On 12 October 2014 11:54, Colin Law <[email protected]> wrote: > On 12 October 2014 11:34, Yongbiao Long <[email protected]> wrote: >> On Sun, Oct 12, 2014 at 5:17 PM, Colin Law <[email protected]> wrote: >>> Are you sure your basic design is appropriate? Having 100,000 >>> associated records per user seems very high. Are you able to explain >>> what is in those records in case an alternative can be suggested? >> >> Thank you Colin! I'm implementing a railway ticket-booking system just >> for learn purpose, not for production. >> Now I try to explain it: >> Suppose a train has 20 stations along the way. It has 1000 seats to >> sell. Table A store one train's information in a row. I want table B >> to store every seat's information. I design table B as follow >> >> train_id: >> start_city_id: >> end_city_id: >> seat_id: >> availability: boolean type >> date: >> >> For one train, the number of start_city_id and end_city_id's >> combinations is 19+18+...+1=190, the number of possible date is >> 20(people can book tickets in 20 days), and possible seat_id's number >> is 1000. The total number of rows for one train is >> 190*1000*20=3,800,000. So huge.. > > The first point is that you should only add rows as seats are booked, > use that fact that there is no row to indicate that there is no > booking. > Secondly, what is the date? Is that the date of the journey or the > date of the booking? I don't understand why you have multiplied the > number of trains by 20 days. If it is the date of the journey then > consider having a Journeys table which is a particular train on a > particular day. > Thirdly I don't understand why you have 20 factorial for the city > combinations. Is it not true that if a seat is booked from station 1 > to station 3 then that implies a booking 1 to 2 and 2 to 3? In which > case you do not separate rows for bookings 1 to 2, 2 to 3, and 1 to 3.
In fact thinking further, I would probably turn the problem around and have a bookings table, specifying the journey, the stations, and the seat (or seats). Colin -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/rubyonrails-talk/CAL%3D0gLv77Kt-sH6rw0djfqrkNUycnkTimEw6anNg_oZSg-YOYg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
