aggregation

class Tag < ApplicationRecord
  has_many :taggings, dependent: :destroy

  scope :top, ->(limit = 20) {
    joins(:taggings)
      .group(Arel.sql("tags.id"))

-- ROW_NUMBER: Unique sequential number
SELECT
  name,
  department,
  salary,
  ROW_NUMBER() OVER (ORDER BY salary DESC) as overall_rank,

@Component
public class SalesRollupScheduler {

    private static final Logger log = LoggerFactory.getLogger(SalesRollupScheduler.class);
    private static final int ROLLUP_WINDOW_DAYS = 3;

CREATE TABLE daily_metrics (
    id          BIGGENERATED ALWAYS AS IDENTITY PRIMARY KEY,
    tenant_id   BIGINT      NOT NULL,
    metric      TEXT        NOT NULL,
    day         DATE        NOT NULL,
    count       BIGINT      NOT NULL DEFAULT 0,

use chrono::NaiveDate;
use rust_decimal::Decimal;
use serde::{Deserialize, Deserializer};

#[derive(Debug, Clone, Deserialize)]
pub struct Transaction {

class ReportsController < ApplicationController
  def monthly_sales
    year = params.fetch(:year, Date.current.year).to_i
    rows = Order.monthly_sales(year: year)
    @report = MonthlySalesReport.new(rows, year: year)

import threading


class MinuteRingBuffer:
    def __init__(self, window_minutes=15):
        if window_minutes < 1:

-- ROLLUP for hierarchical subtotals
SELECT
  COALESCE(category, 'ALL CATEGORIES') AS category,
  COALESCE(subcategory, 'ALL SUBCATEGORIES') AS subcategory,
  SUM(revenue) AS total_revenue,
  COUNT(*) AS order_count