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• findAndModify

findAndModify

Definition

findAndModify

The findAndModify command modifies and returns a single document. By default, the returned document does not include the modifications made on the update. To return the document with the modifications made on the update, use the new option.

The command has the following syntax:

copy

{
  findAndModify: <collection-name>,
  query: <document>,
  sort: <document>,
  remove: <boolean>,
  update: <document or aggregation pipeline>,
  new: <boolean>,
  fields: <document>,
  upsert: <boolean>,
  bypassDocumentValidation: <boolean>,
  writeConcern: <document>,
  collation: <document>,
  arrayFilters: <array>,
  hint: <document|string>,
  comment: <any>
}

The findAndModify command takes the following fields:

Field	Type	Description
query	document	Optional. The selection criteria for the modification. The query field employs the same query selectors as used in the db.collection.find() method. Although the query may match multiple documents, findAndModify will only select one document to modify. If unspecified, defaults to an empty document. Starting in MongoDB 4.2 (and 4.0.12+, 3.6.14+, and 3.4.23+), the operation errors if the query argument is not a document.
sort	document	Optional. Determines which document the operation modifies if the query selects multiple documents. findAndModify modifies the first document in the sort order specified by this argument. Starting in MongoDB 4.2 (and 4.0.12+, 3.6.14+, and 3.4.23+), the operation errors if the sort argument is not a document.
remove	boolean	Must specify either the remove or the update field. Removes the document specified in the query field. Set this to true to remove the selected document . The default is false.
update	document or array	Must specify either the remove or the update field. Performs an update of the selected document. If passed a document with update operator expressions, findAndModify performs the specified modification. If passed a replacement document { <field1>: <value1>, ...}, the findAndModify performs a replacement. Starting in MongoDB 4.2, if passed an aggregation pipeline [ <stage1>, <stage2>, ... ], findAndModify modifies the document per the pipeline. The pipeline can consist of the following stages: $addFields and its alias $set $project and its alias $unset $replaceRoot and its alias $replaceWith.
new	boolean	Optional. When true, returns the modified document rather than the original. The findAndModify method ignores the new option for remove operations. The default is false.
fields	document	Optional. A subset of fields to return. The fields document specifies an inclusion of a field with 1, as in: fields: { <field1>: 1, <field2>: 1, ... }. See Projection. Starting in MongoDB 4.2 (and 4.0.12+, 3.6.14+, and 3.4.23+), the operation errors if the fields argument is not a document.
upsert	boolean	Optional. Used in conjuction with the update field. When true, findAndModify() either: Creates a new document if no documents match the query. For more details see upsert behavior. Updates a single document that matches the query. To avoid multiple upserts, ensure that the query fields are uniquely indexed. Defaults to false.
bypassDocumentValidation	boolean	Optional. Enables findAndModify to bypass document validation during the operation. This lets you update documents that do not meet the validation requirements. New in version 3.2.
writeConcern	document	Optional. A document expressing the write concern. Omit to use the default write concern. 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. New in version 3.2.
maxTimeMS	integer	Optional. Specifies a time limit in milliseconds for processing the operation.
findAndModify	string	The collection against which to run the command.
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: copy 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. You cannot specify multiple collations for an operation. For example, you cannot specify different collations per field, or if performing a find with a sort, you cannot use one collation for the find and another for the sort. New in version 3.4.
arrayFilters	array	Optional. An array of filter documents that determine which array elements to modify for an update operation on an array field. In the update document, use the $[<identifier>] filtered positional operator to define an identifier, which you then reference in the array filter documents. You cannot have an array filter document for an identifier if the identifier is not included in the update document. Note The <identifier> must begin with a lowercase letter and contain only alphanumeric characters. You can include the same identifier multiple times in the update document; however, for each distinct identifier ($[identifier]) in the update document, you must specify exactly one corresponding array filter document. That is, you cannot specify multiple array filter documents for the same identifier. For example, if the update statement includes the identifier x (possibly multiple times), you cannot specify the following for arrayFilters that includes 2 separate filter documents for x: // INVALID [ { "x.a": { $gt: 85 } }, { "x.b": { $gt: 80 } } ] However, you can specify compound conditions on the same identifier in a single filter document, such as in the following examples: copy // Example 1 [ { $or: [{"x.a": {$gt: 85}}, {"x.b": {$gt: 80}}] } ] // Example 2 [ { $and: [{"x.a": {$gt: 85}}, {"x.b": {$gt: 80}}] } ] // Example 3 [ { "x.a": { $gt: 85 }, "x.b": { $gt: 80 } } ] For examples, see Array Update Operations with arrayFilters. Note arrayFilters is not available for updates that use an aggregation pipeline. New in version 3.6.
hint	document or string	Optional. A document or string that specifies the index to use to support the query. The option can take an index specification document or the index name string. If you specify an index that does not exist, the operation errors. For an example, see Specify hint for findAndModify Operations. New in version 4.4.
comment	any	Optional. A user-provided comment to attach to this command. Once set, this comment appears alongside records of this command in the following locations: mongod log messages, in the attr.command.cursor.comment field. Database profiler output, in the command.comment field. currentOp output, in the command.comment field. A comment can be any valid BSON type (string, integer, object, array, etc). New in version 4.4.

