檢索MongoDB中集合的對象陣列中的特定元件

Question

我有以下文件：

{ 
    "_id" : 257655, 
    "name" : "Arrow", 
    "airsDayOfWeek" : "Wednesday", 
    "airsTime" : "8:00 PM", 
    "firstAired" : ISODate("2012-10-10T00:00:00.000+0000"), 
    "runtime" : 45, 
    "imdbId" : "tt2193021", 
    "seasons" : [ 
     { 
      "number" : 1, 
      "episodes" : [ 
       { 
        "_id" : 4599381, 
        "number" : 1, 
        "overview" : "Diggle and Felicity ...", 
       }, 
       { 
        "_id" : 4365918, 
        "number" : 2, 
        "overview" : "Oliver heads ...", 
       } 
      ] 
     }, 
     { 
      "number" : 2, 
      "episodes" : [ 
       { 
        "_id" : 4599398, 
        "number" : 1, 
        "overview" : "With crime in Starling Cit ...", 
       }, 
       { 
        "_id" : 4365989, 
        "number" : 2, 
        "overview" : "Oliver finds out the medicine ...", 
       } 
      ] 
     } 
    ] 
} 

以下查詢

db.shows.find({ 'seasons.episodes.number': 1, 'seasons.number': 1, _id: 257655 }) 

返回與seasons.episodes所有記錄文件

我也試過這個

db.shows.aggregate([ 
{$match: { '$and': [ {'seasons.number': 1}, { 'seasons.episodes.number': 1}, {_id: 257655}] }}, 
{$project: { 
    seasons: { 
     $filter: { 
     input: '$seasons', 
     as: 'seasons', 
     cond: {$eq: ['$$seasons.episodes.number', 1]} 
     } 
    } 
}} 
]) 

但我得到了一個錯誤：異常：無效運算符「$過濾器」

不過，我想只能用含有seasons.episodes.number = 1和seasons.number = 1

陣列獲取文檔

{ 
seasons" : [ 
     { 
      "number" : 1, 
      "episodes" : 
       { 
        "_id" : 4599381, 
        "number" : 1, 
        "overview" : "Diggle and Felicity ...", 
       } 
     } 
] 
} 

我該怎麼做？

Answer 1

如果限制的結果只與第一$匹配單個條目，你可以放鬆陣列並重組其對季節和情節，限制你的對手在系列和情節您感興趣的問題。

查詢

db.shows.aggregate([ 
{$match: { _id: 257655 }}, 
{$unwind: "$seasons" }, 
{$unwind: "$seasons.episodes" }, 
{$group: { _id: { series: "$seasons.number", ep: "$seasons.episodes.number" }, seasons: { $push: "$seasons" } } }, 
{$match: { "_id.series": 1, "_id.ep": 1} } 
]).pretty() 

結果

{ 
     "_id" : { 
       "series" : 1, 
       "ep" : 1 
     }, 
     "seasons" : [ 
       { 
         "number" : 1, 
         "episodes" : { 
           "_id" : 4599381, 
           "number" : 1, 
           "overview" : "Diggle and Felicity ..." 
         } 
       } 
     ] 
} 

Answer 2

它似乎只想提取節目的第一季（或每個節目）的第一集。如果是這種情況，在使用$ filter之後，您仍然需要$ unwind來標準化數組，因爲$ filter也會返回一個數組。

db.test.aggregate([ 
{$match: { '$and': [ {'seasons.number': 1}, { 'seasons.episodes.number': 1}, {_id: 257655}] }}, 
{$project: { 
    season1: { 
     $filter: { 
     input: '$seasons', 
     as: 'season', 
     cond: {$eq: ['$$season.number', 1]} 
     } 
    } 
}}, 
{$unwind : '$season1'}, 
{$project: { 
    episode1: { 
     $filter: { 
     input: '$season1.episodes', 
     as: 'episode', 
     cond: {$eq: ['$$episode.number', 1]} 
     } 
    } 
}} 
]).pretty() 

$開卷給你發作的第一個賽季的陣列，使用它可以再次使用$過濾器，只顯示（從數組）首發。