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.

Starting in MongoDB 4.2, 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).

Changed in version 4.4. Prior to 4.4, comments could only be strings.

Optional. The cumulative time limit in milliseconds for processing operations on the cursor. MongoDB aborts the operation at the earliest following interrupt point.

Optional. Specifies the read concern.

Starting in MongoDB 3.6, 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.

Starting in MongoDB 4.2, 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.

Starting in MongoDB 4.2, 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. An internal command for replaying a replica set's oplog.

To use oplogReplay, the find field must provide a filter option comparing the ts document field to a timestamp using one of the following comparison operators:

• $gte

• $gt

• $eq

For example, the following command replays documents from the data capped collection with a timestamp later than or equal to January 1st, 2018 UTC:

{ find: "data",
  oplogReplay: true,
  filter: { ts: { $gte: new Timestamp(1514764800, 0) } } }

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.

Starting in MongoDB 4.4, if find (or subsequent getMore commands) returns partial results due to the unavailability of the queried shard(s), the output includes a partialResultsReturned indicator field.

If the queried shards are initially available for the find command but one or more shards become unavailable in subsequent getMore commands, only the getMore commands run when a queried shard or shards are unavailable include the partialResultsReturned flag in the 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 allowDiskUse to allow MongoDB to use temporary files on disk to store data exceeding the 100 megabyte memory limit while processing a non-indexed ("blocking") sort operation. If MongoDB requires using more than 100 megabytes of memory for a blocking sort operation, MongoDB returns an error unless the query specifies allowDiskUse. See Sort and Index Use for more information on blocking sort operations.

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.

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