Output

The findAndModify command returns a document with the following fields:

Field	Type	Description
value	document	Contains the command’s returned value. See value for details.
lastErrorObject	document	Contains information about updated documents. See lastErrorObject for details.
ok	number	Contains the command’s execution status. 1 on success, or 0 if an error occurred.

lastErrorObject

The lastErrorObject embedded document contains the following fields:

Field	Type	Description
updatedExisting	boolean	Contains true if an update operation modified an existing document.
upserted	document	Contains the ObjectId of the inserted document if an update operation with upsert: true resulted in a new document.

value

For remove operations, value contains the removed document if the query matches a document. If the query does not match a document to remove, value contains null.

For update operations, the value embedded document contains the following:

• If the new parameter is not set or is false:
  • the pre-modification document if the query matches a document;
  • otherwise, null.
• If new is true:
  • the modified document if the query returns a match;
  • the inserted document if upsert: true and no document matches the query;
  • otherwise, null.

Behavior

Upsert and Unique Index

When the findAndModify command includes the upsert: true option and the query field(s) is not uniquely indexed, the command could insert a document multiple times in certain circumstances.

Consider an example where no document with the name Andy exists and multiple clients issue the following command:

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db.runCommand(
   {
     findAndModify: "people",
     query: { name: "Andy" },
     sort: { rating: 1 },
     update: { $inc: { score: 1 } },
     upsert: true
   }
 )

If all the commands finish the query phase before any command starts the modify phase, and there is no unique index on the name field, the commands may each perform an upsert, creating multiple duplicate documents.

To prevent the creation of multiple duplicate documents, create a unique index on the name field. With the unique index in place, then the multiple findAndModify commands will exhibit one of the following behaviors:

• Exactly one findAndModify successfully inserts a new document.
• Zero or more findAndModify commands update the newly inserted document.
• Zero or more findAndModify commands fail when they attempt to insert a duplicate. If the command fails due to a unique index constraint violation, you can retry the command. Absent a delete of the document, the retry should not fail.

Sharded Collections

To use findAndModify on a sharded collection, the query filter must include an equality condition on the shard key.

Starting in version 4.4, documents in a sharded collection can be missing the shard key fields. To target a document that is missing the shard key, you can use the null equality match in conjunction with another filter condition (such as on the _id field). For example:

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{ _id: <value>, <shardkeyfield>: null } // _id of the document missing shard key

Shard Key Modification

Starting in MongoDB 4.2, you can update a document’s shard key value unless the shard key field is the immutable _id field. Before MongoDB 4.2, a document’s shard key field value is immutable.

Warning

Starting in version 4.4, documents in sharded collections can be missing the shard key fields. Take precaution to avoid accidentally removing the shard key when changing a document’s shard key value.

To modify the existing shard key value with findAndModify:

• You must run on a mongos. Do not issue the operation directly on the shard.
• You must run either in a transaction or as a retryable write.
• You must include an equality filter on the full shard key.

Missing Shard Key

Starting in version 4.4, documents in a sharded collection can be missing the shard key fields. To use findAndModify to set the document’s missing shard key:

• You must run on a mongos. Do not issue the operation directly on the shard.
• You must run either in a transaction or as a retryable write if the new shard key value is not null.
• You must include an equality filter on the full shard key.

Tip

Since a missing key value is returned as part of a null equality match, to avoid updating a null-valued key, include additional query conditions (such as on the _id field) as appropriate.

See also:

• Missing Shard Key

Document Validation

The findAndModify command adds support for the bypassDocumentValidation option, which lets you bypass document validation when inserting or updating documents in a collection with validation rules.

