$skip

Vous utilisez l’étape $skip du pipeline d’agrégation pour ignorer un nombre spécifié de documents de l’entrée et transmettre les documents restants à l’étape suivante du pipeline. La phase est utile pour implémenter la pagination dans les requêtes et contrôler le sous-ensemble de documents sur lesquels les étapes suivantes du pipeline fonctionnent.

Syntaxe

{
  $skip: <number>
}

Paramètres

Paramètre	Descriptif
number	Nombre de documents à ignorer avant de transmettre les documents restants à la phase suivante.

Examples

Considérez cet exemple de document de la collection des magasins.

{
    _id: '0fcc0bf0-ed18-4ab8-b558-9848e18058f4',
    name: 'First Up Consultants | Beverage Shop - Satterfieldmouth',
    location: { lat: -89.2384, lon: -46.4012 },
    staff: { employeeCount: { fullTime: 2, partTime: 20 } },
    sales: {
      salesByCategory: [
        { categoryName: 'Wine Accessories', totalSales: 34450 },
        { categoryName: 'Bitters', totalSales: 39496 },
        { categoryName: 'Rum', totalSales: 1734 }
      ],
      revenue: 75670
    },
    promotionEvents: [
      {
        eventName: 'Unbeatable Bargain Bash',
        promotionalDates: {
          startDate: { Year: 2024, Month: 6, Day: 23 },
          endDate: { Year: 2024, Month: 7, Day: 2 }
        },
        discounts: [
          { categoryName: 'Whiskey', discountPercentage: 7 },
          { categoryName: 'Bitters', discountPercentage: 15 },
          { categoryName: 'Brandy', discountPercentage: 8 },
          { categoryName: 'Sports Drinks', discountPercentage: 22 },
          { categoryName: 'Vodka', discountPercentage: 19 }
        ]
      },
      {
        eventName: 'Steal of a Deal Days',
        promotionalDates: {
          startDate: { Year: 2024, Month: 9, Day: 21 },
          endDate: { Year: 2024, Month: 9, Day: 29 }
        },
        discounts: [
          { categoryName: 'Organic Wine', discountPercentage: 19 },
          { categoryName: 'White Wine', discountPercentage: 20 },
          { categoryName: 'Sparkling Wine', discountPercentage: 19 },
          { categoryName: 'Whiskey', discountPercentage: 17 },
          { categoryName: 'Vodka', discountPercentage: 23 }
        ]
      },
      {
        eventName: 'Summer Sale',
        promotionalDates: {
          startDate: { Year: 2024, Month: 6, Day: 1 },
          endDate: { Year: 2024, Month: 6, Day: 15 }
        },
        discounts: [ { categoryName: 'DJ Speakers', discountPercentage: 20 } ]
      }
    ],
    company: 'First Up Consultants',
    city: 'Satterfieldmouth',
    storeOpeningDate: ISODate("2024-09-20T18:28:57.302Z"),
    lastUpdated: Timestamp({ t: 1729448937, i: 1 }),
    store: { promotionEvents: null },
    tag: [ '#ShopLocal' ]
  }

Exemple 1 : Ignorer les documents d’une collection

Pour ignorer les 2 premiers documents et retourner le reste, vous pouvez utiliser le pipeline d’agrégation suivant :

db.stores.aggregate([
  { $skip: 2 }
])

Les deux premiers résultats retournés par cette requête sont les suivants :

[
  {
    "_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5",
    "store": {
      "name": "Downtown Store",
      "promotionEvents": ["Summer Sale", "Black Friday", "Holiday Deals"]
    }
  },
  {
    "_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c6",
    "store": {
      "name": "Uptown Store",
      "promotionEvents": ["Back to School", "Winter Sale"]
    }
  }
]

Exemple 2 : Ignorer les documents, puis limiter le résultat

Pour ignorer les 2 premiers documents, puis limiter le résultat aux 3 documents suivants, vous pouvez associer $skip à $limit :

db.stores.aggregate([
  { $skip: 2 },
  { $limit: 3 }
])

Les deux premiers résultats retournés par cette requête sont les suivants :

