I hope it's not only me that can take start_time and finish_time ANYMORE!!!

Date or time ranges features. This provides extended and complex calculations over date and time ranges. In a few words, you can now store start_time and finish_time in the same column and relies on the methods provided here to fo your magic. PostgreSQL Docs

How it works

Migration

Create a table with the single column set as any type of time/date range (daterange, tsrange, or tstzrange), like:

create_table :events do |t|
  t.string   :name
  t.tsrange  :period
  t.interval :interval
end

Models

You have to go to each of your models and enable the functionality for each range-type field. The method name is defined on period.base_method.

# models/event.rb
class Event < ActiveRecord::Base
  period_for :period
end

There are a couple of important settings that can be provided to this:

# This means that nil value will be treated as false, the default is false, hence treated as true
period_for :period, pessimistic: true

# You can define a column or a value to be used as a threshold
period_for :period, threshold: :interval
period_for :period, threshold: 15.minutes

# This will force the creation of all the methods, which would raise an exception on conflicting. The default is false
period_for :period, force: true

# You can also rename any method that will be created
period_for :period, methods: { current: :ongoing, current?: :ongoing? }

You can check the list of the methods that will be created on the configuration page for period.method_names.

Scopes

This is where the period has its best features. With now provided Arel operators, a bunch of well-prepared statements can be used to query the records.

The default represents what was defined by the opposite of pessimistic option. If pessimistic is TRUE, then querying against NULL values will result in FALSE.

:current_on as .period_on(time)

It basically checks if the range contains the given value or arel attribute.

COALESCE(NULLIF("events"."period", tsrange(NULL,NULL)) @> value, default)
-- With threshold
COALESCE(NULLIF(tsrange(LOWER("events"."period") - "events"."interval",UPPER("events"."period") + "events"."interval"), tsrange(NULL,NULL)) @> value, default)

:current as .current_period

Checks if the period contains the current time/date.

COALESCE(NULLIF("events"."period", tsrange(NULL,NULL)) @> Time.zone.now, default)
 - With threshold -
COALESCE(NULLIF(tsrange(LOWER("events"."period") - "events"."interval",UPPER("events"."period") + "events"."interval"), tsrange(NULL,NULL)) @> Time.zone.now, default)

:not_current as .not_current_period

The opposite version of the :current scope.

NOT COALESCE(NULLIF("events"."period", tsrange(NULL,NULL)) @> Time.zone.now, default)
 - With threshold -
NOT COALESCE(NULLIF(tsrange(LOWER("events"."period") - "events"."interval",UPPER("events"."period") + "events"."interval"), tsrange(NULL,NULL)) @> Time.zone.now, default)

:containing as .period_containing(value)

Checks if the value contains in the range. You can pass either an Arel attribute or a plain value.

"events"."period" @> value

:not_containing as .period_not_containing(value)

The opposite version of the :containing scope.

NOT "events"."period" @> value1

:overlapping as .period_overlapping(left, right = nil)

Checks if two ranges overlap. You can pass either another range column as an Arel attribute, a plain range on the left, or the 2 parts of a range.

"events"."period" && value
 - OR -
"events"."period" && tsrange(left, right)

:not_overlapping as .period_not_overlapping(left, right = nil)

The opposite version of the :overlapping scope.

NOT "events"."period" && value
 - OR -
NOT "events"."period" && tsrange(left, right)

:starting_after as .period_starting_after(value)

Filter records that the left value is greater than the one provided, which can be either an Arel attribute or a plain value.

LOWER("events"."period") > value

:starting_before as .period_starting_before(value)

Filter records that the left value is less than the one provided, which can be either an Arel attribute or a plain value.

LOWER("events"."period") < value

:finishing_after as .period_finishing_after(value)

Filter records that the right value is greater than the one provided, which can be either an Arel attribute or a plain value.

UPPER("events"."period") > value

:finishing_before as .period_finishing_before(value)

Filter records that the right value is less than the one provided, which can be either an Arel attribute or a plain value.

