Module: RailsOnPg::ForeignKeys

Defined in:
lib/rails_on_pg/foreign_keys.rb

Instance Method Summary collapse

Instance Method Details

#add_foreign_key(from_table, from_column, to_table, options = {}) ⇒ Object

Define new foreign key Example:

add_foreign_key :order_items,:product_id,:orders

where orders is orders is referenced table and order_items is referencing table foreign key will be: ‘fk_order_items_product_id’ optional options: 

<tt>:on_delete</tt>
<tt>:on_update</tt>
<tt>:column</tt>



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# File 'lib/rails_on_pg/foreign_keys.rb', line 13

def add_foreign_key(from_table, from_column, to_table, options={})
  # default delete and on update actions
  options.reverse_merge!({:on_delete=>'NO ACTION', :on_update=>'NO ACTION',:column=>'id'})
  constraint_name = "fk_#{from_table}_#{from_column}"

  execute %{ALTER TABLE #{from_table}
            ADD CONSTRAINT #{constraint_name}
            FOREIGN KEY (#{from_column})
            REFERENCES #{to_table}(#{options[:column]}) 
            ON UPDATE #{options[:on_update]} 
            ON DELETE #{options[:on_delete]} }
end

#remove_foreign_key(from_table, from_column, to_table) ⇒ Object

Remove prev created key



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# File 'lib/rails_on_pg/foreign_keys.rb', line 27

def remove_foreign_key(from_table, from_column, to_table)
  constraint_name = "fk_#{from_table}_#{from_column}"
  # check if constraint already exist
  count = ActiveRecord::Base.connection.select_value("select count(1) from pg_constraint where conname='#{constraint_name}'")

  unless count.to_i == 0
    execute %{ALTER TABLE #{from_table} DROP CONSTRAINT #{constraint_name}}
  end
end