[
    {
        "_id": "728c068a-638c-40af-9172-8ccfa7dddb49",
        "name": "Contoso, Ltd. | Book Store - Lake Myron",
        "location": {
            "lat": 29.416,
            "lon": 21.5231
        },
        "staff": {
            "employeeCount": {
                "fullTime": 7,
                "partTime": 16
            }
        },
        "sales": {
            "salesByCategory": [
                {
                    "categoryName": "Science Fiction",
                    "totalSales": 34879
                }
            ],
            "revenue": 34879
        },
        "promotionEvents": [
            {
                "eventName": "Blowout Bonanza",
                "promotionalDates": {
                    "startDate": {
                        "Year": 2024,
                        "Month": 9,
                        "Day": 21
                    },
                    "endDate": {
                        "Year": 2024,
                        "Month": 9,
                        "Day": 30
                    }
                },
                "discounts": [
                    {
                        "categoryName": "Children's Books",
                        "discountPercentage": 11
                    },
                    {
                        "categoryName": "Fiction",
                        "discountPercentage": 21
                    }
                ]
            }
        ],
        "company": "Contoso, Ltd.",
        "city": "Lake Myron",
        "storeOpeningDate": "ISODate('2024-09-28T18:23:21.591Z')",
        "lastUpdated": "Timestamp({ t: 1730139801, i: 1 })",
        "storeFeatures": 239
    },
    {
        "_id": "44fdb9b9-df83-4492-8f71-b6ef648aa312",
        "name": "Fourth Coffee | Storage Solution Gallery - Port Camilla",
        "location": {
            "lat": 78.3889,
            "lon": 0.6784
        },
        "staff": {
            "employeeCount": {
                "fullTime": 17,
                "partTime": 15
            }
        },
        "sales": {
            "salesByCategory": [
                {
                    "categoryName": "Storage Boxes",
                    "totalSales": 2236
                }
            ],
            "revenue": 2236
        },
        "promotionEvents": [
            {
                "eventName": "Major Discount Mania",
                "promotionalDates": {
                    "startDate": {
                        "Year": 2024,
                        "Month": 6,
                        "Day": 23
                    },
                    "endDate": {
                        "Year": 2024,
                        "Month": 7,
                        "Day": 3
                    }
                },
                "discounts": [
                    {
                        "categoryName": "Bathroom Storage",
                        "discountPercentage": 19
                    },
                    {
                        "categoryName": "Kitchen Storage",
                        "discountPercentage": 10
                    }
                ]
            },
            {
                "eventName": "Flash Deal Frenzy",
                "promotionalDates": {
                    "startDate": {
                        "Year": 2024,
                        "Month": 9,
                        "Day": 21
                    },
                    "endDate": {
                        "Year": 2024,
                        "Month": 9,
                        "Day": 30
                    }
                },
                "discounts": [
                    {
                        "categoryName": "Under-Bed Storage",
                        "discountPercentage": 20
                    },
                    {
                        "categoryName": "Closet Organizers",
                        "discountPercentage": 21
                    }
                ]
            }
        ],
        "company": "Fourth Coffee",
        "city": "Port Camilla",
        "storeOpeningDate": "ISODate('2024-09-23T06:02:53.844Z')",
        "lastUpdated": "Timestamp({ t: 1729663373, i: 1 })",
        "storeFeatures": 222
    }
]

Exemple 3 : Ignorer des documents dans un pipeline complexe

Pour ignorer le premier événement de promotion, puis projeter les événements restants pour un magasin spécifique :

db.stores.aggregate([
  { $match: { "_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4", } },
  { $unwind: "$promotionEvents" },
  { $skip: 1 },
  { $project: { "promotionEvents": 1, _id: 0 } }
])

Les deux premiers résultats retournés par cette requête sont les suivants :

[
    {
        "promotionEvents": {
            "eventName": "Steal of a Deal Days",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 9,
                    "Day": 21
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 9,
                    "Day": 29
                }
            },
            "discounts": [
                {
                    "categoryName": "Organic Wine",
                    "discountPercentage": 19
                },
                {
                    "categoryName": "White Wine",
                    "discountPercentage": 20
                },
                {
                    "categoryName": "Sparkling Wine",
                    "discountPercentage": 19
                },
                {
                    "categoryName": "Whiskey",
                    "discountPercentage": 17
                },
                {
                    "categoryName": "Vodka",
                    "discountPercentage": 23
                }
            ]
        }
    },
    {
        "promotionEvents": {
            "eventName": "Summer Sale",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 6,
                    "Day": 1
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 6,
                    "Day": 15
                }
            },
            "discounts": [
                {
                    "categoryName": "DJ Speakers",
                    "discountPercentage": 20
                }
            ]
        }
    }
]