Comparisons with the update Method

When updating a document, findAndModify and the update() method operate differently:

• By default, both operations modify a single document. However, the update() method with its multi option can modify more than one document.

• If multiple documents match the update criteria, for findAndModify, you can specify a sort to provide some measure of control on which document to update.

  With the default behavior of the update() method, you cannot specify which single document to update when multiple documents match.

• By default, findAndModify returns an object that contains the pre-modified version of the document, as well as the status of the operation. To obtain the updated document, use the new option.

  The update() method returns a WriteResult object that contains the status of the operation. To return the updated document, use the find() method. However, other updates may have modified the document between your update and the document retrieval. Also, if the update modified only a single document but multiple documents matched, you will need to use additional logic to identify the updated document.

When modifying a single document, both findAndModify and the update() method atomically update the document. See Atomicity and Transactions for more details about interactions and order of operations of these methods.

Transactions

findAndModify can be used inside multi-document transactions.

Important

In most cases, multi-document transaction incurs a greater performance cost over single document writes, and the availability of multi-document transactions should not be a replacement for effective schema design. For many scenarios, the denormalized data model (embedded documents and arrays) will continue to be optimal for your data and use cases. That is, for many scenarios, modeling your data appropriately will minimize the need for multi-document transactions.

For additional transactions usage considerations (such as runtime limit and oplog size limit), see also Production Considerations.

Upsert within Transactions

Starting in MongoDB 4.4 with feature compatibility version (fcv) "4.4", you can create collections and indexes inside a multi-document transaction if the transaction is not a cross-shard write transaction.

As such, for the feature compatibility version (fcv) is "4.4" or greater, findAndModify with upsert: true can be run against an existing collection or a non-existing collection. If run against a non-existing collection, the operation creates the collection.

If the feature compatibility version (fcv) is "4.2" or less, the operation must be against an existing collection.

See also

Create Collections and Indexes In a Transaction

Write Concerns and Transactions

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.

Examples

Update and Return

The following command updates an existing document in the people collection where the document matches the query criteria:

copy

db.runCommand(
   {
     findAndModify: "people",
     query: { name: "Tom", state: "active", rating: { $gt: 10 } },
     sort: { rating: 1 },
     update: { $inc: { score: 1 } }
   }
)

This command performs the following actions:

1. The query finds a document in the people collection where the name field has the value Tom, the state field has the value active and the rating field has a value greater than 10.

2. The sort orders the results of the query in ascending order. If multiple documents meet the query condition, the command will select for modification the first document as ordered by this sort.

3. The update increments the value of the score field by 1.

4. The command returns a document with the following fields:

   • The lastErrorObject field that contains the details of the command, including the field updatedExisting which is true, and

   • The value field that contains the original (i.e. pre-modification) document selected for this update:

     copy

     {
       "lastErrorObject" : {
          "connectionId" : 1,
          "updatedExisting" : true,
          "n" : 1,
          "syncMillis" : 0,
          "writtenTo" : null,
          "err" : null,
          "ok" : 1
       },
       value" : {
         "_id" : ObjectId("54f62d2885e4be1f982b9c9c"),
         "name" : "Tom",
         "state" : "active",
         "rating" : 100,
         "score" : 5
       },
       "ok" : 1
     }
     

To return the modified document in the value field, add the new:true option to the command.

If no document match the query condition, the command returns a document that contains null in the value field:

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{ "value" : null, "ok" : 1 }

The mongo shell and many drivers provide a findAndModify() helper method. Using the shell helper, this previous operation can take the following form:

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db.people.findAndModify( {
   query: { name: "Tom", state: "active", rating: { $gt: 10 } },
   sort: { rating: 1 },
   update: { $inc: { score: 1 } }
} );

However, the findAndModify() shell helper method returns only the unmodified document, or if new is true, the modified document.

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{
   "_id" : ObjectId("54f62d2885e4be1f982b9c9c"),
   "name" : "Tom",
   "state" : "active",
   "rating" : 100,
   "score" : 5
}

upsert: true

The following findAndModify command includes the upsert: true option for the update operation to either update a matching document or, if no matching document exists, create a new document:

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db.runCommand(
               {
                 findAndModify: "people",
                 query: { name: "Gus", state: "active", rating: 100 },
                 sort: { rating: 1 },
                 update: { $inc: { score: 1 } },
                 upsert: true
               }
             )

If the command finds a matching document, the command performs an update.

