How can I force the rails SQL cache to clear?

Question

I am running rails db:reset db:migrate in between tests from within my testing script (which imports and interfaces with the model directly), but the changes are not reflected between the first test and the second test. More specifically, the changes caused by the first test are not reversed as they should be.

When I connect to the database externally (from the shell), I observe that the command has taken effect.

I have already looked at this question but the solution had no effect (quite literally, there was no error but also no discernible effect).

How can I force my test script to clear its in-memory cache of the sqlite state?

---

Full steps for reproducing the problem.

1. Create a new rails app.

    rails new MWE 

2. Put the following in db/schema.rb

    ActiveRecord::Schema.define(version: 20140408213603) do create_table "users", force: true do |t| t.string "username" end end 

3. Put the following in db/seed.rb .

    User.create(username: 'user1') User.create(username: 'user2') User.create(username: 'user3') 

4. Put the following in the Gemfile .

    source 'https://rubygems.org' gem 'rails', '4.0.0' gem 'sqlite3' gem 'protected_attributes' 

5. Put the following in a file called app/models/user.rb .

    class User < ActiveRecord::Base attr_accessible :username end 

6. Run the following commands.

    bundle install rake db:reset 

7. Place the following contents in a file called MWE.rb

    load 'config/application.rb' load 'config/environment.rb' load 'app/models/user.rb' # Mimic the unsafe call in the source code system("bundle exec rake db:reset") puts User.count User.destroy_all("username = 'user3'") puts User.count system("bundle exec rake db:reset") puts User.count User.destroy_all("username = 'user3'") puts User.count 

8. Run the file and observe actual output .

    $ ruby MWE.rb -- create_table("users", {:force=>true}) -> 0.0362s -- initialize_schema_migrations_table() -> 0.0248s 3 2 -- create_table("users", {:force=>true}) -> 0.0809s -- initialize_schema_migrations_table() -> 0.0490s 2 2 

Desired Output

    -- create_table("users", {:force=>true})
       -> 0.0362s
    -- initialize_schema_migrations_table()
       -> 0.0248s
    3
    2
    -- create_table("users", {:force=>true})
       -> 0.0809s
    -- initialize_schema_migrations_table()
       -> 0.0490s
    3
    2

How can I force the DB reset to be reflected in the model?

Answer 1

All you need to do is to reestablish database connection. Try:

system("bundle exec rake db:reset")
puts User.count
User.destroy_all("username = 'user3'")
puts User.count

system("bundle exec rake db:reset")
ActiveRecord::Base.clear_all_connections!
puts User.count
User.destroy_all("username = 'user3'")
puts User.count

The main question is: why do you need to do this? I am pretty certain there is a better way to achieve what you want.