Question

Let’s say I have a booking database consisting of users:

user_id fname lname 

and their tickets

ticket_id user_id flight_no 

and associated flights

flight_no airline departure_time arrival_time 

What would I need to change to move this Google AppEngine?

I understand AppEngine doesn’t allow joins.

Does that mean my table should become one big schmudge of fields all lumped together?

bookings:

user_id fname lname ticket_id flight_no airline departure_time arrival_time 

In other words, all of my queries now run against the same table?

Answer 1

What changes you need depends mostly on what queries you need to run, not on what data you have. Most likely you will only have to add a couple of things.

Make a list of queries and then take a look at Restrictions on Queries. After you’ve found the problematic ones, try to rewrite them with BigTable’s constraints in mind.

For example, if you often need to find the number of tickets for a list of flights, you won’t just be able to do:

 SELECT     flight_no, COUNT(*) FROM     flights JOIN     tickets ON tickets.flight_no = flights.flight_no GROUP BY     flight_no 

So you’ll need to add a counter of tickets to flights and increment/decrement that when creating/deleting tickets.

Good side of this is that BigTable forces you to have a very scalable database design. Bad side is that it wastes a lot of your time when you don’t really need a scalable design.