Active Record batch_insert

batch_insert.rb

# Add batch insert functionality to the model.
# 
# Example:
#
#    class User < ActiveRecord::Base
#      include PgBatchInsert
#    end
#
#    User.pg_batch_insert(
#      %w[name email],
#      [
#        ["Jack", "jack@rails.dev"],
#        ["Alice", "alice@rails.dev"]
#      ]
#    )
module PgBatchInsert
  extend ActiveSupport::Concern

  module ClassMethods
    def pg_batch_insert(attributes, data, on_conflict: nil, returning: nil)
      raise ArgumentError, "Values must not be empty" if data.empty?

      columns = columns_for_attributes(attributes)

      fields_str = quote_column_names(columns)
      values_str = quote_many_records(columns, data)

      sql = <<~SQL
        INSERT INTO #{quoted_table_name}
        (#{fields_str})
        VALUES #{values_str}
      SQL

      unless on_conflict.nil?
        on_conflict = "DO NOTHING" if on_conflict == :skip
        sql += " ON CONFLICT #{on_conflict}"
      end
          
      unless returning.nil?
        sql += " RETURNING #{returning}"
      end

      connection.execute(sql)
    end
      
    def columns_for_attributes(attributes)
      attributes.map do |attribute|
        column_for_attribute(attribute)
      end
    end

    def quote_column_names(columns)
      columns.map do |column|
        connection.quote_column_name(column.name)
      end.join(",")
    end

    def quote_record(columns, record_values)
      values_str = record_values.each_with_index.map do |value, i|
        type = connection.lookup_cast_type_from_column(columns[i])
        connection.quote(type.serialize(value))
      end.join(",")
      "(#{values_str})"
    end

    def quote_many_records(columns, data)
      data.map { |values| quote_record(columns, values) }.join(",")
    end
  end
end