Rails给关系表带来问题，SQLite3 :: SQLException：没有这样的列

Question

Can't seem to find a solution to this one. I have a relational table, BlabsUser, from which I'm trying to find and destroy a record. I'm doing this:

BlabsUser.find_by_user_id_and_blab_id(1,29).destroy

And getting this lovely error:

BlabsUser Load (0.2ms)  SELECT "blabs_users".* FROM "blabs_users" WHERE "blabs_users"."user_id" = 1 AND "blabs_users"."blab_id" = 29 LIMIT 1
Could not log "sql.active_record" event. NoMethodError: undefined method `name' for nil:NilClass
SQLite3::SQLException: no such column: blabs_users.: DELETE FROM "blabs_users" WHERE "blabs_users"."" = ?
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: blabs_users.: DELETE FROM "blabs_users" WHERE "blabs_users"."" = ?
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/sqlite3-1.3.5/lib/sqlite3/database.rb:91:in `initialize'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/sqlite3-1.3.5/lib/sqlite3/database.rb:91:in `new'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/sqlite3-1.3.5/lib/sqlite3/database.rb:91:in `prepare'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/connection_adapters/sqlite_adapter.rb:234:in `block in exec_query'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/connection_adapters/abstract_adapter.rb:244:in `block in log'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.1.3/lib/active_support/notifications/instrumenter.rb:21:in `instrument'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/connection_adapters/abstract_adapter.rb:239:in `log'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/connection_adapters/sqlite_adapter.rb:223:in `exec_query'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/connection_adapters/sqlite_adapter.rb:249:in `exec_delete'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/connection_adapters/abstract/database_statements.rb:101:in `delete'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/connection_adapters/abstract/query_cache.rb:14:in `delete'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/relation.rb:351:in `delete_all'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/persistence.rb:94:in `destroy'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/locking/optimistic.rb:119:in `destroy'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/callbacks.rb:254:in `block in destroy'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.1.3/lib/active_support/callbacks.rb:390:in `_run_destroy_callbacks'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.1.3/lib/active_support/callbacks.rb:81:in `run_callbacks'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/callbacks.rb:254:in `destroy'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/transactions.rb:236:in `block in destroy'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/transactions.rb:295:in `block in with_transaction_returning_status'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/connection_adapters/abstract/database_statements.rb:192:in `transaction'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/transactions.rb:208:in `transaction'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/transactions.rb:293:in `with_transaction_returning_status'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.1.3/lib/active_record/transactions.rb:236:in `destroy'
    from (irb):1
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.3/lib/rails/commands/console.rb:45:in `start'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.3/lib/rails/commands/console.rb:8:in `start'
    from /Users/dylandrop/.rvm/gems/ruby-1.9.2-p290/gems/railties-3.1.3/lib/rails/commands.rb:40:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'

Why is it looking for a column called blabs_users? Why isn't it just looking for a record in my blabs_users table? Also, more importantly, how do I fix this?

And I've also tried this with the same problem:

BlabsUser.destroy_all(:blab_id => 29, :user_id => 1)

My model is just

class BlabsUser < ActiveRecord::Base
end

Migration is just

class BlabsUsers < ActiveRecord::Migration
  def self.up
      create_table :blabs_users, :id => false, :force => true do |t|
          t.integer :user_id
          t.integer :blab_id
          t.timestamps
      end
  end

  def self.down
      drop_table :blabs_users
  end
end

Answer 1

ActiveRecord depends pretty heavily on having a unique key to work with (usually the primary key of the table) Since you explicitly don't have one defined ( :id => false ), I strongly suspect that your problem is related to that.

destroy() is also documented as Destroy an object (or multiple objects) that has the given id which strongly suggests it needs that unique id to work with.