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Class AggregationCursor<TSchema>

The AggregationCursor class is an internal class that embodies an aggregation cursor on MongoDB allowing for iteration over the results returned from the underlying query. It supports one by one document iteration, conversion to an array or can be iterated as a Node 4.X or higher stream

Type Parameters

  • TSchema = any

Hierarchy

Index

Constructors

Methods

Properties

Events

Accessors

Constructors

constructor

Methods

Static once

Static on

Static listenerCount

bufferedCount

  • bufferedCount(): number

  • Returns current buffered documents length

    Returns number

readBufferedDocuments

  • readBufferedDocuments(number?: number): TSchema[]

  • Returns current buffered documents

    Parameters

    • Optional number: number

    Returns TSchema[]

[asyncIterator]

stream

hasNext

  • deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Returns Promise<boolean>

  • deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Parameters

    Returns void

next

  • Get the next available document from the cursor, returns null if no more documents are available.

    deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Returns Promise<TSchema>

  • deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Parameters

    Returns void

  • deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Parameters

    Returns void | Promise<TSchema>

tryNext

  • Try to get the next available document from the cursor or null if an empty batch is returned

    deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Returns Promise<TSchema>

  • deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Parameters

    Returns void

forEach

  • forEach(iterator: ((doc: TSchema) => boolean | void)): Promise<void>
  • forEach(iterator: ((doc: TSchema) => boolean | void), callback: <internal>.Callback<void>): void

  • Iterates over all the documents for this cursor using the iterator, callback pattern.

    If the iterator returns false, iteration will stop.

    Parameters

    • iterator: ((doc: TSchema) => boolean | void)

      The iteration callback.

        • (doc: TSchema): boolean | void

        • Parameters

          • doc: TSchema

          Returns boolean | void

    Returns Promise<void>

  • deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Parameters

    • iterator: ((doc: TSchema) => boolean | void)
        • (doc: TSchema): boolean | void

        • Parameters

          • doc: TSchema

          Returns boolean | void

    • callback: <internal>.Callback<void>

    Returns void

close

  • deprecated

    options argument is deprecated. Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Returns Promise<void>

  • deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Parameters

    Returns void

  • deprecated

    options argument is deprecated

    Parameters

    Returns Promise<void>

  • deprecated

    options argument is deprecated. Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Parameters

    Returns void

toArray

  • Returns an array of documents. The caller is responsible for making sure that there is enough memory to store the results. Note that the array only contains partial results when this cursor had been previously accessed. In that case, cursor.rewind() can be used to reset the cursor.

    Returns Promise<TSchema[]>

  • deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Parameters

    Returns void

addCursorFlag

  • addCursorFlag(flag: "tailable" | "oplogReplay" | "noCursorTimeout" | "awaitData" | "partial" | "exhaust", value: boolean): AggregationCursor<TSchema>

  • Add a cursor flag to the cursor

    Parameters

    • flag: "tailable" | "oplogReplay" | "noCursorTimeout" | "awaitData" | "partial" | "exhaust"

      The flag to set, must be one of following ['tailable', 'oplogReplay', 'noCursorTimeout', 'awaitData', 'partial' -.

    • value: boolean

      The flag boolean value.

    Returns AggregationCursor<TSchema>

withReadPreference

withReadConcern

maxTimeMS

  • Set a maxTimeMS on the cursor query, allowing for hard timeout limits on queries (Only supported on MongoDB 2.6 or higher)

    Parameters

    • value: number

      Number of milliseconds to wait before aborting the query.

    Returns AggregationCursor<TSchema>

batchSize

rewind

  • rewind(): void

  • Rewind this cursor to its uninitialized state. Any options that are present on the cursor will remain in effect. Iterating this cursor will cause new queries to be sent to the server, even if the resultant data has already been retrieved by this cursor.

    Returns void

clone

  • Returns a new uninitialized copy of this cursor, with options matching those that have been set on the current instance

    Returns AggregationCursor<TSchema>

map

  • Map all documents using the provided function If there is a transform set on the cursor, that will be called first and the result passed to this function's transform.

    remarks

    Note Cursors use null internally to indicate that there are no more documents in the cursor. Providing a mapping function that maps values to null will result in the cursor closing itself before it has finished iterating all documents. This will not result in a memory leak, just surprising behavior. For example:

    const cursor = collection.find({});
    cursor.map(() => null);

    const documents = await cursor.toArray();
    // documents is always [], regardless of how many documents are in the collection.

