How do I remove an element in an array based on content? - perl

Question

I am working with MongoDB and Perl. Here is my data structure:
{
"_id" : ObjectId("501976f8005c8b541d000000"),
"err_id" : "err",
"solution" : [
{
"attachment" : "attach",
"macr" : "macrs",
"yammer" : "yam",
"resolution" : "l",
"salesforce" : "salesforce",
"username" : "bob"
},
{
"attachment" : "attach",
"macr" : "macrs",
"yammer" : "yam",
"resolution" : "losssss",
"salesforce" : "salesforce",
"username" : "bob"
}
]
}
As you can see, I have an array with objects inside. I have created this using the Perl MongoDB library.
I am familiar with some syntax for manipulating arrays in the Perl MongoDB lib. For example, I use this to find entries with a username the same as $username.
$users->find({"solution.username" => $username});
I thought removing an element would be as simple:
$users->remove({"solution.username" => $username});
But alas, it is not so. I have tried this and using pull, but to no avail! I've had a hard time finding this. Does anybody know the syntax to remove an array element based on the contents of one of its fields?

Answer 1

The MongoDB::Collection remove() method will remove documents matched by your query .. so definitely not what you are looking for.
To delete specific fields you should use $unset.
Your solution.usernames are actually in an array, so you would have to include an array index for the fields to delete, eg:
$users->update({"_id" => '123'}, {
'$unset' => {
'solution.0.username' => 1,
'solution.1.username' => 1
}
});
I'm not aware of a shorter syntax to unset all fields matching username within the solution array, but you can add multiple solution.#.username fields to the $unset command.
My example above deletes the first two username entries from the array. If the matching document(s) had more than two username entries, each time you ran this update you would delete up to two more entries (if they exist).