AR::Base の columns から bq で使えるスキーマの json ファイル生成

bq_schema.rb

module BQSchema
  # conversion AR to BQ
  # http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/TableDefinition.html#method-i-column
  # https://cloud.google.com/bigquery/data-types
  def to_bq_schema
    self.columns.map{|c|
    # FIXME decimal and time type conversion
      type = \
        case c.type
        when :integer, :primary_key
          "integer"
        when :decimal
          "integer" # Really?
        when :float
          "float"
        when :string, :text, :time
          "string"
        when :binary
          "bytes"
        when :datetime, :date
          "timestamp"
        when :boolean
          "boolean"
        else
          c.type.to_s
        end

      type = "timestamp" if c.name =~ /_time$/i # FIXME application matter. yield ?

      { name: c.name, type: type }
    }
  end
end

# SomeModel.extend BQSchema
# puts SomeModel.to_bq_schema.to_json

• nullable のような制約について mysql のものを bq にそのまま付けるべきかはやや悩ましいところある
• あと time 列とかを別途追加すべきかとか