    Other falsey values are allowed:

    const cursor = collection.find({});
    cursor.map(() => '');

    const documents = await cursor.toArray();
    // documents is now an array of empty strings

    Note for Typescript Users: adding a transform changes the return type of the iteration of this cursor, it does not return a new instance of a cursor. This means when calling map, you should always assign the result to a new variable in order to get a correctly typed cursor variable. Take note of the following example:

    Type Parameters

    • T

    Parameters

    • transform: ((doc: TSchema) => T)
        • (doc: TSchema): T

        • Parameters

          • doc: TSchema

          Returns T

    Returns AggregationCursor<T>

explain

  • Execute the explain for the cursor

    deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Returns Promise<<internal>.Document>

  • deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Parameters

    Returns Promise<<internal>.Document>

  • deprecated

    Callbacks are deprecated and will be removed in the next major version. See mongodb-legacy for migration assistance

    Parameters

    Returns void

group

  • Add a group stage to the aggregation pipeline

    Type Parameters

    • T = TSchema

    Parameters

    Returns AggregationCursor<T>

limit

  • Add a limit stage to the aggregation pipeline

    Parameters

    • $limit: number

    Returns AggregationCursor<TSchema>

match

out

  • Add an out stage to the aggregation pipeline

    Parameters

    • $out: string | { db: string; coll: string }

    Returns AggregationCursor<TSchema>

project

  • Add a project stage to the aggregation pipeline

    remarks

    In order to strictly type this function you must provide an interface that represents the effect of your projection on the result documents.

    By default chaining a projection to your cursor changes the returned type to the generic Document type. You should specify a parameterized type to have assertions on your final results.

    example
    // Best way
    const docs: AggregationCursor<{ a: number }> = cursor.project<{ a: number }>({ _id: 0, a: true });
    // Flexible way
    const docs: AggregationCursor<Document> = cursor.project({ _id: 0, a: true });
    remarks

    In order to strictly type this function you must provide an interface that represents the effect of your projection on the result documents.

    Note for Typescript Users: adding a transform changes the return type of the iteration of this cursor, it does not return a new instance of a cursor. This means when calling project, you should always assign the result to a new variable in order to get a correctly typed cursor variable. Take note of the following example:

    example
    const cursor: AggregationCursor<{ a: number; b: string }> = coll.aggregate([]);
    const projectCursor = cursor.project<{ a: number }>({ _id: 0, a: true });
    const aPropOnlyArray: {a: number}[] = await projectCursor.toArray();

    // or always use chaining and save the final cursor

    const cursor = coll.aggregate().project<{ a: string }>({
      _id: 0,
      a: { $convert: { input: '$a', to: 'string' }
    }});

    Type Parameters

    Parameters

    Returns AggregationCursor<T>

lookup

redact

skip

  • Add a skip stage to the aggregation pipeline

    Parameters

    • $skip: number

    Returns AggregationCursor<TSchema>

sort

  • Add a sort stage to the aggregation pipeline

    Parameters

    Returns AggregationCursor<TSchema>

unwind

  • Add a unwind stage to the aggregation pipeline

    Parameters

    Returns AggregationCursor<TSchema>

geoNear

addListener

on

once

removeListener

off

removeAllListeners

  • removeAllListeners<EventKey>(event?: string | symbol | EventKey): AggregationCursor<TSchema>

listeners

rawListeners

emit

listenerCount

  • listenerCount<EventKey>(type: string | symbol | EventKey): number

  • Type Parameters

    • EventKey extends "close"

    Parameters

    • type: string | symbol | EventKey

    Returns number

prependListener

prependOnceListener

eventNames

  • eventNames(): string[]

getMaxListeners

  • getMaxListeners(): number

setMaxListeners

Properties

Static Readonly errorMonitor

errorMonitor: typeof errorMonitor

This symbol shall be used to install a listener for only monitoring 'error' events. Listeners installed using this symbol are called before the regular 'error' listeners are called.

Installing a listener using this symbol does not change the behavior once an 'error' event is emitted, therefore the process will still crash if no regular 'error' listener is installed.

Static Readonly captureRejectionSymbol

captureRejectionSymbol: typeof captureRejectionSymbol

Static captureRejections

captureRejections: boolean

Sets or gets the default captureRejection value for all emitters.

Static defaultMaxListeners

defaultMaxListeners: number

Events

Static Readonly CLOSE

CLOSE: "close"

Accessors

id

  • Returns Long

namespace

  • Returns MongoDBNamespace

readPreference

  • Returns ReadPreference

readConcern

  • Returns ReadConcern

closed

  • get closed(): boolean

  • Returns boolean

killed

  • get killed(): boolean

  • Returns boolean

loadBalanced

  • get loadBalanced(): boolean

  • Returns boolean

pipeline

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