MongoDB PHP使用条件聚合数据

Question

I have 2 different pipelines: with condition

$pipeline = array(
            array('$match' => array(
                'currentStep' => 'CREATE')),
            array('$group' => array(
                '_id' => '$name',
                'value' => array('$sum' => 1)
            )));

and without

$pipeline = array(
            array('$group' => array(
                '_id' => '$name',
                'value' => array('$sum' => 1)
            )));

How combine them in one single $pipeline in order to get such output:

_id - value_with_match_condition - value_without

Answer 1

In order to do this, you will need to combine the use of $sum with $cond. For instance, it might look something like this:

$pipeline = array(
    array('$group'=>array(
        '_id'=>'$name',
        'sum_matching'=>array(
            '$sum'=>array('$cond'=>array(
                'if'=>array('$eq'=>array('$currentStep', 'CREATE')),
                'then'=>1,
                'else'=>0
            )),
        ),
        'sum_all'=>array('$sum'=>1)
    ))
);

This is untested, but something matching this general form should work.