Bugs and strategies for PHP-driven MongoDB integer problems

The integer problem in this article, it's not MongoDB, it's a php-driven problem: The MongoDB itself has two integer types: 32-bit integers and 64-bit integers, but the older PHP driver, regardless of the operating system's 32-bit or 64-bit, treats all integers as 32-bit integers , resulting in 64-bit integers being truncated. In order to solve this problem as much as possible, the new PHP driver added the Mongo.native-long option, with a view to handling integers as 64 bits in 64-bit operating systems, with an interest in reference: 64-bit integers in MongoDB.

So does the PHP driver really solve the integer problem completely? no! also has bugs when handling group operations:

To illustrate the problem, let's start by generating some test data:

Ini_set (' Mongo.native_long ', 1);

$instance = new Mongo ();

$instance = $instance->selectcollection (' Test ', ' test ');

for ($i = 0; $i < $i + +) {

$instance->insert Array (

' group_id ' => rand (1, 5),

' Count ' => rand (1, 5),

));

}

?>

Let's use the group action, grouped by group_id, to summarize the count:

Ini_set (' Mongo.native_long ', 1);

$instance = new Mongo ();

$instance = $instance->selectcollection (' Test ', ' test ');

$keys = Array (' group_id ' => 1);

$initial = Array (' Count ' => 0);

$reduce = '

function (obj, prev) {

Prev.count + = Obj.count;

}

';

$result = $instance->group ($keys, $initial, $reduce);

Var_dump ($result);

?>

The results are not the same as expected, and the count does not accumulate, but instead becomes [object], and now if you must use group operations, there are two ways to mitigate this problem:

Ini_set (' Mongo.native_long ', 0);

$initial = Array (' Count ' => (float) 0);

Both of these methods are stopgap measures, since the current PHP driver in the implementation of the group is problematic, then we go around it, in other ways to achieve the same function, this way is MapReduce:

Ini_set (' Mongo.native_long ', 1);

$instance = new Mongo ();

$instance = $instance->selectdb (' Test ');

$map = '

function () {

Emit (this.group_id, this.count);

}

';

$reduce = '

function (key, values) {

var sum = 0;

For (var index in values) {

Sum + + Values[index];

}

return sum;

}

';

$result = $instance->command (Array (

' MapReduce ' => ' test ',

' Map ' => $map,

' Reduce ' => $reduce

));

$result = Iterator_to_array ($instance->{$result [' Result ']}->find ());

Var_dump ($result);

?>

It takes three steps to put an elephant in the fridge, and using mapreduce requires only map and reduce two steps, and here's a PDF document that graphically illustrates the correspondence between group by and MongoDB in MySQL: