Mongodb過濾器

Mongodb使用過濾器 $filter 根據(jù)指定條件選擇要返回的數(shù)組子集。返回僅包含與條件匹配的元素的數(shù)組。返回的元素按原始順序排列。
也就是說，這個是選擇你要的文檔，而不是排除。 如果該數(shù)組沒有符合條件 ，則為 空 []

$filter: 選擇數(shù)組的子集以返回僅包含與過濾條件匹配的元素的數(shù)組。

插入測試數(shù)據(jù)

sit_rs1:PRIMARY> db.user.insertMany([
...  { name: "user1", age: 10, letter: [{"x":"X1", "y":"Y1"}, {"x":"X2", "y":"Y2"}, {"x":"X3", "y":"Y3"}], number: [ { "n1":2, "n2":6 }, { "n1":3, "n2":3 }, { "n1":5, "n2":6 } ] },
...  { name: "user2", age: 20, letter: [{"V":"V1", "y":"Y1"}, {"V":"V2", "y":"Y2"}, {"V":"V3", "y":"Y3"}], number: [ { "n1":1, "n2":3 }, { "n1":4, "n2":5 }, { "n1":7, "n2":6 } ] },
...  { name: "user3", age: 30, letter: [{"V":"V1", "w":"W1"}, {"V":"V2", "w":"W2"}, {"V":"V3", "w":"W3"}], number: [ { "n1":1, "n2":8 }, { "n1":2, "n2":6 }, { "n1":2, "n2":6 } ] },
...  { name: "user4", age: 45, letter: [{"z":"Z1", "w":"W1"}, {"z":"Z2", "w":"W2"}, {"z":"Z3", "w":"W3"}], number: [ { "n1":9, "n2":8 }, { "n1":2, "n2":4 }, { "n1":3, "n2":6 } ] },
...  { name: "user5", age: 55, letter: [{"z":"Z1", "u":"U1"}, {"z":"Z2", "u":"U2"}, {"z":"Z3", "u":"U3"}], number: [ { "n1":7, "n2":8 }, { "n1":8, "n2":4 }, { "n1":4, "n2":6 } ] },
...  { name: "user6", age: 55, letter: [{"t":"T1", "u":"U1"}, {"t":"T2", "u":"U2"}, {"t":"T3", "u":"U3"}], number: [ { "n1":5, "n2":8 }, { "n1":8, "n2":5 }, { "n1":7, "n2":6 } ] },
... ])
{
        "acknowledged" : true,
        "insertedIds" : [
                ObjectId("64b661869be837dc8e997b74"),
                ObjectId("64b661869be837dc8e997b75"),
                ObjectId("64b661869be837dc8e997b76"),
                ObjectId("64b661869be837dc8e997b77"),
                ObjectId("64b661869be837dc8e997b78"),
                ObjectId("64b661869be837dc8e997b79")
        ]
}
sit_rs1:PRIMARY> db.user.find()
{ "_id" : ObjectId("64b661869be837dc8e997b74"), "name" : "user1", "age" : 10, "letter" : [ { "x" : "X1", "y" : "Y1" }, { "x" : "X2", "y" : "Y2" }, { "x" : "X3", "y" : "Y3" } ], "number" : [ { "n1" : 2, "n2" : 6 }, { "n1" : 3, "n2" : 3 }, { "n1" : 5, "n2" : 6 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b75"), "name" : "user2", "age" : 20, "letter" : [ { "V" : "V1", "y" : "Y1" }, { "V" : "V2", "y" : "Y2" }, { "V" : "V3", "y" : "Y3" } ], "number" : [ { "n1" : 1, "n2" : 3 }, { "n1" : 4, "n2" : 5 }, { "n1" : 7, "n2" : 6 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b76"), "name" : "user3", "age" : 30, "letter" : [ { "V" : "V1", "w" : "W1" }, { "V" : "V2", "w" : "W2" }, { "V" : "V3", "w" : "W3" } ], "number" : [ { "n1" : 1, "n2" : 8 }, { "n1" : 2, "n2" : 6 }, { "n1" : 2, "n2" : 6 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b77"), "name" : "user4", "age" : 45, "letter" : [ { "z" : "Z1", "w" : "W1" }, { "z" : "Z2", "w" : "W2" }, { "z" : "Z3", "w" : "W3" } ], "number" : [ { "n1" : 9, "n2" : 8 }, { "n1" : 2, "n2" : 4 }, { "n1" : 3, "n2" : 6 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b78"), "name" : "user5", "age" : 55, "letter" : [ { "z" : "Z1", "u" : "U1" }, { "z" : "Z2", "u" : "U2" }, { "z" : "Z3", "u" : "U3" } ], "number" : [ { "n1" : 7, "n2" : 8 }, { "n1" : 8, "n2" : 4 }, { "n1" : 4, "n2" : 6 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b79"), "name" : "user6", "age" : 55, "letter" : [ { "t" : "T1", "u" : "U1" }, { "t" : "T2", "u" : "U2" }, { "t" : "T3", "u" : "U3" } ], "number" : [ { "n1" : 5, "n2" : 8 }, { "n1" : 8, "n2" : 5 }, { "n1" : 7, "n2" : 6 } ] }

