delete (database command)（数据库命令）

Sharded Collections分片化集合

To use delete operations for a sharded collection that specify the limit: 1 option:要对指定limit:1选项的分片集合使用delete操作，请执行以下操作：

• If you only target one shard, you can use a partial shard key in the query specification or,如果你只针对一个分片，你可以在查询规范中使用部分分片键，或者，
• You can provide the shard key or the _id field in the query specification.您可以在查询规范中提供分片键或_id字段。

Limits限制

The total size of all the queries (i.e. the q field values) in the deletes array must be less than or equal to the maximum BSON document size.deletes数组中所有查询（即q字段值）的总大小必须小于或等于BSON文档的最大大小。

The total number of delete documents in the deletes array must be less than or equal to the maximum bulk size.deletes数组中删除文档的总数必须小于或等于最大批量大小。

Transactions事务

delete can be used inside distributed transactions.delete可以在分布式事务中使用。

Do not explicitly set the write concern for the operation if run in a transaction. To use write concern with transactions, see Transactions and Write Concern.如果在事务中运行，则不要显式设置操作的写入关注。要对事务使用写关注，请参阅事务和写关注。

Limit the Number of Documents Deleted限制删除的文档数量

The following example deletes from the orders collection one document that has the status equal to D by specifying the limit of 1:以下示例通过指定limit: 1从orders集合中删除一个status为D的文档：

db.runCommand(
   {
      delete: "orders",
      deletes: [ { q: { status: "D" }, limit: 1 } ]
   }
)

The returned document shows that the command deleted 1 document. 返回的文档显示该命令删除了1个文档。See Output输出 for details.详见输出。

{ "ok" : 1, "n" : 1 }

Delete All Documents That Match a Condition删除符合条件的所有文档

The following example deletes from the orders collection all documents that have the status equal to D by specifying the limit of 0:以下示例通过指定limit: 0从orders集合中删除status为D的所有文档：

db.runCommand(
   {
      delete: "orders",
      deletes: [ { q: { status: "D" }, limit: 0 } ],
      writeConcern: { w: "majority", wtimeout: 5000 }
   }
)

The returned document shows that the command found and deleted 13 documents. 返回的文档显示该命令找到并删除了13个文档。See Output输出 for details.详见输出。

{ "ok" : 1, "n" : 13 }

Delete All Documents from a Collection从集合中删除所有文档

Delete all documents in the orders collection by specifying an empty query condition and a limit of 0:通过指定空查询条件和limit:0删除orders集合中的所有文档：

db.runCommand(
   {
      delete: "orders",
      deletes: [ { q: { }, limit: 0 } ],
      writeConcern: { w: "majority", wtimeout: 5000 }
   }
)

The returned document shows that the command found and deleted 35 documents in total. See Output for details.返回的文档显示，该命令共找到并删除了35个文档。详见输出。

{ "ok" : 1, "n" : 35 }

Bulk Delete批量删除

The following example performs multiple delete operations on the orders collection:以下示例对orders集合执行多个删除操作：

db.runCommand(
   {
      delete: "orders",
      deletes: [
         { q: { status: "D" }, limit: 0 },
         { q: { cust_num: 99999, item: "abc123", status: "A" }, limit: 1 }
      ],
      ordered: false,
      writeConcern: { w: 1 }
   }
)

The returned document shows that the command found and deleted 21 documents in total for the two delete statements. 返回的文档显示，该命令在两个delete语句中总共找到并删除了21个文档。See Output输出 for details.详见输出。

{ "ok" : 1, "n" : 21 }

Specify Collation指定排序规则

Collation排序规则 allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks.允许用户为字符串比较指定特定于语言的规则，例如字母大小写和重音标记的规则。

A collection myColl has the following documents:myColl集合有以下文件：

{ _id: 1, category: "café", status: "A" }
{ _id: 2, category: "cafe", status: "a" }
{ _id: 3, category: "cafE", status: "a" }

The following operation includes the collation option:以下操作包括collation选项：

db.runCommand({
   delete: "myColl",
   deletes: [
     { q: { category: "cafe", status: "a" }, limit: 0, collation: { locale: "fr", strength: 1 } }
   ]
})

Specify hint for Delete Operations指定删除操作的hint（提示）

In mongosh, create a members collection with the following documents:在mongosh中，使用以下文档创建一个members集合：

db.members.insertMany([
   { "_id" : 1, "member" : "abc123", "status" : "P", "points" :  0,  "misc1" : null, "misc2" : null },
   { "_id" : 2, "member" : "xyz123", "status" : "A", "points" : 60,  "misc1" : "reminder: ping me at 100pts", "misc2" : "Some random comment" },
   { "_id" : 3, "member" : "lmn123", "status" : "P", "points" :  0,  "misc1" : null, "misc2" : null },
   { "_id" : 4, "member" : "pqr123", "status" : "D", "points" : 20,  "misc1" : "Deactivated", "misc2" : null },
   { "_id" : 5, "member" : "ijk123", "status" : "P", "points" :  0,  "misc1" : null, "misc2" : null },
   { "_id" : 6, "member" : "cde123", "status" : "A", "points" : 86,  "misc1" : "reminder: ping me at 100pts", "misc2" : "Some random comment" }
])

Create the following indexes on the collection:在集合上创建以下索引：

db.members.createIndex( { status: 1 } )
db.members.createIndex( { points: 1 } )

The following delete operation explicitly hints to use the index { status: 1 }:以下删除操作明确提示使用索引{ status: 1 }：

db.runCommand({
   delete: "members",
   deletes: [
     { q: { "points": { $lte: 20 }, "status": "P" }, limit: 0, hint: { status: 1 } }
   ]
})

To see the index used, run explain on the operation:要查看使用的索引，请在操作上运行explain：

db.runCommand(
   {
     explain: {
       delete: "members",
       deletes: [
         { q: { "points": { $lte: 20 }, "status": "P" }, limit: 0, hint: { status: 1 } }
       ]
     },
     verbosity: "queryPlanner"
   }
)

Use Variables in let在let中使用变量

To define variables that you can access elsewhere in the command, use the let option.要定义可以在命令的其他地方访问的变量，请使用let选项。

Create a collection cakeFlavors:创建一个集合cakeFlavors（蛋糕口味）：

db.cakeFlavors.insertMany( [
   { _id: 1, flavor: "chocolate" },
   { _id: 2, flavor: "strawberry" },
   { _id: 3, flavor: "cherry" }
] )

The following example defines a targetFlavor variable in let and uses the variable to delete the strawberry cake flavor:以下示例在let中定义了targetFlavor变量，并使用该变量删除草莓蛋糕风味：

db.runCommand( {
   delete: db.cakeFlavors.getName(),
   deletes: [ {
      q: { $expr: { $eq: [ "$flavor", "$$targetFlavor" ] } },
      limit: 1
   } ],
   let : { targetFlavor: "strawberry" }
} )