UPPER("events"."period") < value

:real_containing as .period_real_containing(value) (ONLY WITH THRESHOLD)

Checks if the value contains in the range while considering the threshold. You can pass either an Arel attribute or a plain value.

tsrange(LOWER("events"."period") - "events"."interval",UPPER("events"."period") + "events"."interval") @> value

:real_overlapping as .period_real_overlapping(left, right = nil) (ONLY WITH THRESHOLD)

Checks if two ranges overlap while considering the threshold. You can pass either another range column as an Arel attribute, a plain range on the left, or the 2 parts of a range.

tsrange(LOWER("events"."period") - "events"."interval",UPPER("events"."period") + "events"."interval") && value
 - OR -
tsrange(LOWER("events"."period") - "events"."interval",UPPER("events"."period") + "events"."interval") && tsrange(left, right)

:real_starting_after as .period_real_starting_after(value) (ONLY WITH THRESHOLD)

Filter records that the left value with the threshold is greater than the one provided, which can be either an Arel attribute or a plain value.

(LOWER("events"."period") - "events"."interval") > value

:real_starting_before as .period_real_starting_before(value) (ONLY WITH THRESHOLD)

Filter records that the left value with the threshold is less than the one provided, which can be either an Arel attribute or a plain value.

(LOWER("events"."period") - "events"."interval") < value

:real_finishing_after as .period_real_finishing_after(value) (ONLY WITH THRESHOLD)

Filter records that the right value with the threshold is greater than the one provided, which can be either an Arel attribute or a plain value.

(UPPER("events"."period") + "events"."interval") > value

:real_finishing_before as .period_real_finishing_before(value) (ONLY WITH THRESHOLD)

Filter records that the right value with the threshold is less than the one provided, which can be either an Arel attribute or a plain value.

(UPPER("events"."period") + "events"."interval") < value

:containing_date as .period_containing_date(value) (NON DATERANGE ONLY)

Checks if the value contains in the range as date. You can pass either an Arel attribute or a plain value.

daterange(LOWER("events"."period")::date),UPPER("events"."period")::date) @> value
 - With threshold -
daterange((LOWER("events"."period") - "events"."interval")::date),(UPPER("events"."period") + "events"."interval")::date) @> value

:not_containing_date as .period_not_containing_date(value) (NON DATERANGE ONLY)

The opposite version of the :containing_date scope.

NOT daterange(LOWER("events"."period")::date),UPPER("events"."period")::date) @> value
 - With threshold -
NOT daterange((LOWER("events"."period") - "events"."interval")::date),(UPPER("events"."period") + "events"."interval")::date) @> value

:overlapping_date as .period_overlapping_date(left, right = nil) (NON DATERANGE ONLY)

Checks if two ranges overlap but comparing only dates. You can pass either another range column as an Arel attribute, a plain range on the left, or the 2 parts of a range.

daterange(LOWER("events"."period")::date),UPPER("events"."period")::date) && value
 - OR -
daterange(LOWER("events"."period")::date),UPPER("events"."period")::date) && daterange(left, right)
 - With threshold -
daterange((LOWER("events"."period") - "events"."interval")::date),(UPPER("events"."period") + "events"."interval")::date) && value
 - OR -
daterange((LOWER("events"."period") - "events"."interval")::date),(UPPER("events"."period") + "events"."interval")::date) && daterange(left, right)

:not_overlapping_date as .period_not_overlapping_date(left, right = nil) (NON DATERANGE ONLY)

The opposite version of the :overlapping_date scope.

NOT daterange(LOWER("events"."period")::date),UPPER("events"."period")::date) && value
 - OR -
NOT daterange(LOWER("events"."period")::date),UPPER("events"."period")::date) && daterange(left, right)
 - With threshold -
NOT daterange((LOWER("events"."period") - "events"."interval")::date),(UPPER("events"."period") + "events"."interval")::date) && value
 - OR -
NOT daterange((LOWER("events"."period") - "events"."interval")::date),(UPPER("events"."period") + "events"."interval")::date) && daterange(left, right)