Storing and searching opening/closing times for stores

Question

I'm writing an application that indexes data for our stores, some of which are open late (8 am - 2 am). We need to be able to search this database quickly -- basically, to run a query to find which stores are open at a given point in time (now, Sunday at 1 am, whatever).

In addition, the open/close times can vary day-by-day -- some stores are closed on Sundays, for example.

The obvious solution to me would be to make a table where I have a row with the store ID, day, open time, and close time. For something like Monday, 8 am - 2 am, that would actually be two rows, one for Monday 0800 - 2400, and one for Tuesday 0000 - 0200.

We have a lot of stores, so the search has to perform well (basically, the data has to be index-friendly), but I'll also have to display this data back out in a human-readable format. With my current solution, that'd look something like this:

Monday: 8:00 - Midnight Tuesday: Midnight - 2:00 am; 8:00 am - Midnight

I'm just wondering if anybody else has alternative solutions before I jump right to an implementation. Thanks!

Answer 1

When PBS (the US Public Broadcasting System) faced this same problem a couple of years ago, they invented the idea of the "30 hour day" -- Where 00:00 is midnight at the start of the day, 24:00 is midnight at the end of the day, 25:00 is 1am the next day, 30:00 is 6am the next day. That way Mon closing time of 26:00 is 2am Tues morning.

Rather than two records representing a single store's times for a day, it may be more object oriented to think of the "store day" as the object. That way 1 record = 1 store's times for a day. If you want to store the two sets of open/close times, just use four fields in the record instead of two--and adjust your queries appropriately.

Remember that your queries should use a library/api that you write and publish. The library will then deal with the data store and its data layout. No one but your library should be looking at the db directly.

Time zones are very important in this sort of app too. (Hopefully) at some point, the store chain will expand to cover more than one time zone. You'll then need to determine the local time of the query. -- May not the same as the time zone of your server which is handling the queries.

Further thoughts--

I now see that you're standardizing to GMT. Good. You could also use datetime values (vs time values) and standardize to a given week in time. Eg open time is Sun Jan 1, 1995 10am - Mon Jan 2, 1995 2am (using Jan 1, 1995 as a base since it was a Sunday).

Then rationalize your "current time and date" to match the same point in the week of Jan 1, 1995. Then query to find open store days.

HTH,

Larry