delete¶

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Definition
Behavior
Examples
Output

Definition¶

delete¶

2.6 新版功能.

The delete command removes documents from a collection. A single delete command can contain multiple delete specifications. The command cannot operate on capped collections. The remove methods provided by the MongoDB drivers use this command internally.

The delete command has the following syntax:

{
   delete: <collection>,
   deletes: [
      { q : <query>, limit : <integer>, collation: <document> },
      { q : <query>, limit : <integer>, collation: <document> },
      { q : <query>, limit : <integer>, collation: <document> },
      ...
   ],
   ordered: <boolean>,
   writeConcern: { <write concern> }
}

The command takes the following fields:

Field	Type	Description
`delete`	string	The name of the target collection.
`deletes`	array	An array of one or more delete statements to perform in the named collection.
`ordered`	boolean	Optional. If `true`, then when a delete statement fails, return without performing the remaining delete statements. If `false`, then when a delete statement fails, continue with the remaining delete statements, if any. Defaults to `true`.
`writeConcern`	document	Optional. A document expressing the write concern of the `delete` command. Omit to use the default write concern.

Each element of the deletes array contains the following fields:

Field Type Description

q document The query that matches documents to delete.

limit integer The number of matching documents to delete. Specify either a 0 to delete all matching documents or 1 to delete a single document.

collation

document

Optional.

Specifies the collation to use for the operation.

Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks.

The collation option has the following syntax:

collation: {
   locale: <string>,
   caseLevel: <boolean>,
   caseFirst: <string>,
   strength: <int>,
   numericOrdering: <boolean>,
   alternate: <string>,
   maxVariable: <string>,
   backwards: <boolean>
}

When specifying collation, the locale field is mandatory; all other collation fields are optional. For descriptions of the fields, see Collation Document.

If the collation is unspecified but the collection has a default collation (see db.createCollection()), the operation uses the collation specified for the collection.

If no collation is specified for the collection or for the operations, MongoDB uses the simple binary comparison used in prior versions for string comparisons.

3.4 新版功能.

返回:	A document that contains the status of the operation. See Output for details.

Behavior¶

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.

The total number of delete documents in the deletes array must be less than or equal to the maximum bulk size.

Examples¶

Limit the Number of Documents Deleted¶

The following example deletes from the orders collection one document that has the status equal to D by specifying the limit of 1:

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

The returned document shows that the command deleted 1 document. See Output for details.

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

Delete All Documents That Match a Condition¶

The following example deletes from the orders collection all documents that have the status equal to D by specifying the limit of 0:

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. See Output for details.

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

Delete All Documents from a Collection¶

Delete all documents in the orders collection by specifying an empty query condition and a limit of 0:

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.

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

Bulk Delete¶

The following example performs multiple delete operations on the orders collection:

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. See Output for details.

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

Specify Collation¶

3.4 新版功能.

Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks.

A collection myColl has the following documents:

{ _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:

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

Output¶

The returned document contains a subset of the following fields:

delete.ok¶: The status of the command.

delete.n¶: The number of documents deleted.

delete.writeErrors¶

An array of documents that contains information regarding any error encountered during the delete operation. The writeErrors array contains an error document for each delete statement that errors.

Each error document contains the following information:

delete.writeErrors.index¶: An integer that identifies the delete statement in the deletes array, which uses a zero-based index.

delete.writeErrors.code¶: An integer value identifying the error.

delete.writeErrors.errmsg¶: A description of the error.

delete.writeConcernError¶

Document that describe error related to write concern and contains the field:

delete.writeConcernError.code¶: An integer value identifying the cause of the write concern error.

delete.writeConcernError.errmsg¶: A description of the cause of the write concern error.

The following is an example document returned for a successful delete command:

{ ok: 1, n: 1 }

The following is an example document returned for a delete command that encountered an error:

{
   "ok" : 1,
   "n" : 0,
   "writeErrors" : [
      {
         "index" : 0,
         "code" : 10101,
         "errmsg" : "can't remove from a capped collection: test.cappedLog"
      }
   ]
}

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