问题
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?
回答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.
回答2:
You can use genuine SQL relational databases from Google appengine apps, through a webservice.
One such webservice is Rdbhost, at http://www.rdbhost.com .
It involves its compromises, particularly speed, in that each page view requires another backend http page request to the db server, but it allows you to use the SQL design knowledge you already have.
来源:https://stackoverflow.com/questions/731147/what-changes-do-i-need-for-my-tables-to-work-on-appengines-bigtable