Use correct charset/collation from column/table defaults when creating relationships

[ruudk]

Fixes #6823

When you have entities and columns with different charset/collation the SchemaTool should be smart and use the correct charset/collection for the column that references the other table.

In the tests I created the following entities:

User table	Relation	Default charset utf8mb4	Default collation utf8mb4_bin
id		default	default
group_id	References Group table	ascii	ascii_general_ci
status_id	References Status table	latin1	latin1_bin

👉 As you can see, the group_id column uses the charset/collation from the group table default.
For the status_id, it uses the charset/collation from the id column because that was set explicitly.

Group table	_Default charset ascii	_Default collation ascii_general_ci
id	default	default

👉 As you can see, the id column of group uses the table default.

Status table	_Default charset koi8r	_Default collation koi8r_bin
id	latin1	latin1_bin

👉 As you can see, the id column of status is different than the table default.

When I disable the fix in SchemaTool, the following errors would be produced:

// ALTER TABLE user ADD CONSTRAINT FK_8D93D649FE54D947 FOREIGN KEY (group_id) REFERENCES `group` (id)

An exception occurred while executing a query: SQLSTATE[HY000]: General error: 3780 Referencing column 'group_id' and referenced column 'id' in foreign key constraint 'FK_8D93D649FE54D947' are incompatible.

[ruudk]

@greg0ire Ok, the PR is green again 🎉

[greg0ire]

Thanks @ruudk !

[ruudk]

@greg0ire @derrabus ⚠️ Heads up: I'm currently testing 2.12.x in my project and noticed that it produced invalid SQL. So I think we should not tag 2.12.0 yet, before we fix this.

The problem is as follows:
When the JoinColumn is an integer, it should never include charset/collation on the column, as integer columns don't require this.

For example, this SQL was produced:

CREATE TABLE table_name (
  // ..
  user_id INT CHARACTER SET utf8 NOT NULL COLLATE `utf8_unicode_ci`
  // ..
)

resulting in this error:

Query 1 ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CHARACTER SET utf8 NOT NULL COLLATE `utf8_unicode_ci`, type VARCHAR(255) NOT NUL' at line 1

[ruudk]

I think the solution can be simple, never include CHARACTER SET x on the columns. Because this works:

CREATE TABLE table_name (
  // ..
  user_id INT NOT NULL COLLATE `utf8_unicode_ci`,
  string_user_id VARCHAR(255) NOT NULL COLLATE `utf8_unicode_ci`,
  // ..
)

[ruudk]

This should fix the problem: #9652