find

Command Fields

The command accepts the following fields:

A batchSize of 0 means that the cursor is established, but no documents are returned in the first batch.

Unlike the previous wire protocol version, a batchSize of 1 for the find command does not close the cursor.

• • singleBatch

  • boolean

  • Optional. Determines whether to close the cursor after the first batch. Defaults to false.

• • 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).

    Any comment set on a find command is inherited by any subsequent getMore commands run on the find cursor.

• • maxTimeMS

  • non-negative integer

  • Optional.

    Specifies a time limit in milliseconds. If you do not specify a value for maxTimeMS, operations will not time out. A value of 0 explicitly specifies the default unbounded behavior.

    MongoDB terminates operations that exceed their allotted time limit using the same mechanism as db.killOp(). MongoDB only terminates an operation at one of its designated interrupt points.

    When specifying linearizable read concern, always use maxTimeMS in case a majority of data bearing members are unavailable. maxTimeMS ensures that the operation does not block indefinitely and instead returns an error if the read concern cannot be fulfilled.

• • readConcern

  • document

  • Optional. Specifies the read concern.

    The readConcern option has the following syntax: readConcern: { level: <value> }

    Possible read concern levels are:

    • "local". This is the default read concern level for read operations against the primary and secondaries.

    • "available". Available for read operations against the primary and secondaries. "available" behaves the same as "local" against the primary and non-sharded secondaries. The query returns the instance's most recent data.

    • "majority". Available for replica sets that use WiredTiger storage engine.

    • "linearizable". Available for read operations on the primary only.

    For more formation on the read concern levels, see Read Concern Levels.

    The getMore command uses the readConcern level specified in the originating find command.

• • max

  • document

  • Optional. The exclusive upper bound for a specific index. See cursor.max() for details.

    To use the max field, the command must also use hint unless the specified filter is an equality condition on the _id field { _id: <value> }.

• • min

  • document

  • Optional. The inclusive lower bound for a specific index. See cursor.min() for details.

    To use the min field, the command must also use hint unless the specified filter is an equality condition on the _id field { _id: <value> }.

• • returnKey

  • boolean

  • Optional. If true, returns only the index keys in the resulting documents. Default value is false. If returnKey is true and the find command does not use an index, the returned documents will be empty.

• • showRecordId

  • boolean

  • Optional. Determines whether to return the record identifier for each document. If true, adds a field $recordId to the returned documents.

• • tailable

  • boolean

  • Optional. Returns a tailable cursor for a capped collections.

• • awaitData

  • boolean

  • Optional. Use in conjunction with the tailable option to block a getMore command on the cursor temporarily at the end of data rather than returning no data. After a timeout period, find returns as normal.

• • noCursorTimeout

  • boolean

  • Optional. Prevents the server from timing out non-session idle cursors after an inactivity period of 30 minutes. Ignored for cursors that are part of a session. For more information, refer to Session Idle Timeout.

• • allowPartialResults

  • boolean

  • Optional. For queries against a sharded collection, allows the command (or subsequent getMore commands) to return partial results, rather than an error, if one or more queried shards are unavailable.

    If find (or subsequent getMore commands) returns partial results because the queried shard(s) aren't available, the find output includes a partialResultsReturned indicator field. If the queried shards are available for the initial find command, but one or more shards become unavailable for subsequent getMore commands, only the getMore commands that run while the shards aren't available include partialResultsReturned in their output.

• • 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.

    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.

• • allowDiskUse

  • boolean

  • Optional.

    Use this option to override allowDiskUseByDefault for a specific query. You can use this option to either:

    • Prohibit disk use on a system where disk use is allowed by default.

    • Allow disk use on a system where disk use is prohibited by default.

    Starting in MongoDB 6.0, if allowDiskUseByDefault is set to true and the server requires more than 100 megabytes of memory for a pipeline execution stage, MongoDB automatically writes temporary files to disk unless the query specifies { allowDiskUse: false }.

    For details, see allowDiskUseByDefault.

    allowDiskUse has no effect if MongoDB can satisfy the specified sort using an index, or if the blocking sort requires less than 100 megabytes of memory.

    For more complete documentation on allowDiskUse, see cursor.allowDiskUse().

    For more information on memory restrictions for large blocking sorts, see Sort and Index Use.

• • let

  • document

  • Optional.

    Specifies a document with a list of variables. This allows you to improve command readability by separating the variables from the query text.

    The document syntax is:

    {
      <variable_name_1>: <expression_1>,
      ...,
      <variable_name_n>: <expression_n>
    }

    The variable is set to the value returned by the expression, and cannot be changed afterwards.

    To access the value of a variable in the command, use the double dollar sign prefix ($$) together with your variable name in the form $$<variable_name>. For example: $$targetTotal.

    To use a variable to filter results, you must access the variable within the $expr operator.

    For a complete example using let and variables, see Use Variables in let.

    New in version 5.0.

