Question

I have a DataMapper based SQLite database. I store the time at which the data upon which the model is built as Msrun.rawtime or a property :rawtime, DateTime, of the Model Msrun.

What I need to be able to do is select a date/time range in a filter, and then sort the DataMapper entries according to that time filter. Like this:

Msrun.all.size # => 63
matches = Msrun.all( begintime: 2010-11-03T21:33:00-0600, endtime: 2011-04-09T23:59:59-0600 )
matches.size # => 12

As my database has ~500 properties between this and submodels, and I expect to generate ~100 of these entries per month, I would like something that is really fast too. Is that going to require SQL? Is this possible? Am I making this harder than it should be/is there an easier way to configure my data to enable this type of sort?

Answer 1

I’m not sure what is you want to do? If you want to query for items that happen between a particular start and end time, you can use:

Mrsun.all(:rawtime => start_time..end_time)

This will generate SQL something like

SELECT ... FROM msruns WHERE rawtime > start_time AND rawtime < end_time;

Does that answer your question?

A fuller example:

require 'rubygems'
require 'dm-core'
require 'dm-migrations'


# setup the logger
DataMapper::Logger.new($stdout, :debug)

# connect to the DB
DataMapper.setup(:default, 'sqlite3::memory:')

class Msrun
  include DataMapper::Resource

  # properties
  property :id, Serial
  property :rawtime, DateTime

end

DataMapper.finalize.auto_migrate!


10.times do |n|
  Msrun.create(:rawtime => DateTime.new(2011, 1, 1, 0, 0 , n))
end

p Msrun.all(:rawtime => DateTime.parse('2011-1-1T00:00:04+0100')..DateTime.parse('2011-1-1T00:00:07+0100'))