Maybe/app/models/income_statement/totals.rb

class IncomeStatement::Totals
  def initialize(family, transactions_scope:)
    @family = family
    @transactions_scope = transactions_scope
  end

  def call
    ActiveRecord::Base.connection.select_all(query_sql).map do |row|
      TotalsRow.new(
        parent_category_id: row["parent_category_id"],
        category_id: row["category_id"],
        classification: row["classification"],
        total: row["total"],
        transactions_count: row["transactions_count"]
      )
    end
  end

  private
    TotalsRow = Data.define(:parent_category_id, :category_id, :classification, :total, :transactions_count)

    def query_sql
      ActiveRecord::Base.sanitize_sql_array([
        optimized_query_sql,
        sql_params
      ])
    end

    # OPTIMIZED: Direct SUM aggregation without unnecessary time bucketing
    # Eliminates CTE and intermediate date grouping for maximum performance
    def optimized_query_sql
      <<~SQL
        SELECT
          c.id as category_id,
          c.parent_id as parent_category_id,
          CASE WHEN ae.amount < 0 THEN 'income' ELSE 'expense' END as classification,
          ABS(SUM(ae.amount * COALESCE(er.rate, 1))) as total,
          COUNT(ae.id) as transactions_count
        FROM (#{@transactions_scope.to_sql}) at
        JOIN entries ae ON ae.entryable_id = at.id AND ae.entryable_type = 'Transaction'
        LEFT JOIN categories c ON c.id = at.category_id
        LEFT JOIN exchange_rates er ON (
          er.date = ae.date AND
          er.from_currency = ae.currency AND
          er.to_currency = :target_currency
        )
        WHERE at.kind NOT IN ('funds_movement', 'one_time', 'cc_payment')
          AND ae.excluded = false
        GROUP BY c.id, c.parent_id, CASE WHEN ae.amount < 0 THEN 'income' ELSE 'expense' END;
      SQL
    end

    def sql_params
      {
        target_currency: @family.currency
      }
    end
end