在mongo视图中添加数组时，如何过滤数组？

Question

下面是名为"hero_foods“的集合中的一个文档

{
    "_id": "Almond Butter",
    "title": "Almond Butter",
    "food_group": "protein",
    "recommendations_group": [
        "DT1",
        "DT2",
        "DT3",
        "DT4"
    ]
}

下面是名为"recommendation_items“的集合中的一个文档

{
  "_id": "DT1",
  "type": "DIET",
  "title": "pfc",
  "recommendation_items": {
  "title": "What you'll eat",
    "food_groups": [
     {
        "title" : "Quality Carbs",
        "category_id" : "carbs"
     },
     {
        "title" : "Protein",
        "category_id" : "protein"
     },
     {
        "title" : "Healthy Fats",
        "category_id" : "fats"
     }
    ]
  }
}

下面是我的Mongo View创建查询

database.createView("recommendation_items_view",recommendation_items,
    Arrays.asList(new Document("$match", 
        new Document("type", "DIET")), 
        new Document("$lookup", 
        new Document("from", "hero_foods")
            .append("localField", "_id")
            .append("foreignField", "recommendations_group")
            .append("as", "recommendation_items.hero_foods_list")), 
        new Document("$set", 
        new Document("recommendation_items.food_groups.hero_foods_list", "$recommendation_items.hero_foods_list")), 
        new Document("$project", 
        new Document("recommendation_items.hero_foods_list", 0L))));

这将在视图中创建一个文档，如下所示：

{
    "_id": "DT1",
    "type": "DIET",
    "title": "pfc",
    "recommendation_items": {
        "title": "What you'll eat",
        "more_options": {
            "title": "Looking for more options?",
            "description": "Tailor your taste by answering our food preferences questionnaire"
        },
        "food_groups": [
            {
                "title": "Quality Carbs",
                "description": "High-quality carbs have essential vitamins, minerals, and nutrients in a natural 'package' that limits fluctuations in blood sugar and insulin that contribute, at least in part, to chronic illness and overeating",
                "image": "image/quality-carbs-thumb_",
                "category_id": "carbs",
                "hero_foods_list": [
                    {
                        "_id": "Almond Butter",
                        "title": "Almond Butter",
                        "short_description": "Almond butter is a food paste made from grinding almonds into a nut butter.",
                        "image_thumb": "/images/diet-almond-butter-thumb_",
                        "image_banner": "/images/diet-almond-butter-banner_",
                        "long_description": "Almond butter is a food paste made from grinding almonds into a nut butter. Almond butter may be crunchy or smooth, and is generally stir or no-stir Almond butter may be either raw or roasted, but this describes the almonds themselves, prior to grinding.",
                        "food_group": "protein",
                        "recommendations_group": [
                            "DT1",
                            "DT2",
                            "DT3",
                            "DT4"
                        ],
                        "disliked_food_categories": [
                            "tree_nuts"
                        ],
                        "eating_patterns": [
                            "vegetarian",
                            "plant_based"
                        ],
                        "eating_practices": [
                            "kosher",
                            "halal"
                        ]
                    }
                ]
            },
            {
                "title": "Protein",
                "description": "any of a class of nitrogenous organic compounds which have large molecules composed of one or more long chains of amino acids and are an essential part of all living organisms, especially as structural components of body tissues such as muscle, hair, etc., and as enzymes and antibodies.",
                "image": "image/protein-thumb_",
                "category_id": "protein",
                "hero_foods_list": [
                    {
                        "_id": "Almond Butter",
                        "title": "Almond Butter",
                        "short_description": "Almond butter is a food paste made from grinding almonds into a nut butter.",
                        "image_thumb": "/images/diet-almond-butter-thumb_",
                        "image_banner": "/images/diet-almond-butter-banner_",
                        "long_description": "Almond butter is a food paste made from grinding almonds into a nut butter. Almond butter may be crunchy or smooth, and is generally stir or no-stir Almond butter may be either raw or roasted, but this describes the almonds themselves, prior to grinding.",
                        "food_group": "protein",
                        "recommendations_group": [
                            "DT1",
                            "DT2",
                            "DT3",
                            "DT4"
                        ],
                        "disliked_food_categories": [
                            "tree_nuts"
                        ],
                        "eating_patterns": [
                            "vegetarian",
                            "plant_based"
                        ],
                        "eating_practices": [
                            "kosher",
                            "halal"
                        ]
                    }
                ]
            },
            {
                "title": "Healthy Fats",
                "description": "Monounsaturated fats and polyunsaturated fats are known as the “good fats” because they are good for your heart, your cholesterol, and your overall health. These fats can help to: Lower the risk of heart disease and stroke.",
                "image": "image/healthy-fats-thumb_",
                "category_id": "fats",
                "hero_foods_list": [
                    {
                        "_id": "Almond Butter",
                        "title": "Almond Butter",
                        "short_description": "Almond butter is a food paste made from grinding almonds into a nut butter.",
                        "image_thumb": "/images/diet-almond-butter-thumb_",
                        "image_banner": "/images/diet-almond-butter-banner_",
                        "long_description": "Almond butter is a food paste made from grinding almonds into a nut butter. Almond butter may be crunchy or smooth, and is generally stir or no-stir Almond butter may be either raw or roasted, but this describes the almonds themselves, prior to grinding.",
                        "food_group": "protein",
                        "recommendations_group": [
                            "DT1",
                            "DT2",
                            "DT3",
                            "DT4"
                        ],
                        "disliked_food_categories": [
                            "tree_nuts"
                        ],
                        "eating_patterns": [
                            "vegetarian",
                            "plant_based"
                        ],
                        "eating_practices": [
                            "kosher",
                            "halal"
                        ]
                    }
                ]
            }
        ]
    }
}

