It seems that the symfony generator needs a primary key. If there’s no PK defined the generator throws the following exception:
symfony generator Invalid column name ‘id’
In some blog post they solved the problem by adding a primary key to the concerning table. But in my case the DB isn’t under my control, so I found out that it is enough to set the primary key only in the schema.
my_table: connection: doctrine tableName: MyTable columns: id: type: int(11) primary: true # <-- SET TO true