Rails3 SQLite3 DROP TABLE CASCADE error - ruby-on-rails-3

Question

I have a project on Rails 3.0.2. Its rather big and working well with MySQL database.
But when I try to run it with SQLite database there is an error during migrations:
SQLite3::SQLException: near "CASCADE": syntax error: DROP TABLE "table_name" CASCADE
I searched and found that probably 'PRAGMA foreign_keys = ON' for SQLite will help.
So I have tried to add 'execute("PRAGMA foreign_keys = ON")' in migration right before 'DROP TABLE table_name' but this did not help.
How to turn foreign_keys ON for SQLite in Rails3?
Gems versions
sqlite3 (1.3.6)
sqlite3-ruby (1.3.3)

Answer 1

Here's the syntax diagram for SQLite's DROP TABLE:
In case the image moves, the syntax is like this:
drop table if exists db_name.table_name
where the if exists and db_name. parts are optional. There is no CASCADE in there so SQLite simply doesn't support CASCADE when using DROP TABLE and there's nothing you can do to add it (unless, of course, you want to hack the SQLite C source and add it yourself). You have to accept certain limitations when using SQLite, this is one of them.
If you want to use one migration for both SQLite and MySQL then you'll have to check which database is being used and execute the appropriate SQL or find something that works everywhere (i.e. perform the CASCADE by hand). The easy way to check which database you're using that I can think of right now would be:
case connection
when ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
# PostgreSQL things go here
when ActiveRecord::ConnectionAdapters::AbstractMysqlAdapter
# MySQL things go here
when ActiveRecord::ConnectionAdapters::SQLiteAdapter
# SQLite things go here
...
end