Database table design for scheduling tasks

Question

I want to be able to create schedules that can be executed based on a fixed date, repeated daily, repeated on a particular day of the week, repeated on a particular month of the year, repeated on a particular date every year, and repeated at a particular time of the day.

Please how do i go about building the database tables for this problem?

Edit #1

Basically, i'm writing an application that allows users to schedule pre-configured greetings to be sent at various pre-configured times. I know i need a table that stores information about a schedule (ex. Christmas, Marketing One, ... | and when the schedule should run). Then another table to record what schedule has ran, what greeting it sent, to who, and what email; basically a transactions table.

My problem is designing the Schedule table because, i want to allow users run the schedule at a specific date, on a particular day of the week (recurring), on a particular day of every month, on a particular time everyday, and on a particular day/month (ex. 25/12) every year.

How can i create a set of tables for schedule that will take care of these inputs in flexible way?

Answer 1

Microsoft SQL Server has an efficient and flexible design: https://msdn.microsoft.com/en-us/library/ms178644.aspx?f=255&MSPPError=-2147217396

Answer 2

This is the table structure i came up with;

Schedule
 - ScheduleName
 - ScheduleTypeId (Daily, Weekly, Monthly, Yearly, Specific)
 - StartDate
 - IntervalInDays
 - Frequency
 - FrequencyCounter

ScheduleDaily
 - ScheduleDailyId 
 - ScheduleId
 - TimeOfDay
 - StartDate
 - EndDate

ScheduleMonthly
 - ScheduleMonthlyId
 - ScheduleId
 - DayOfMonth
 - StartDate
 - EndDate

ScheduleSpecific
 - ScheduleSpecificId
 - ScheduleId
 - SpecificDate
 - StartDate

...

ScheduleJob
 - ScheduleJobId
 - ScheduleId
 - ScheduleTypeId
 - RunDate
 - ScheduleStatusId

Answer 3

Since you are talking about schedules, I assume you want to build a batch application for management and execution of jobs.

You can check spring batch meta data design for a reference implementation. However, exact design would depend on your requirement. This is just a pointer.

Answer 4

I have read through the answers above and I think a lot of things are unnecessary, correct me if I'm wrong.

Here is what I think should be done:

Schedule

---

• Id

• type (Daily, monthly, weekly, fixed, yearly) - Enum

• frequency (Can be 1-7[days of week], 1-30(or 28)[days of month], 1-365[days of year] or null(for daily, fixed) - ArrayField(of ints) - [1, 7] OR [23] OR [235]OR null

• time (time of day in UTC) - ArrayField(of Char strings - ['9:00', '13:30']

• date (for fixed type) - datetime - 2009-03-21

• is_active (boolean) - for enabling, disabling the schedule

• name (CharField) - If you want to name the schedule

Rest of the fields would require context to what you are building.

Now, for this I'm thinking of running a cronjob every 30mins(I'm taking time input separated by 30mins) which runs a script(django management command in my case) which filters schedules from this table that need to be run:

Query would be something like this:

current_day_of_week = 3
current_day_of_month = 24
current_day_of_year = 114
current_time = 13:30
current_date = 2019-04-24

Filter records that match the below query(not even psuedo code)(I'm using Q objects(https://docs.djangoproject.com/en/2.2/topics/db/queries/#complex-lookups-with-q-objects)

Q(daily AND current_time) OR
Q(weekly AND current_day_of_week AND current_time) OR
Q(monthly AND current_day_of_month AND current_time) OR
Q(yearly AND current_day_of_year AND current_time) OR
Q(fixed AND current_date AND current_time)

Answer 5

To make your job easier, you could use an existing scheduler for the scheduling part. In Java there are for example Quartz or a library I wrote myself, db-scheduler.

db-scheduler is easily embeddable, and has out-of-the-box support for tasks on a recurring schedule (fixed duration, daily, etc). The execution-times are persisted in a single database table, so it survives restarts.