Reduce column size to fit utf8mb4 index

[foaly-nr1]

As you set an index on the name and ownerId properties of your Entity, creation of the tables fails in an utf8mb4 database:

[Doctrine\DBAL\Exception\DriverException]                                                                                                                                                                                         
  An exception occurred while executing 'CREATE TABLE dmishh_settings (id INT AUTO_INCREMENT NOT NULL, name VARCHAR(255) NOT NULL, value LONGTEXT DEFAULT NULL, owner_id VARCHAR(255) DEFAULT NULL, INDEX name_owner_id_idx (name,  
   owner_id), PRIMARY KEY(id)) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci ENGINE = InnoDB':                                                                                                                           
  SQLSTATE[HY000]: General error: 1709 Index column size too large. The maximum column size is 767 bytes.

The reason can be found in the MySQL 5.7 upgrade notes:

InnoDB has a maximum index length of 767 bytes for tables that use a COMPACT or REDUNDANT row format, so for utf8 or utf8mb4 columns, you can index a maximum of 255 or 191 characters, respectively. If you currently have utf8 columns with indexes longer than 191 characters, you will need to index a smaller number of characters.

This pull request reduces the column sizes to support utf8mb4.

[rvanlaak]

I think Doctrine should be the one to manage length of such fields, @Nyholm can you validate that we can just remove the length parameter of the annotation?

[Nyholm]

It is a huge BC break to reduce the size of the field. We can not merge the PR as it is.
When using a plain old MySQL database utf8 we can simply remove the length parameter because MySQL (not Doctrine) will default it to 255. I do not know the behavior with utf8mb4. @foaly-nr1 please try to remove it and see if that solves your problem. If so, we are happy to merge this PR.

For the record: I believe Symfony best practice for 3rd party bundles states that we should not use annotations when defining the database mapping. If we use XML or Yaml one could override our mapping with their own.

[foaly-nr1]

Let me check, that'd be an ideal solution.

@Nyholm I don't believe that's the case:

Due to the way Doctrine works, it is not possible to override entity mapping of a bundle. However, if a bundle provides a mapped superclass (such as the User entity in the FOSUserBundle) one can override attributes and associations. Learn more about this feature and its limitations in the Doctrine documentation.

– http://symfony.com/doc/current/cookbook/bundles/override.html

[Nyholm]

I don't believe that's the case:

Hm, interesting. I thought one could just override the mapping configuration file like you normally would. I'll have to investigate in that further then.. Thank you for the resource.

[foaly-nr1]

Unlucky, Doctrine doesn't handle it correctly. I will open a ticket with them, but doubt they will want to move away from a simple default value.

[Nyholm]

I think it's more of an issue with Symfony. Symfony should make sure to use the use the config file in app/Resources/OtherBundle/config/doctrine/mapping.yml instead of OtherBundle/config/doctrine/mapping.yml

[rvanlaak]

Also had problems with overriding the length of a field in another bundle, which is not possible because the configs are not merged. See craue/CraueConfigBundle#20

[foaly-nr1]

I know we're already at 2.0.0-beta4 so this might be too late. But generally, we could sneak a breaking change into this major release?

[foaly-nr1]

Ping @Nyholm breaking change in 2.0.0?