If the command does not find a matching document, the update with upsert: true operation results in an insertion and returns a document with the following fields:

• The lastErrorObject field that contains the details of the command, including the field upserted that contains the _id value of the newly inserted document, and
• The value field containing null.

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{
  "value" : null,
  "lastErrorObject" : {
     "updatedExisting" : false,
     "n" : 1,
     "upserted" : ObjectId("54f62c8bc85d4472eadea26f")
  },
  "ok" : 1
}

Return New Document

The following findAndModify command includes both upsert: true option and the new:true option. The command either updates a matching document and returns the updated document or, if no matching document exists, inserts a document and returns the newly inserted document in the value field.

In the following example, no document in the people collection matches the query condition:

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db.runCommand(
   {
     findAndModify: "people",
     query: { name: "Pascal", state: "active", rating: 25 },
     sort: { rating: 1 },
     update: { $inc: { score: 1 } },
     upsert: true,
     new: true
   }
)

The command returns the newly inserted document in the value field:

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{
  "lastErrorObject" : {
     "connectionId" : 1,
     "updatedExisting" : false,
     "upserted" : ObjectId("54f62bbfc85d4472eadea26d"),
     "n" : 1,
     "syncMillis" : 0,
     "writtenTo" : null,
     "err" : null,
     "ok" : 1
  },
  "value" : {
     "_id" : ObjectId("54f62bbfc85d4472eadea26d"),
     "name" : "Pascal",
     "rating" : 25,
     "state" : "active",
     "score" : 1
  },
  "ok" : 1
}

Sort and Remove

By including a sort specification on the rating field, the following example removes from the people collection a single document with the state value of active and the lowest rating among the matching documents:

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db.runCommand(
   {
     findAndModify: "people",
     query: { state: "active" },
     sort: { rating: 1 },
     remove: true
   }
)

The command returns the deleted document:

copy

{
  "lastErrorObject" : {
     "connectionId" : 1,
     "n" : 1,
     "syncMillis" : 0,
     "writtenTo" : null,
     "err" : null,
     "ok" : 1
  },
  "value" : {
     "_id" : ObjectId("54f62a6785e4be1f982b9c9b"),
     "name" : "XYZ123",
     "score" : 1,
     "state" : "active",
     "rating" : 3
  },
  "ok" : 1
}

Specify Collation

New in version 3.4.

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:

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{ _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:

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db.runCommand(
   {
     findAndModify: "myColl",
     query: { category: "cafe", status: "a" },
     sort: { category: 1 },
     update: { $set: { status: "Updated" } },
     collation: { locale: "fr", strength: 1 }
   }
)

The operation returns the following document:

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{
   "lastErrorObject" : {
      "updatedExisting" : true,
      "n" : 1
   },
   "value" : {
      "_id" : 1,
      "category" : "café",
      "status" : "A"
   },
   "ok" : 1
}

Array Update Operations with arrayFilters

Note

arrayFilters is not available for updates that use an aggregation pipeline.

New in version 3.6.

Starting in MongoDB 3.6, when updating an array field, you can specify arrayFilters that determine which array elements to update.

Update Elements Match arrayFilters Criteria

Note

arrayFilters is not available for updates that use an aggregation pipeline.

Create a collection students with the following documents:

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db.students.insert([
   { "_id" : 1, "grades" : [ 95, 92, 90 ] },
   { "_id" : 2, "grades" : [ 98, 100, 102 ] },
   { "_id" : 3, "grades" : [ 95, 110, 100 ] }
])

To modify all elements that are greater than or equal to 100 in the grades array, use the positional $[<identifier>] operator with the arrayFilters option:

copy

db.runCommand(
   {
     findAndModify: "students",
     query: { grades: { $gte: 100 } },
     update:  { $set: { "grades.$[element]" : 100 } },
     arrayFilters: [ { "element": { $gte: 100 } } ]
   }
)

The operation updates the grades field for a single document, and after the operation, the collection has the following documents:

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{ "_id" : 1, "grades" : [ 95, 92, 90 ] }
{ "_id" : 2, "grades" : [ 98, 100, 100 ] }
{ "_id" : 3, "grades" : [ 95, 110, 100 ] }

Update Specific Elements of an Array of Documents

Note

arrayFilters is not available for updates that use an aggregation pipeline.