$filter 具有以下語法：

{ $filter: { input: <array>, as: <string>, cond: <expression> } }

• input: 解析為數(shù)組的表達(dá)式。
• as: 可選的。代表數(shù)組中每個單獨元素的變量名稱input。如果未指定名稱，則變量名稱默認(rèn)為this。
• cond: 解析為布爾值的表達(dá)式，用于確定是否應(yīng)將某個元素包含在輸出數(shù)組中。表達(dá)式使用as中指定的變量名分別引用輸入數(shù)組的每個元素。

# 以下示例選擇 number 數(shù)組 n1 字段 僅包含 “大于5” 的文檔：

sit_rs1:PRIMARY> db.user.aggregate([
...    {
...       $project: {
...          number: {
...             $filter: {
...                input: "$number",
...                as: "number",
...                cond: { $gt: [ "$$number.n1", 5 ] }
...             }
...          }
...       }
...    }
... ])
{ "_id" : ObjectId("64b661869be837dc8e997b74"), "number" : [ ] }
{ "_id" : ObjectId("64b661869be837dc8e997b75"), "number" : [ { "n1" : 7, "n2" : 6 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b76"), "number" : [ ] }
{ "_id" : ObjectId("64b661869be837dc8e997b77"), "number" : [ { "n1" : 9, "n2" : 8 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b78"), "number" : [ { "n1" : 7, "n2" : 8 }, { "n1" : 8, "n2" : 4 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b79"), "number" : [ { "n1" : 8, "n2" : 5 }, { "n1" : 7, "n2" : 6 } ] }

as: 是可選的。如果未指定名稱，則變量名稱默認(rèn)為this。下面使用 this 代替。

sit_rs1:PRIMARY> db.user.aggregate([
...    {
...       $project: {
...          number: {
...             $filter: {
...                input: "$number",
...                cond: { $gt: [ "$$this.n1", 5 ] }
...             }
...          }
...       }
...    }
... ])
{ "_id" : ObjectId("64b661869be837dc8e997b74"), "number" : [ ] }
{ "_id" : ObjectId("64b661869be837dc8e997b75"), "number" : [ { "n1" : 7, "n2" : 6 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b76"), "number" : [ ] }
{ "_id" : ObjectId("64b661869be837dc8e997b77"), "number" : [ { "n1" : 9, "n2" : 8 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b78"), "number" : [ { "n1" : 7, "n2" : 8 }, { "n1" : 8, "n2" : 4 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b79"), "number" : [ { "n1" : 8, "n2" : 5 }, { "n1" : 7, "n2" : 6 } ] }

聚合管道更新

從 MongoDB 4.2 開始，您可以使用聚合管道進(jìn)行更新：使用聚合管道可以實現(xiàn)更具表現(xiàn)力的更新語句，例如基于當(dāng)前字段值表達(dá)條件更新或使用另一個字段的值更新一個字段。

以下示例，使用 filter 選擇數(shù)組的子集, 再更新原來的數(shù)組。文章來源地址http://www.zghlxwxcb.cn/news/detail-586140.html

# 以下示例選擇 number 數(shù)組 n1 字段 僅包含 “大于5” 的文檔：并更新替換原來的數(shù)組 
sit_rs1:PRIMARY> db.user.updateMany(
...   { "number": { $exists: true } }, 
...   [{ 
...       $set: { 
...           "number": { 
...               $filter: { 
...   			      input: "$number", 
...   			      as: "number", 
...   			      cond: { $gt: [ "$$number.n1", 5 ] }
...   			  } 
...   		   } 
...    	  } 
...   }] 
... )
{ "acknowledged" : true, "matchedCount" : 6, "modifiedCount" : 6 }

sit_rs1:PRIMARY> db.user.find()
{ "_id" : ObjectId("64b661869be837dc8e997b74"), "name" : "user1", "age" : 10, "letter" : [ { "x" : "X1", "y" : "Y1" }, { "x" : "X2", "y" : "Y2" }, { "x" : "X3", "y" : "Y3" } ], "number" : [ ] }
{ "_id" : ObjectId("64b661869be837dc8e997b75"), "name" : "user2", "age" : 20, "letter" : [ { "V" : "V1", "y" : "Y1" }, { "V" : "V2", "y" : "Y2" }, { "V" : "V3", "y" : "Y3" } ], "number" : [ { "n1" : 7, "n2" : 6 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b76"), "name" : "user3", "age" : 30, "letter" : [ { "V" : "V1", "w" : "W1" }, { "V" : "V2", "w" : "W2" }, { "V" : "V3", "w" : "W3" } ], "number" : [ ] }
{ "_id" : ObjectId("64b661869be837dc8e997b77"), "name" : "user4", "age" : 45, "letter" : [ { "z" : "Z1", "w" : "W1" }, { "z" : "Z2", "w" : "W2" }, { "z" : "Z3", "w" : "W3" } ], "number" : [ { "n1" : 9, "n2" : 8 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b78"), "name" : "user5", "age" : 55, "letter" : [ { "z" : "Z1", "u" : "U1" }, { "z" : "Z2", "u" : "U2" }, { "z" : "Z3", "u" : "U3" } ], "number" : [ { "n1" : 7, "n2" : 8 }, { "n1" : 8, "n2" : 4 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b79"), "name" : "user6", "age" : 55, "letter" : [ { "t" : "T1", "u" : "U1" }, { "t" : "T2", "u" : "U2" }, { "t" : "T3", "u" : "U3" } ], "number" : [ { "n1" : 8, "n2" : 5 }, { "n1" : 7, "n2" : 6 } ] }

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