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$size

L’opérateur $size est utilisé pour interroger des documents où un champ de tableau a un nombre spécifié d’éléments. Cet opérateur est utile lorsque vous devez rechercher des documents en fonction de la taille d’un champ de tableau, comme la recherche de documents avec certains éléments d’une liste.

Syntaxe

db.collection.find({ <field>: { $size: <number> } })

Paramètres

Paramètre Descriptif
field Champ qui contient le tableau.
number Nombre d’éléments que le tableau doit avoir.

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": {
        "totalStaff": {
            "fullTime": 8,
            "partTime": 20
        }
    },
    "sales": {
        "totalSales": 75670,
        "salesByCategory": [
            {
                "categoryName": "Wine Accessories",
                "totalSales": 34440
            },
            {
                "categoryName": "Bitters",
                "totalSales": 39496
            },
            {
                "categoryName": "Rum",
                "totalSales": 1734
            }
        ]
    },
    "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
                }
            ]
        }
    ]
}

Exemple 1 : Recherche de documents avec un nombre spécifique d’éléments dans un tableau

Cette requête récupère des documents de la stores collection où le sales.salesByCategory tableau contient exactement sept éléments.

db.stores.find({
    "sales.salesByCategory": {
        $size: 7
    }
}, {
    _id: 1,
    name: 1,
    "sales.salesByCategory": 1
}).limit(2)

Cette requête retourne les résultats suivants :

[
    {
        "_id": "7ed4b356-1290-433e-bd96-bf95f817eaaa",
        "name": "Wide World Importers",
        "sales": {
            "salesByCategory": [
                {
                    "categoryName": "Ultrabooks",
                    "totalSales": 31304
                },
                {
                    "categoryName": "Laptop Accessories",
                    "totalSales": 10044
                },
                {
                    "categoryName": "Laptops",
                    "totalSales": 48851
                },
                {
                    "categoryName": "Refill Kits",
                    "totalSales": 9604
                },
                {
                    "categoryName": "Prepaid Phones",
                    "totalSales": 28600
                },
                {
                    "categoryName": "Android Phones",
                    "totalSales": 4580
                },
                {
                    "categoryName": "Photo Printers",
                    "totalSales": 35234
                }
            ]
        }
    },
    {
        "_id": "988d2dd1-2faa-4072-b420-b91b95cbfd60",
        "name": "Lakeshore Retail",
        "sales": {
            "salesByCategory": [
                {
                    "categoryName": "Towel Racks",
                    "totalSales": 13237
                },
                {
                    "categoryName": "Washcloths",
                    "totalSales": 44315
                },
                {
                    "categoryName": "Face Towels",
                    "totalSales": 42095
                },
                {
                    "categoryName": "Toothbrush Holders",
                    "totalSales": 47912
                },
                {
                    "categoryName": "Hybrid Mattresses",
                    "totalSales": 48660
                },
                {
                    "categoryName": "Napkins",
                    "totalSales": 31439
                },
                {
                    "categoryName": "Pillow Cases",
                    "totalSales": 38833
                }
            ]
        }
    }
]

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