How to order data by ONLY Hour:Minute format in MongoDB/Mongoid? (Without date!)

Question

I'm using MongoDB and Mongoid in my project. I have some difficulties with ordering "Time" field data.

As you know, eventhough you set a field type as Time inside your Mongoid Document, time data is stored as this format (note that I use +2 hours offset to get my own timezone's time instead of UTC):

Mon, 31 Dec 2012 08:30:00 EET +02:00

I'm not sure if I'm missing something but this is what happens to me.

I want to use that Time data inside one of my views. I need to sort some related stuff by ONLY Hour:Minute format. I don't want Rails to take care of the DATE part of the field data. Because whenever a new Time record inserted to DB, it takes the day info as CURRENT DAY.

Issue is:

Because of it saves CURRENT DAY for each of new Time records, when I try to order_by("hour DESC") NEW records always retrieved first eventhough HOUR part of the data is bigger!

For example:

First data:
=> Tue, 27 Nov 2012 19:50:00 EET +02:00
Second data:
=> Mon, 24 Dec 2012 18:45:00 EET +02:00

As you know, normally, 19:50 is bigger than 18:45. But in this scenario, because of Rails takes day info into calculation, 18:45 looks like bigger than 19:50!

So what is the work around for this issue?

Thanks in advence.

Answer 1

I've found an answer to this at Mongoid's issues list: https://github.com/mongoid/mongoid/issues/1169

That's really weired...

If I understood well, Time field type is totally useless! What is the difference between DateTime and Time then??

You even can not compare hours and minutes ONLY inside a Time field.

And hold your breath for the work around...

Solution is:

Not to use Time field type! Just use String and compare hours and dates via that procedure.

Person.where(:time.gt => "13:00")

If some could explain this weired situation, I would be happy.