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@@ -522,6 +522,26 @@ module ThoughtBot # :nodoc:
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           end
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         end
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       end
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+
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+      # Ensures that there are DB indices on the given columns or tuples of columns.
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+      # Also aliased to should_have_index for readability
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+      #   
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+      #   should_have_indices :email, :name, [:commentable_type, :commentable_id]
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+      #   should_have_index :age
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+      #
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+      def should_have_indices(*columns)
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+        table = model_class.name.tableize
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+        indices = ::ActiveRecord::Base.connection.indexes(table).map(&:columns)
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+
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+        columns.each do |column|
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+          should "have index on #{table} for #{column.inspect}" do
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+            columns = [column].flatten.map(&:to_s)
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+            assert_contains(indices, columns)
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+          end
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+        end
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+      end
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+
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+      alias_method :should_have_index, :should_have_indices
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       # Ensures that the model cannot be saved if one of the attributes listed is not accepted.
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       #

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@@ -5,6 +5,10 @@ class CreateUsers < ActiveRecord::Migration
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       t.column :email, :string
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       t.column :age, :integer
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     end
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+    add_index :users, :email
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+    add_index :users, :name
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+    add_index :users, :age
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+    add_index :users, [:email, :name]
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   end
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   def self.down

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@@ -8,6 +8,9 @@ class UserTest < Test::Unit::TestCase
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   should_have_one :address
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+  should_have_indices :email, :name, [:email, :name]
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+  should_have_index :age
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+
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   should_not_allow_values_for :email, "blah", "b lah"
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   should_allow_values_for :email, "a@b.com", "asdf@asdf.com"
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   should_ensure_length_in_range :email, 1..100