How to get returned data from mongoDB in Perl?

Question

I read http://api.mongodb.org/perl/current/MongoDB/Examples.html and seems to be only documentation from mongoDB on Perl. How do I get my query result from mongoDB in perl. Let us say into Hash. I have successfully made connection to the db so far. I managed to do inserts into collections. Now how do I issue select query and get its returned data into hash or something similar?

Update:

Example of my data
{
 "_id" : ObjectId("asdhgajsdghajgh"),
 "country" : "USA"
 "city" : "Boston"
}

{
 "_id" : ObjectId("asdhgajsdghajgh"),
 "country" : "USA"
 "city" : "Seattle"
}

{
 "_id" : ObjectId("asdhgajsdghajgh"),
 "country" : "Canada"
 "city" : "Calgary"
}

My code

my $cursor = $my_collection
    ->find({ country => 1 }) 
    ;
while (my $row = $cursor->next) {
    print "$row\n";
}

This code is not resulting any output. I want to basically iterate through the entire collection and read document by document. Not sure what I am doing wrong. I used the code above. I changed $cur->next to $cursor->next I am guessing it was a typo. I appreciate all the answers so far.

The stuff on api.mongodb.org is out of date. You should look at CPAN. I've updated the Perl link on api.mongodb.org to point there. — friedo
– friedo, Commented Jan 16, 2013 at 1:35

creaktive · Accepted Answer · 2013-01-16 23:18:17Z

10

That's not the official documentation. Head right to the CPAN:

Iterating results is pretty similar to the DBI way:

use Data::Printer;
use MongoDB;

# no query is performed on initialization!
my $cursor = $collection
    ->find({ active => 1, country => 'Canada' }) # filter "active" records from Canada
    ->sort({ stamp => -1 }) # order by "stamp" attribute, desc.
    ->limit(1000);          # first 1000 records

# query & iterate
while (my $row = $cur->next) {
    # it is 'p', from Data::Printer!
    p $row;
}

edited Jan 16, 2013 at 23:18

answered Jan 15, 2013 at 23:34

creaktive

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5 Comments

DoodleKana Over a year ago

Thanks for the reply. I read some of the documentation above and it helped me to understand how to get the result which is pretty straight forward like my $some_users = $users->find({"name" => "Joe"}); This example does not explain what happens when find() returns millions of results? How do I iterate through those results?

creaktive Over a year ago

Sorry, added the iterator example!

DoodleKana Over a year ago

thanks guys for your answers. I updated my question again. Can you guys check and see why my code is not resulting in any output. I am guessing it is a very simple noob mistake.

creaktive Over a year ago

Edited the answer! Oops, it's not print, it's just p! You have to install Data::Printer, though. Also, country => 1 will search for country with numeric value of 1. It won't return anything in your case.

DoodleKana Over a year ago

quick reply Thanks. I found out what I was looking for finally. my $cursor = $my_collection->find;while (my $row = $cursor->next) {print $row->{'country'}} This worked

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