Create a collection students2 with the following documents:

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db.students2.insert([
   {
      "_id" : 1,
      "grades" : [
         { "grade" : 80, "mean" : 75, "std" : 6 },
         { "grade" : 85, "mean" : 90, "std" : 4 },
         { "grade" : 85, "mean" : 85, "std" : 6 }
      ]
   },
   {
      "_id" : 2,
      "grades" : [
         { "grade" : 90, "mean" : 75, "std" : 6 },
         { "grade" : 87, "mean" : 90, "std" : 3 },
         { "grade" : 85, "mean" : 85, "std" : 4 }
      ]
   }
])

The following operation finds a document where the _id field equals 1 and uses the filtered positional operator $[<identifier>] with the arrayFilters to modify the mean for all elements in the grades array where the grade is greater than or equal to 85.

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db.runCommand(
   {
     findAndModify: "students2",
     query: { _id : 1 },
     update: { $set: { "grades.$[elem].mean" : 100 } },
     arrayFilters: [ { "elem.grade": { $gte: 85 } } ]
   }
)

The operation updates the grades field for a single document, and after the operation, the collection has the following documents:

copy

{
   "_id" : 1,
   "grades" : [
      { "grade" : 80, "mean" : 75, "std" : 6 },
      { "grade" : 85, "mean" : 100, "std" : 4 },
      { "grade" : 85, "mean" : 100, "std" : 6 }
    ]
}
{
   "_id" : 2,
   "grades" : [
      { "grade" : 90, "mean" : 75, "std" : 6 },
      { "grade" : 87, "mean" : 90, "std" : 3 },
      { "grade" : 85, "mean" : 85, "std" : 4 }
   ]
}

Use an Aggregation Pipeline for Updates

Starting in MongoDB 4.2, findAndModify can accept an aggregation pipeline for the update. The pipeline can consist of the following stages:

• $addFields and its alias $set
• $project and its alias $unset
• $replaceRoot and its alias $replaceWith.

Using the aggregation pipeline allows for a more expressive update statement, such as expressing conditional updates based on current field values or updating one field using the value of another field(s).

For example, create a collection students2 with the following documents:

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db.students2.insert([
   {
      "_id" : 1,
      "grades" : [
         { "grade" : 80, "mean" : 75, "std" : 6 },
         { "grade" : 85, "mean" : 90, "std" : 4 },
         { "grade" : 85, "mean" : 85, "std" : 6 }
      ]
   },
   {
      "_id" : 2,
      "grades" : [
         { "grade" : 90, "mean" : 75, "std" : 6 },
         { "grade" : 87, "mean" : 90, "std" : 3 },
         { "grade" : 85, "mean" : 85, "std" : 4 }
      ]
   }
])

The following operation finds a document where the _id field equals 1 and uses an aggregation pipeline to calculate a new field total from the grades field:

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db.runCommand(
   {
     findAndModify: "students2",
     query: {  "_id" : 1 },
     update: [ { $set: { "total" : { $sum: "$grades.grade" } } } ],
     new: true
   }
)

Note

The $set used in the pipeline refers to the aggregation stage $set and not the update operator $set.

After the operation, the collection has the following documents:

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{
  "_id" : 1,
  "grades" : [ { "grade" : 80, "mean" : 75, "std" : 6 }, { "grade" : 85, "mean" : 90, "std" : 4 }, { "grade" : 85, "mean" :85, "std" : 6 } ],
  "total" : 250
}
{
   "_id" : 2,
   "grades" : [ { "grade" : 90, "mean" : 75, "std" : 6 }, { "grade" : 87, "mean" : 90, "std" : 3 }, { "grade" : 85, "mean" : 85,"std" : 4 } ]
}

Specify hint for findAndModify Operations

New in version 4.4.

From the mongo shell, create a members collection with the following documents:

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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:

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

The following operation explicitly hints to use the index { status: 1 }:

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db.runCommand({
   findAndModify: "members",
   query: { "points": { $lte: 20 }, "status": "P" },
   remove: true,
   hint: { status: 1 }
})

Note

If you specify an index that does not exist, the operation errors.

To see the index used, run explain on the operation:

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db.runCommand(
   {
     explain: {
       findAndModify: "members",
       query: { "points": { $lte: 20 }, "status": "P" },
       remove: true,
       hint: { status: 1 }
     },
     verbosity: "queryPlanner"
   }
)

See also

Linearizable Reads via findAndModify

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