Laravel: Filter collection on property, with a twist

Question

I am looking for an elegant (and comprehensible in a year's time) solution for a collection filtering challenge. I am querying a log database and get some sort of the following data structure

| refId   | isDeleted   | loggedDate          |
|---------|-------------|---------------------|
| 1       | 0           | 2018-02-23 21:39:05 |
| 2       | 0           | 2018-02-23 21:39:05 |
| 3       | 0           | 2018-02-23 21:39:05 |
| 4       | 0           | 2018-02-23 21:39:05 |
| 2       | 1           | 2018-02-23 21:49:05 |
| 5       | 0           | 2018-02-23 21:49:05 |
| 6       | 1           | 2018-02-23 21:49:05 |

My objective is to filter out the entries which have both, isDeleted=0 && isDeleted=1, and to leave only those which are either isDeleted=0 or isDeleted=1. In this example I should end up with datasets of 1, 3, 4, 5 and 6.

Thx.

PS. The collection might hold up to 1000 entries, if you were to ask...

Answer 1

Thanks to Don't Panic advice, I've come up with the following chain.

$collection->groupBy('refId')
                ->filter( function($refGroup) {
                    if ( $refGroup->count() > 1 ) {

                        # 0 + 1
                        $length = $refGroup->count();
                        $sum = $refGroup->reduce(function($carry, $item){
                            return $carry + $item->isDeleted;
                        });

                        # all sum=0 refIds are OK (no deletions)
                        if ( $sum == 0 ) {
                            return $refGroup;
                        } else {
                            # all sum=1 are good if the length=1 (deleted once)
                            if ( $length == $sum ) {
                                return $refGroup;
                            } else {
                                # sum=1 and length more than 1? manipulated and deleted => ignore
                                return false;
                            }
                        }

                    } else {
                        return $refGroup;
                    }
                })
                ->flatten(1)
                ->unique('refId');

The first tests are OK. Will need to test it with different datasets, though.

Answer 2

Maybe you could group by refId and isDeleted and filter the groups that only have one entry.

$refIds = $collection->groupBy(['refId', 'isDeleted'])->filter(function($refGroup) {
    return count($refGroup) === 1;
});

I can't currently test this to verify it works, I just tried to come up with an approximation for how I would do this in SQL based on the Laravel docs.

The result would still be grouped though, so it might not be that handy depending on how you're using it.