Module: DbAgile::Core::Schema::Computations::Merge

Included in:
DbAgile::Core::Schema::Computations
Defined in:
lib/dbagile/core/schema/computations/merge.rb

Instance Method Summary collapse

Instance Method Details

#merge(left, right, builder, &block) ⇒ Object

Computes set difference between schemas.



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# File 'lib/dbagile/core/schema/computations/merge.rb', line 8

def merge(left, right, builder, &block)
  unless left.class == right.class
    raise ArgumentError, "#{left.class} != #{right.class}"
  end
  unless left.composite?
    raise ArgumentError, "Diff called on a part object!"
  end
  
  # Computes key differences
  left_keys, right_keys = left.part_keys, right.part_keys
  left_only  = left_keys - right_keys
  right_only = right_keys - left_keys
  commons    = left_keys & right_keys 
  
  mine = Schema::NO_CHANGE
  builder.send(left.builder_handler, *left.builder_args){|builder_object|
    left_only.each {|key| 
      mine = Schema::TO_ALTER
      builder_object.[]=(key, left[key].dup, Schema::TO_DROP)
    }
    right_only.each{|key| 
      mine = Schema::TO_ALTER
      builder_object.[]=(key, right[key].dup, Schema::TO_CREATE)
    }
    commons.each{|key|
      on_left, on_right = left[key], right[key]
      if on_left.composite?
        recursed = merge(on_left, on_right, builder, &block).status
        mine = Schema::TO_ALTER if recursed != Schema::NO_CHANGE
      elsif on_left.look_same_as?(on_right)
        builder_object.[]=(key, left[key].dup, Schema::NO_CHANGE)
      elsif block
        resolved = block.call(on_left, on_right)
        if resolved
          builder_object.[]=(key, resolved, Schema::TO_ALTER)
        end
      end
    }
    builder_object.status = mine
  }
end