dynomite product more low-level examples

product.rb

class Product < ApplicationItem
  # field :category,
  #       :product_id,
  #       :product_name,
  #       :price,
  #       :stock_quantity

  field :stock_quantity

  validates :price, presence: true
  before_save :set_stock_quantity

  def set_stock_quantity
    self.stock_quantity ||= 1
  end

  class << self
    # if attribute has index, it must be in **key_condition_expression**
    # works
    def query_gsi_category_and_product_name
      primary_index = indexes.first # category-product_name-index
      query(
        index_name: primary_index.index_name,
        expression_attribute_names: {"#category"=>"category", "#product_name"=>"product_name"},
        expression_attribute_values: {":category"=>"Books", ":product_name"=>"Novel"},
        key_condition_expression: "#category = :category AND #product_name = :product_name",
      ).map(&:product_name)
    end

    # if attribute is primary index, it must be in **key_condition_expression** and no index_name is specified
    # works
    def query_primary_composite_key
      query(
        # index_name: primary_index.index_name, # DO NOT SPECIFY INDEX_NAME for primary key
        expression_attribute_names: {"#category"=>"category", "#product_id"=>"product_id"},
        expression_attribute_values: {":category"=>"Books", ":product_id"=>30},
        key_condition_expression: "#category = :category AND #product_id >= :product_id",
      ).map(&:product_name)
    end

    # Product.where(category: "Books").where("stock_quantity > 30").to_a
    # Product.where(category: "Books").filter_expression("stock_quantity > 30").to_a
    # works
    def query_greather_than
      primary_index = indexes.first
      puts "index_name: #{primary_index.index_name}" # category-product_name-index
      query(
        index_name: primary_index.index_name,
        filter_expression: "#stock_quantity >= :stock_quantity",
        expression_attribute_names: {"#category"=>"category", "#stock_quantity"=>"stock_quantity"},
        expression_attribute_values: {":category"=>"Books", ":stock_quantity"=>30},
        key_condition_expression: "#category = :category",
      ).map(&:product_name)
    end

    # Product.where(product_name: ["Smartphone", "Laptop"]).to_a
    # Product.filter_expression(product_name: ["Smartphone", "Laptop"]).to_a
    # works
    def scan_multiple_product_names
      scan(
        filter_expression: "#product_name IN (:product_name1, :product_name2)",
        expression_attribute_names: {"#product_name"=>"product_name"},
        expression_attribute_values: {":product_name1"=>"Smartphone",":product_name2"=>"Laptop"},
      ).map(&:product_name)
    end

    def query_first
      primary_index = indexes.first
      query(
        index_name: primary_index.index_name,
        :expression_attribute_names=>{"#category"=>"category"},
        :expression_attribute_values=>{":category"=>"Demo"},
        :key_condition_expression=>"#category = :category",
        :table_name=>"demo-dev_products",
        scan_index_forward: true,
      ).first
    end

    def query_last
      primary_index = indexes.first
      query(
        index_name: primary_index.index_name,
        :expression_attribute_names=>{"#category"=>"category"},
        :expression_attribute_values=>{":category"=>"Demo"},
        :key_condition_expression=>"#category = :category",
        :table_name=>"demo-dev_products",
        scan_index_forward: false,
      ).first
    end
  end
end