greenDAO not generating FOREIGN KEY(...) constraint in table

Question

When I create a bidirectional 1:n relationship as shown below, the generator does not use any FOREIGN KEY(...) constraints on the table.

entity customer = schema.addEntity("Customer");
customer.addIdProperty();
customer.addStringProperty("name").notNull();

Entity order = schema.addEntity("Order");
order.setTableName("ORDERS"); // "ORDER" is a reserved keyword
order.addIdProperty();
Property orderDate = order.addDateProperty("date").getProperty();
Property customerId = order.addLongProperty("customerId").notNull().getProperty();
order.addToOne(customer, customerId);

customer.addToMany(order, customerId);

Is this normal? Is it supposed to generate FOREIGN KEY(...) constraints in the table or is it only enforced at runtime through code?

Answer 1

I was stuck at the same issue while working on a project.

Going through the generated code by DaoGenerator, foreign key constraints are not generated even with the use of ToMany relation.

I tried appending the foreign key constraint manually in the query in each entity DAO, and yet it didn't solve the issue.

Referring the sqlite documentation, I found that the foreign key is not enforced by-default. You have to run query PRAGMA foreign_keys = ON; for every connection created to database. I verified it from adb shell. Foreign key was enforced after running PRAGMA query.

Last problem was to find a place for this code in project so that it will execute for every session.

Solution is in DaoSession class generated by the DaoGenerator project

insert

 if(!db.isReadOnly()){
     db.execSQL("PRAGMA foreign_keys = ON;");
 }

at the end of the constructor.

Don't forget to manually add foreign key constraint in create table queries for each DAO having foreign key property.