Performs an operation similar to SQL's GROUP BY command


(PECL mongo >=0.9.2)

MongoCollection::groupPerforms an operation similar to SQL's GROUP BY command

Описание

public array MongoCollection::group ( mixed $keys , array $initial , MongoCode $reduce [, array $options = array() ] )

Список параметров

keys

Fields to group by. If an array or non-code object is passed, it will be the key used to group results.

1.0.4+: If keys is an instance of MongoCode, keys will be treated as a function that returns the key to group by (see the "Passing a keys function" example below).

initial

Initial value of the aggregation counter object.

reduce

A function that takes two arguments (the current document and the aggregation to this point) and does the aggregation.

options

Optional parameters to the group command. Valid options include:

  • "condition"

    Criteria for including a document in the aggregation.

  • "finalize"

    Function called once per unique key that takes the final output of the reduce function.

  • "maxTimeMS"

    Указывает суммарный лимит времени в миллисекундах на обработку операции (не включая время простоя). Если операция не завершилась за это время, то бросается MongoExecutionTimeoutException.

Возвращаемые значения

Returns an array containing the result.

Список изменений

Версия Описание
1.5.0 Added "maxTimeMS" option.
1.2.11 Emits E_DEPRECATED when options is scalar.

Примеры

Пример #1 MongoCollection::group() example

This groups documents by category and creates a list of names within that category.

<?php

$collection
->insert(array("category" => "fruit""name" => "apple"));
$collection->insert(array("category" => "fruit""name" => "peach"));
$collection->insert(array("category" => "fruit""name" => "banana"));
$collection->insert(array("category" => "veggie""name" => "corn"));
$collection->insert(array("category" => "veggie""name" => "broccoli"));

$keys = array("category" => 1);

$initial = array("items" => array());

$reduce "function (obj, prev) { prev.items.push(obj.name); }";

$g $collection->group($keys$initial$reduce);

echo 
json_encode($g['retval']);

?>

Результатом выполнения данного примера будет что-то подобное:

 [{"category":"fruit","items":["apple","peach","banana"]},{"category":"veggie","items":["corn","broccoli"]}] 

Пример #2 MongoCollection::group() example

This example doesn't use any key, so every document will be its own group. It also uses a condition: only documents that match this condition will be processed by the grouping function.

<?php

$collection
->save(array("a" => 2));
$collection->save(array("b" => 5));
$collection->save(array("a" => 1));

// use all fields
$keys = array();

// set intial values
$initial = array("count" => 0);

// JavaScript function to perform
$reduce "function (obj, prev) { prev.count++; }";

// only use documents where the "a" field is greater than 1
$condition = array('condition' => array("a" => array( '$gt' => 1)));

$g $collection->group($keys$initial$reduce$condition);

var_dump($g);

?>

Результатом выполнения данного примера будет что-то подобное:

 array(4) {   ["retval"]=>   array(1) {     [0]=>     array(1) {       ["count"]=>       float(1)     }   }   ["count"]=>   float(1)   ["keys"]=>   int(1)   ["ok"]=>   float(1) } 

Пример #3 Passing a keys function

If you want to group by something other than a field name, you can pass a function as the first parameter of MongoCollection::group() and it will be run against each document. The return value of the function will be used as its grouping value.

This example demonstrates grouping by the num field modulo 4.

<?php

$c
->group(new MongoCode('function(doc) { return {mod : doc.num % 4}; }'),
     array(
"count" => 0),
     new 
MongoCode('function(current, total) { total.count++; }'));

?>