Symfony2 DBAL Update method returning 0 - mysql

Question

I'm getting a strange result, where an update method (http://docs.doctrine-project.org/projects/doctrine-dbal/en/latest/reference/data-retrieval-and-manipulation.html#update) call that activates/deactivates site users accounts in my mySQL database sometimes are not updated and returns a 0. Here is the code:
$user_id = '198';
$sqlSetStmnt= [ 'activation_code' => NULL, 'active' => 0 ];
$conn = $this->get( 'database_connection' );
try {
$result = $conn->update( 'users', $sqlSetStmnt,[ 'id' => (int)$user_id ] );
}
catch( Exception $e ) {
$error = $e->getMessage();
throw new \Exception( 'update user account data function -- ' .
'error: ' . $error . ' - ' .
'unable to update your account!' );
} // End of catch( Exception ) block.
if( ( $result === FALSE ) || ( $result !== 1 ) ) {
throw new \Exception( 'update user account data function -- ' .
'update return value: ' . $result . ' - ' .
'unable to update your account!' );
} // if( ( $result === FALSE ) || ( $result !== 1 ) ) ...
The users table has an id int(11) column which is the primary key, an active tinyint(1) column, and activation_code varchar(40) NULL column.
Please note the $user_id variable contains a string value of '198', but it is cast to an int when creating the $sqlSetStmnt value.
Inspecting the users table confirms that there was a row in the users table with the id column value of 198 at the time of the update call.
The account used when running the update call has enough privileges to change the row active and activation_code column values.
There are no other users in the system or accessing the database, so there aren't any locks on the row.
I inspected the code using x-debug, and the values of the $user_id and $sqlSetStmnt variables were properly set to the values that I expected, that $result was set to 0 by the update method, and that no exceptions were thrown by the update method call.
By the way, there is no need to using variable binding because the values in the $user_id and $sqlSetStmnt variables are not input by an user, so no possibility of SQL-Injection, or Buffer-Overrun.
Is there some way to get information from DBAL about why the update method returned 0?
Thank you.

Answer 1

Before solving this issue I switched from:
$result = $conn->update( 'users', $sqlSetStmnt, [ 'id' => (int)$user_id ] );
to:
$sqlUpdateStmnt = 'UPDATE `users` SET field = value ' .
'WHERE `id` = ' . $user_id;
$result = $conn->executeUpdate( $sqlUpdateStmnt );
and got exactly the same result, where some updates would return 0 rows when there definitely was a row in the users table with an id matching the value of $user_id.
I got around this problem by fetching the existing row and then only updating the row when the fields in the set-clause were different than the same columns from the table.
This tells me that the 0 return value wasn't that there were no matching rows, but that the updated didn't have any effect on any rows.
So this issue isn't a bug, so much as a misunderstanding of the result. However, the problem still exists when using the update() method of how to determine when the update failed due to no matching rows and when no changes were made.
The solution that I ended up solves this at the cost of a pre-fetch to verify that the update would affect a row. In my case, with a multi-user database application, pre-fetching isn't actually a problem because the row that is to be updated could have been deleted by another user before the update tries to make its change. But, it would be nice if both update methods explained this more clearly, and returned different values: 0 for no affected rows and FALSE for no rows found.