find

sort

Optional. The projection specification to determine which fields to include in the returned documents. See Projection and Projection Operators.

find() operations on views do not support the following projection operators:

• $

• $elemMatch

• $slice

• $meta

Optional. Index specification. Specify either the index name as a string or the index key pattern. If specified, then the query system will only consider plans using the hinted index.

With the following exception, hint is required if the command includes the min and/or max fields; hint is not required with min and/or max if the filter is an equality condition on the _id field { _id: <value> }.

Optional. The number of documents to return in the first batch. Defaults to 101. A batchSize of 0 means that the cursor will be established, but no documents will be returned in the first batch.

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

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.

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.

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.

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> }.

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> }.

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.

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

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.

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.