2022 twenty-four merry days of Perl Feed

Catching dreams

Mango - 2022-12-05

Listening to dreams

During the year, some kids are writing "letters to Santa" or just sharing loudly what they want to "order" for Christmas, but it's not always the case... Sometimes kids are only dreaming what they want.

Normally, dreaming is not the most effective way to "order" a present for Christmas, but Santa has thought of everything. There is a special room in North Pole complex for this purpose. It's an all white, circular room with chairs arranged in the middle. Elves arrive at the room when it is nighttime in their assigned timezone.

They bring a pen and a notebook, and they listen to children's dreams and take notes.

Gathering notebooks

Elves capture notes on children's dreams all year long and, hence, approaching Christmas there are plenty of notebooks to put together and add to other wishes.

One of the elves had the idea to use MongoDB to store data.

Santa complained MongoDB was not Perl friendly (e.g. struggles with drivers...) and has a license that can be considered by some as "controversial"... But the elves are not disciplined and decided to go with it anyway.

1. First they installed MongoDB:

    $ sudo apt-get install mongodb

2. Then they started a shell:

    $ mongo
    MongoDB shell version v3.6.8
    connecting to: mongodb://
    MongoDB server version: 5.0.9

3. The elves created a new database:

    > use christmas2022
    switched to db christmas2022

Import dreams

Despite being undisciplined, the elves followed a convention in their notes and all of their notebooks are all well-formatted as CSV.

At the end of the night, a notebook looks like this:


It's easy to import these notes into MongoDB:

    $ mongoimport -d christmas2022 -c gifts --type csv --file gifts.csv --headerline
    2022-08-04T09:57:42.400+0200    connected to: mongodb://localhost/
    2022-08-04T09:57:42.408+0200    4 document(s) imported successfully. 0 document(s) failed to import.

And you can quickly verify that it is imported:

    > db.gifts.find()
    { "_id" : ObjectId("62eb96777d9a1bc25a68b25c"), "what" : "Transformer", "who" : "Billy", "where" : "Houston" }
    { "_id" : ObjectId("62eb96777d9a1bc25a68b25d"), "what" : "bicycle", "who" : "Tom", "where" : "Atlanta" }
    { "_id" : ObjectId("62eb96777d9a1bc25a68b25e"), "what" : "ball", "who" : "Ismail", "where" : "Atlanta" }
    { "_id" : ObjectId("62eb96777d9a1bc25a68b25f"), "what" : "Barbie", "who" : "Lisa", "where" : "Berlin" }

Using Perl to access dreams

To integrate this database in the North Pole code, the elves need to interact with it in Perl.

Let's install Mango:

    $ sudo cpanm Mango

Then they can access records with Perl methods:



use Mango ();
use feature qw( state );
sub mango { state $m = Mango->new('mongodb://localhost:27017') }

my $docs = mango->db('christmas2022')->collection('gifts')->find();

while (my $doc = $docs->next) {
    print "$doc->{what} for $doc->{who} in $doc->{where}\n";


And it produces this kind of output:

    Transformer for Billy in Houston
    bicycle for Tom in Atlanta
    ball for Ismail in Atlanta
    Barbie for Lisa in Berlin

Give me dreams from Atlanta

When it comes time for making deliveries, Santa is interested in having records from the same area to optimize the logistics of his delivery schedule.

With Mango, it's just a matter of adding a "clause" in the `find()` function:


my $docs = mango->db('christmas2022')->collection('gifts')->find({where => 'Atlanta'});


With the elves' copious year-round notetaking of children's dreams, Santa can count on the elves not to miss any of the children's wishes for Christmas.

Aided by Mango, Santa and the elves can handle the list easily and at end of December deliver something you only ever dreamed of!

Gravatar Image This article contributed by: Thibault DUPONCHELLE <thibault.duponchelle@gmail.com>