我想在各自的recommendation_items.food_groups中添加recommendation_items.food_groups.hero_foods_list，条件如下：

即我只想要“蛋白质”的food_groups中的“食物组-蛋白质”的recommendation_items.food_groups.hero_foods_list中的数据，如下所示

**

**{
    "_id": "DT1",
    "type": "DIET",
    "title": "pfc",
    "recommendation_items": {
        "title": "What you'll eat",
        "more_options": {
            "title": "Looking for more options?",
            "description": "Tailor your taste by answering our food preferences questionnaire"
        },
        "food_groups": [
            {
                "title": "Quality Carbs",
                "description": "High-quality carbs have essential vitamins, minerals, and nutrients in a natural 'package' that limits fluctuations in blood sugar and insulin that contribute, at least in part, to chronic illness and overeating",
                "image": "image/quality-carbs-thumb_",
                "category_id": "carbs",
                "hero_foods_list": []
            },
            {
                "title": "Protein",
                "description": "any of a class of nitrogenous organic compounds which have large molecules composed of one or more long chains of amino acids and are an essential part of all living organisms, especially as structural components of body tissues such as muscle, hair, etc., and as enzymes and antibodies.",
                "image": "image/protein-thumb_",
                "category_id": "protein",
                "hero_foods_list": [
                    {
                        "_id": "Almond Butter",
                        "title": "Almond Butter",
                        "short_description": "Almond butter is a food paste made from grinding almonds into a nut butter.",
                        "image_thumb": "/images/diet-almond-butter-thumb_",
                        "image_banner": "/images/diet-almond-butter-banner_",
                        "long_description": "Almond butter is a food paste made from grinding almonds into a nut butter. Almond butter may be crunchy or smooth, and is generally stir or no-stir Almond butter may be either raw or roasted, but this describes the almonds themselves, prior to grinding.",
                        "food_group": "protein",
                        "recommendations_group": [
                            "DT1",
                            "DT2",
                            "DT3",
                            "DT4"
                        ],
                        "disliked_food_categories": [
                            "tree_nuts"
                        ],
                        "eating_patterns": [
                            "vegetarian",
                            "plant_based"
                        ],
                        "eating_practices": [
                            "kosher",
                            "halal"
                        ]
                    }
                ]
            },
            {
                "title": "Healthy Fats",
                "description": "Monounsaturated fats and polyunsaturated fats are known as the “good fats” because they are good for your heart, your cholesterol, and your overall health. These fats can help to: Lower the risk of heart disease and stroke.",
                "image": "image/healthy-fats-thumb_",
                "category_id": "fats",
                "hero_foods_list": []
            }
        ]
    }
}**

**

Answer 1

我认为一个解决方案是这样的：

db.recommendation_items.aggregate([
   { $match: { type: "DIET" } },
   {
      $lookup: {
         from: "hero_foods",
         localField: "_id",
         foreignField: "recommendations_group",
         as: "recommendation_items.hero_foods_list"
      }
   },
   {
      $set: {
         "recommendation_items.food_groups": {
            $map: {
               input: "$recommendation_items.food_groups",
               as: "foodGroup",
               in: {
                  $mergeObjects: [
                     "$$foodGroup",
                     {
                        hero_foods_list: {
                           $filter: {
                              input: "$recommendation_items.hero_foods_list",
                              as: "heroFood",
                              cond: { $eq: ["$$foodGroup.category_id", "$$heroFood.food_group"] }
                           }
                        }
                     }
                  ]
               }
            }
         }
      }
   }
])

请参阅Mongo playground