JSON column for flexible schema extensions

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                  class AddMetadataToUsers < ActiveRecord::Migration[6.1]
  def change
    add_column :users, :metadata, :jsonb, default: {}, null: false
    add_index :users, :metadata, using: :gin
  end
end

                  class User < ApplicationRecord
  store_accessor :metadata, :theme, :timezone, :email_notifications, :beta_features

  # Query users with specific metadata values
  scope :with_beta_features, -> { where("metadata @> ?", { beta_features: true }.to_json) }
  scope :in_timezone, ->(tz) { where("metadata->>'timezone' = ?", tz) }

  # Default values
  after_initialize do
    self.metadata ||= {}
    self.theme ||= 'light'
    self.timezone ||= 'UTC'
    self.email_notifications = true if email_notifications.nil?
  end
end

                  module Api
  module V1
    class UserPreferencesController < BaseController
      before_action :authenticate_user!

      def update
        current_user.update!(preference_params)
        render json: { metadata: current_user.metadata }, status: :ok
      end

      private

      def preference_params
        params.require(:preferences).permit(:theme, :timezone, :email_notifications, beta_features: [])
      end
    end
  end
end

PostgreSQL's jsonb columns provide schema flexibility for semi-structured data without sacrificing query performance. I use JSON columns for user preferences, feature flags, or metadata that varies by record type. Unlike traditional EAV patterns, jsonb supports indexing and efficient queries via GIN indexes and operators like @> (contains) or -> (extract). The store_accessor method creates virtual attributes that feel like regular columns while being stored in the JSON field. This approach balances structure and flexibility—core attributes remain as columns for performance and integrity, while optional or variable attributes live in JSON. The downside is reduced type safety and schema enforcement compared to dedicated columns.

Alex Kumar

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JSON column for flexible schema extensions

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