Aggregation Pipeline — مستوى متقدم

db.orders.aggregate([
  { $facet: {
    totalStats: [{ $group: { _id: null, total: { $sum: "$total" } }}],
    byStatus: [{ $group: { _id: "$status", count: { $sum: 1 } }}],
    topCustomers: [
      { $group: { _id: "$customerId", total: { $sum: "$total" } }},
      { $sort: { total: -1 }},
      { $limit: 5 }
    ]
  }}
])

db.orders.aggregate([
  { $bucket: {
    groupBy: "$total",
    boundaries: [0, 50, 100, 200, 500, 1000],
    default: "1000+",
    output: {
      count: { $sum: 1 },
      orders: { $push: { id: "$_id", customer: "$customerId" }}
    }
  }}
])

// غير محسَّن
db.orders.aggregate([
  { $group: { _id: "$customerId", count: { $sum: 1 } }},
  { $match: { count: { $gt: 5 } }},
  { $sort: { count: -1 }}
])

// محسَّن
db.orders.aggregate([
  { $match: { status: "completed" }},  // فلترة مبكرة
  { $sort: { createdAt: -1 }},         // استخدام index
  { $group: { _id: "$customerId", count: { $sum: 1 } }},
  { $match: { count: { $gt: 5 }}}
])

db.orders.aggregate([
  { $match: { status: "completed" }},
  { $limit: 1000 },
  { $group: { _id: "$customerId", total: { $sum: "$total" } }}
])

db.orders.aggregate([
  { $match: { status: "completed", createdAt: { $gte: ISODate("2024-01-01") }}},
  { $lookup: {
    from: "customers",
    localField: "customerId",
    foreignField: "_id",
    as: "customer"
  }},
  { $unwind: "$customer" },
  { $lookup: {
    from: "products",
    localField: "items.productId",
    foreignField: "_id",
    as: "products"
  }},
  { $group: {
    _id: "$customer.email",
    customerName: { $first: "$customer.name" },
    totalSpent: { $sum: "$total" },
    productCount: { $sum: { $size: "$items" }}
  }},
  { $sort: { totalSpent: -1 }},
  { $limit: 10 },
  { $project: {
    _id: 0,
    customerName: 1,
    email: "$_id",
    totalSpent: { $round: ["$totalSpent", 2] },
    productCount: 1
  }}
])