MongoCollection::getSlaveOkay
Here I am posting how I get tags from my documents. Documents should have 'tags' field which is array of strings:
{'tags':['php', 'mongo']}
<?php
$keys = array();
$initial = array('tags'=>array(), 'count'=>0);
$reduce = 'function (doc, total) { if (doc.tags.length) {doc.tags.forEach(function (e) {total.tags[e]=total.tags[e]||0; total.tags[e]++; total.count++;});} }';
$criteria = array(
'condition' => array(
'tags' => array('$exists'=>true)
),
);
?>
MongoCollection::group
(PECL mongo >=0.9.2)
MongoCollection::group — Performs an operation similar to SQL's GROUP BY command
Descripción
Parámetros
- 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.
-
Valores devueltos
Returns an array containing the result.
Ejemplos
Example #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']);
?>
El resultado del ejemplo sería algo similar a:
[{"category":"fruit","items":["apple","peach","banana"]},{"category":"veggie","items":["corn","broccoli"]}]
Example #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
$condition = array("a" => array( '$gt' => 1));
$g = $collection->group($keys, $initial, $reduce, $condition);
var_dump($g);
?>
El resultado del ejemplo sería algo similar a:
array(4) {
["retval"]=>
array(1) {
[0]=>
array(1) {
["count"]=>
float(1)
}
}
["count"]=>
float(1)
["keys"]=>
int(1)
["ok"]=>
float(1)
}
Example #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++; }'));
?>
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User Contributed Notes
MongoCollection::group
Evgeniy Abduzhapparov
12-Nov-2010 01:05