Output

The command returns a document that contains the cursor information, including the cursor ID and the first batch of documents. For example, the following document is returned when run against a sharded collection:

{
   "cursor" : {
      "firstBatch" : [
         {
            "_id" : ObjectId("5e8e2ca217b5324fa9847435"),
            "zipcode" : "20001",
            "x" : 1
         },
         {
            "_id" : ObjectId("5e8e2ca517b5324fa9847436"),
            "zipcode" : "30001",
            "x" : 1
         }
      ],
      "partialResultsReturned" : true,
      "id" : NumberLong("668860441858272439"),
      "ns" : "test.contacts"
   },
   "ok" : 1,
   "operationTime" : Timestamp(1586380205, 1),
   "$clusterTime" : {
      "clusterTime" : Timestamp(1586380225, 2),
      "signature" : {
         "hash" : BinData(0,"aI/jWsUVUSkMw8id+A+AVVTQh9Y="),
         "keyId" : NumberLong("6813364731999420435")
      }
   }
}

In addition to the aforementioned find-specific fields, the db.runCommand() includes the following information for replica sets and sharded clusters:

• $clusterTime

• operationTime

See db.runCommand() Results for details.

$regex Find Queries No Longer Ignore Invalid Regex

Starting in MongoDB 5.1, invalid $regex options options are no longer ignored. This change makes $regex options more consistent with the use of $regex in the aggregate command and projection queries.

Sessions

For cursors created inside a session, you cannot call getMore outside the session.

Similarly, for cursors created outside of a session, you cannot call getMore inside a session.

Transactions

find can be used inside distributed transactions.

• For cursors created outside of a transaction, you cannot call getMore inside the transaction.

• For cursors created in a transaction, you cannot call getMore outside the transaction.

Client Disconnection

Starting in MongoDB 4.2, if the client that issued find disconnects before the operation completes, MongoDB marks find for termination using killOp.

Stable API

When using Stable API V1, the following find command fields are not supported:

• awaitData

• max

• min

• noCursorTimeout

• oplogReplay

• returnKey

• showRecordId

• tailable

Index Filters and Collations

Starting in MongoDB 6.0, an index filter uses the collation previously set using the planCacheSetFilter command.

Starting in MongoDB 8.0, use query settings instead of adding index filters. Index filters are deprecated starting in MongoDB 8.0.

Query settings have more functionality than index filters. Also, index filters aren't persistent and you cannot easily create index filters for all cluster nodes. To add query settings and explore examples, see setQuerySettings.

Find Cursor Behavior on Views

Starting in MongoDB 7.3, when you use a find command on a view with the singleBatch: true and batchSize: 1 options, a cursor is no longer returned. In previous versions of MongoDB these find queries would return a cursor even when you set the single batch option to true.

Query Settings

You can use query settings to set index hints, set operation rejection filters, and other fields. The settings apply to the query shape on the entire cluster. The cluster retains the settings after shutdown.

The query optimizer uses the query settings as an additional input during query planning, which affects the plan selected to run the query. You can also use query settings to block a query shape.

To add query settings and explore examples, see setQuerySettings.

You can add query settings for find, distinct, and aggregate commands.

Query settings have more functionality and are preferred over deprecated index filters.

To remove query settings, use removeQuerySettings. To obtain the query settings, use a $querySettings stage in an aggregation pipeline.

Specify a Sort and Limit

The following command runs the find command filtering on the rating field and the cuisine field. The command includes a projection to only return the following fields in the matching documents: _id, name, rating, and address fields.

The command sorts the documents in the result set by the name field and limits the result set to 5 documents.

db.runCommand(
   {
     find: "restaurants",
     filter: { rating: { $gte: 9 }, cuisine: "italian" },
     projection: { name: 1, rating: 1, address: 1 },
     sort: { name: 1 },
     limit: 5
   }
)

Override Default Read Concern

To override the default read concern level of "local", use the readConcern option.

The following operation on a replica set specifies a read concern of "majority" to read the most recent copy of the data confirmed as having been written to a majority of the nodes.

db.runCommand(
   {
     find: "restaurants",
     filter: { rating: { $lt: 5 } },
     readConcern: { level: "majority" }
   }
)

Regardless of the read concern level, the most recent data on a node may not reflect the most recent version of the data in the system.

The getMore command uses the readConcern level specified in the originating find command.

A readConcern can be specified for the mongosh method db.collection.find() using the cursor.readConcern() method:

db.restaurants.find( { rating: { $lt: 5 } } ).readConcern("majority")

For more information on available read concerns, see Read Concern.

Specify Collation

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

The following operation runs the find command with the collation specified:

db.runCommand(
   {
     find: "myColl",
     filter: { category: "cafe", status: "a" },
     sort: { category: 1 },
     collation: { locale: "fr", strength: 1 }
   }
)

mongosh provides the cursor.collation() to specify collation for a db.collection.find() operation.

Use Variables in let

To define variables that you can access elsewhere in the command, use the let option.

Create a collection cakeFlavors:

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 retrieve the chocolate cake flavor:

db.cakeFlavors.runCommand( {
   find: db.cakeFlavors.getName(),
   filter: { $expr: { $eq: [ "$flavor", "$$targetFlavor" ] } },
   let : { targetFlavor: "chocolate" }
} )