> Judging from the C++ source of the BSON implementation in MongoDB, I'd
> guess that the 'exception: wrong type for field (pipeline) 3 != 4' refers
> to the parser expecting either an Object (type == 3) and got an Array (type
> == 4) or the other way around.

> Which line of your Perl script throws the error?  If it's the "print
> Dumper(\@pipeline)" line, could you try "print Dumper-ing" just the
> $project and $group individually?  I'm guessing that your Mongo shell JSON
> to Perl translation might have an error, but after a quick glance, I don't
> quite see it.

> On Tuesday, November 13, 2012 5:03:20 PM UTC-5, Chris Matta wrote:

>> Sorry, documents look like this:

>> {
>>         "_id" : ObjectId("5097ffa800ba62343500f7ec"),
>>         "adaptor_id" : "DKA-2NL",
>>         "processor_id" : NumberLong(5),
>>         "datetime" : ISODate("2012-11-05T17:25:00Z"),
>>         "array_serial" : NumberLong(12345),
>>         "metric" : 26.989082,
>>         "processor_type" : "DKP"
>> }

>> On Tuesday, November 13, 2012 4:58:21 PM UTC-5, Chris Matta wrote:

>>> I'm trying to implement an aggregation function I've gotten to
>>> successfully work in javascript in perl, but I keep getting the error
>>> 'exception: wrong type for field (pipeline) 3 != 4'. Any ideas where I
>>> could be going wrong?

>>> my $project = Tie::IxHash->new(
>>>                         "year" => { '$year' => '$datetime'},
>>>                         "month" => {'$month' => '$datetime'},
>>>                         "day" => {'$dayOfMonth' => '$datetime'},
>>>                         "hour" => { '$hour' => '$datetime'},
>>>                         # the minute field is being rounded down to the
>>> nearest resolution
>>>                         "minute" => {'$subtract' => (
>>>                                             {'$minute' => '$datetime'},
>>>                                             {'$mod' => ({'$minute' =>
>>> '$datetime'}, $resolution)}
>>>                                                      )},
>>>                         array_serial => 1,
>>>                         adaptor_id => 1,
>>>                         processor_id => 1,
>>>                         processor_type => 1,
>>>                         metric => 1
>>>                 );

>>>     my $group = Tie::IxHash->new(
>>>                         _id => { array_serial => '$array_serial',
>>>                                 adaptor_id => '$adaptor_id',
>>>                                 processor_id => '$processor_id',
>>>                                 processor_type => '$processor_type',
>>>                                 year => '$year',
>>>                                 month => '$month',
>>>                                 day => '$day',
>>>                                 hour => '$hour',
>>>                                 minute => '$minute'
>>>                             },
>>>                         metric => {
>>>                             '$avg' => '$metric'
>>>                         }
>>>                 );

>>>     my @pipeline = (
>>>                     {'$match' => $query},
>>>                     {'$project' => $project},
>>>                     { '$group' => $group }
>>>                     );
>>>     print Dumper(\@pipeline);
>>>     my $aggregateCommand = Tie::IxHash->new(aggregate => $collection,
>>> pipeline => @pipeline);

>>>     my $result = $db->run_command($aggregateCommand);

>>>     print Dumper($result);