an explicit transaction.

user2130519, unfortunately, was downvoted (-1 until I upvoted) for providing the correct answer--although he did so without justifying his answer, which is like doing math without showing your work.

My recommendation `DELETE FROM`

My recommendation is to use DELETE FROM. In most cases, it will perform as the developer expects. But, DELETE FROM does not come without drawbacks either--you must explicitly reset the auto increment value for the table. To reset the auto increment value for the table, you must use another DDL statement--ALTER TABLE--and, again, don't use ALTER TABLE in your try block. It won't work as expected.

If you want tips on when you should use DELETE FROM vs TRUNCATE see Pros & Cons of TRUNCATE vs DELETE FROM.

If you really must, here's how to truncate

Now, with all that said. If you really want to truncate a table using Doctrine2, use this: (Below is the portion of Maxence's answer that correctly truncates a table)

$cmd = $em->getClassMetadata($className);
$connection = $em->getConnection();
$dbPlatform = $connection->getDatabasePlatform();
$connection->query('SET FOREIGN_KEY_CHECKS=0');
$q = $dbPlatform->getTruncateTableSql($cmd->getTableName());
$connection->executeUpdate($q);
$connection->query('SET FOREIGN_KEY_CHECKS=1');

How to delete a table with rollback/commit functionalty.

But, if you want rollback/commit functionality, you must use DELETE FROM: (Below is a modified version of Maxence's answer.)

$cmd = $em->getClassMetadata($className);
$connection = $em->getConnection();
$connection->beginTransaction();

try {
    $connection->query('SET FOREIGN_KEY_CHECKS=0');
    $connection->query('DELETE FROM '.$cmd->getTableName());
    // Beware of ALTER TABLE here--it's another DDL statement and will cause
    // an implicit commit.
    $connection->query('SET FOREIGN_KEY_CHECKS=1');
    $connection->commit();
} catch (\Exception $e) {
    $connection->rollback();
}

If you need to reset the auto increment value, remember to call ALTER TABLE <tableName> AUTO_INCREMENT = 1.

回答2:

Here is the code I'm using:

$cmd = $em->getClassMetadata($className);
$connection = $em->getConnection();
$dbPlatform = $connection->getDatabasePlatform();
$connection->beginTransaction();
try {
    $connection->query('SET FOREIGN_KEY_CHECKS=0');
    $q = $dbPlatform->getTruncateTableSql($cmd->getTableName());
    $connection->executeUpdate($q);
    $connection->query('SET FOREIGN_KEY_CHECKS=1');
    $connection->commit();
}
catch (\Exception $e) {
    $connection->rollback();
}

回答3:

Or you could just try this:

$this->getEm()->createQuery('DELETE AcmeBundle:Post p')->execute();

If you have relations you should be careful to handle the linked entities.

回答4:

This is example truncating method from trait in unit tests.

/**
 * Cleanup any needed table abroad TRUNCATE SQL function
 *
 * @param string $className (example: App\Entity\User)
 * @param EntityManager $em
 * @return bool
 */
private function truncateTable (string $className, EntityManager $em): bool {
    $cmd = $em->getClassMetadata($className);
    $connection = $em->getConnection();
    $connection->beginTransaction();

    try {
        $connection->query('SET FOREIGN_KEY_CHECKS=0');
        $connection->query('TRUNCATE TABLE '.$cmd->getTableName());
        $connection->query('SET FOREIGN_KEY_CHECKS=1');
        $connection->commit();
        $em->flush();
    } catch (\Exception $e) {
        try {
            fwrite(STDERR, print_r('Can\'t truncate table ' . $cmd->getTableName() . '. Reason: ' . $e->getMessage(), TRUE));
            $connection->rollback();
            return false;
        } catch (ConnectionException $connectionException) {
            fwrite(STDERR, print_r('Can\'t rollback truncating table ' . $cmd->getTableName() . '. Reason: ' . $connectionException->getMessage(), TRUE));
            return false;
        }
    }
    return true;
}

Please note, that if you do not use $em->flush(), you have a risk to have a problem with next query to doctrine.

Also you must understand, that if you use this method in a controller, you must change the lines fwrite(STDERR, print_r(... to something your logger service can use.

来源：https://stackoverflow.com/questions/9686888/how-to-truncate-a-table-using-doctrine-2

标签

php

mysql

doctrine-orm

nativequery

How to truncate a table using Doctrine 2?

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