mongodb - 项目匹配数组中的字段值

Question

我想更改文档结构，只显示 definition 数组中与文档中的 idLanguage 匹配的定义。我该怎么做？

具有 3 个元素的 definition 数组的文档示例(idLanguage 的三个不同 id):

{
    "_id" : ObjectId("59bc29897d7934a6a7577ee0"),
    "reference" : "FIIG=A23900 INC=62356",
    "idTerm" : "0161-1#TM-218801#1",
    "idLanguage" : "0161-1#LG-000002#1",
    "statusTerm" : 0,
    "idOrganisation" : "0161-1#OG-000194#1",
    "idConcept" : "0161-1#01-000001#1",
    "term" : "ZRYCHLOVAC ZçVERU, KE KULOMETU                     ",
    "definition" : [ 
        {
            "_id" : ObjectId("59bc0bd77d7934a6a7243f05"),
            "reference" : "FIIG=A23900 INC=62356",
            "idDefinition" : "0161-1#DF-000001#1",
            "idLanguage" : "0161-1#LG-000001#1",
            "statusDefinition" : 0,
            "idOrganisation" : "0161-1#OG-002462#1",
            "definition" : "A metallic claw shaped pivoting item, designed to accelerate the weapon's recovery from recoil by assisting in realigning the breech with the barrel.",
            "idConcept" : "0161-1#01-000001#1"
        }, 
        {
            "_id" : ObjectId("59bc29047d7934a6a7370782"),
            "reference" : "FIIG=A23900 INC=62356",
            "idDefinition" : "0161-1#DF-283090#1",
            "idLanguage" : "0161-1#LG-000002#1",
            "statusDefinition" : 0,
            "idOrganisation" : "0161-1#OG-000194#1",
            "definition" : "Kovov‡ otocn‡ p‡kov‡ polo_ka pro zrychlov‡n’ obnoven’ stavu zbrane pred zpetn_m r‡zem /v_strelem t’m, _e napom‡h‡ osov_mu ztoto_nen’ z‡vorn’ku /z‡veru s hlavn’.",
            "idConcept" : "0161-1#01-000001#1"
        }, 
        {
            "_id" : ObjectId("59bc290b7d7934a6a73ce124"),
            "reference" : "FIIG=A23900 INC=62356",
            "idDefinition" : "0161-1#DF-668740#1",
            "idLanguage" : "0161-1#LG-000005#1",
            "statusDefinition" : 0,
            "idOrganisation" : "0161-1#OG-000200#1",
            "definition" : "Metalowy element wahliwy w ksztalcie szpona, przeznaczony do przyspieszenia powrotu broni po odrzucie poprzez wspomaganie ponownego ustawienia w linii zamka i lufy.",
            "idConcept" : "0161-1#01-000001#1"
        }
    ]
}

Answer 1

您可以使用 $indexOfArray和 $arrayElemAt以匹配值。较早的问题表明您至少使用 MongoDB 3.4，所以这应该不是问题:

db.collection.aggregate([
  { "$addFields": {
    "definition": {
      "$arrayElemAt": [
        "$definition.definition",
        { "$indexOfArray": [
          "$definition.idLanguage",
          "$idLanguage"
        }}
      ]
    }
  }}
])

在idLanguage匹配的位置，通过"definition"(字段)从数组中提取。因此，您将用匹配这些属性的奇异值替换“数组”。