Mongodb过滤器filter选择要返回的数组子集操作方法
作者：Ethanchen's notes
Mongodb使用过滤器 $filter根据指定条件选择要返回的数组子集，这篇文章主要介绍了Mongodb对嵌套文档数组进行查询操作,需要的朋友可以参考下
Mongodb过滤器
Mongodb使用过滤器 $filter 根据指定条件选择要返回的数组子集。返回仅包含与条件匹配的元素的数组。返回的元素按原始顺序排列。也就是说，这个是选择你要的文档，而不是排除。 如果该数组没有符合条件 ，则为 空 []
$filter: 选择数组的子集以返回仅包含与过滤条件匹配的元素的数组。
插入测试数据
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 具有以下语法：
{ $filter: { input: <array>, as: <string>, cond: <expression> } }- input: 解析为数组的表达式。
- as: 可选的。代表数组中每个单独元素的变量名称input。如果未指定名称，则变量名称默认为this。
- cond: 解析为布尔值的表达式，用于确定是否应将某个元素包含在输出数组中。表达式使用as中指定的变量名分别引用输入数组的每个元素。
# 以下示例选择 number 数组 n1 字段 仅包含 “大于5” 的文档：
sit_rs1:PRIMARY> db.user.aggregate([
... {
... $project: {
... number: {
... $filter: {
... input: "$number",
... as: "number",
... cond: { $gt: [ "$$number.n1", 5 ] }
... }
... }
... }
... }
... ])
{ "_id" : ObjectId("64b661869be837dc8e997b74"), "number" : [ ] }
{ "_id" : ObjectId("64b661869be837dc8e997b75"), "number" : [ { "n1" : 7, "n2" : 6 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b76"), "number" : [ ] }
{ "_id" : ObjectId("64b661869be837dc8e997b77"), "number" : [ { "n1" : 9, "n2" : 8 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b78"), "number" : [ { "n1" : 7, "n2" : 8 }, { "n1" : 8, "n2" : 4 } ] }
{ "_id" : ObjectId("64b661869be837dc8e997b79"), "number" : [ { "n1" : 8, "n2" : 5 }, { "n1" : 7, "n2" : 6 } ] }as: 是可选的。如果未指定名称，则变量名称默认为this。下面使用 this 代替。
sit_rs1:PRIMARY> db.user.aggregate([
... {
... $project: {
... number: {
... $filter: {
... input: "$number",
... cond: { $gt: [ "$$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
从 MongoDB 4.2 开始，您可以使用聚合管道进行更新：使用聚合管道可以实现更具表现力的更新语句，例如基于当前字段值表达条件更新或使用另一个字段的值更新一个字段。
以下示例，使用 filter 选择数组的子集, 再更新原来的数组。
# 以下示例选择 number 数组 n1 字段 仅包含 “大于5” 的文档：并更新替换原来的数组
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 } ] }到此这篇关于Mongodb过滤器filter选择要返回的数组子集的文章就介绍到这了,更多相关Mongodb数组子集内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！