PHP Manual: Execute an aggregation pipeline command and retrieve results through a cursor

Description

public MongoCommandCursor MongoCollection::aggregateCursor ( array $command [, array $options ] )

With this method you can execute Aggregation Framework pipelines and retrieve the results through a cursor, instead of getting just one document back as you would with MongoCollection::aggregate. This method returns a MongoCommandCursor object. This cursor object implements the Iterator interface just like the MongoCursor objects that are returned by the MongoCollection::find method.

Note: The resulting MongoCommandCursor will inherit this collection's read preference. MongoCommandCursor::setReadPreference may be used to change the read preference before iterating on the cursor.

Parameters

pipeline

The Aggregation Framework pipeline to execute.

options

Options for the aggregation command. Valid options include:

"allowDiskUse"

Allow aggregation stages to write to temporary files
"cursor"

It is possible to configure how many initial documents the server should return with the first result set. The default initial batch size is 101. You can change it by adding the batchSize option:

<?php $collection->aggregateCursor( $pipeline, [ "cursor" => [ "batchSize" => 4 ] ] );

This option only configures the size of the first batch. To configure the size of future batches, please use the MongoCommandCursor::batchSize method on the returned MongoCommandCursor object.
"explain"

Return information on the processing of the pipeline. This option may cause the command to return a result document that is unsuitable for constructing a MongoCommandCursor. If you need to use this option, you should consider using MongoCollection::aggregate.
"maxTimeMS"
Specifies a cumulative time limit in milliseconds for processing the operation on the server (does not include idle time). If the operation is not completed by the server within the timeout period, a MongoExecutionTimeoutException will be thrown.

Return Values

Returns a MongoCommandCursor object. Because this implements the Iterator interface you can iterate over each of the results as returned by the command query. The MongoCommandCursor also implements the MongoCursorInterface interface which adds the MongoCommandCursor::batchSize, MongoCommandCursor::dead, MongoCommandCursor::info methods.

Examples

Example #1 MongoCollection::aggregateCursor example

Finding all of the distinct values for a key.


<?php
$m = new MongoClient;
$db = $m->test;
$people = $db->people;
$people->drop();

$people->insert(array("name" => "Joe", "points" => 4));
$people->insert(array("name" => "Molly", "points" => 43));
$people->insert(array("name" => "Sally", "points" => 22));
$people->insert(array("name" => "Joe", "points" => 22));
$people->insert(array("name" => "Molly", "points" => 87));

$ages = $people->aggregateCursor( [
        [ '$group' => [ '_id' => '$name', 'points' => [ '$sum' => '$points' ] ] ],
        [ '$sort' => [ 'points' => -1 ] ],
] );

foreach ($ages as $person) {
    echo "{$person['_id']}: {$person['points']}\n";
}

?>

The above example will output something similar to:

Molly: 130
Joe: 26
Sally: 22

Example #2 MongoCollection::aggregateCursor example with different initial batch size