Say i have multiple tables (models) and I need to select an item in one table, and all of the data in the other models to get a compete row.
What's the best way to join them so that I get the data I need in one query?
I know I can say:
p = Person.find_by_id(100, :include => [ :books]);
If Person and Book have a "has_many" relationship, But what if Person has Books and Books has a has_many relationship to Categories and I want both models to be loaded at the same time?
This is easy in other languages, but what's the proper "Rails way" of doing this?
Within reason - the database query gets a little more gnarly each
time. You might also eventually run into limits on the number of
joins allowed in a single query
You also want to be careful when loading multiple sibling has_many, eg
If a person had 100 books and 100 magazines then this would end up
with rails handling 10000 rows of results (100x100), which it
currently does so in a not very speedy way.
True, nothing is free, but within reason, this works very well. I do
wish there was a way to limit the columns returned through select, and
from what I have read, that is a future planned feature, but
unfortunately, currently, you get every column from all tables. When he
said indefinitely, I assumed he realized that building 10,000 objects
would take a bit of time, but I guess I assume a little to much
sometimes.
I do wish there was a way to limit the columns returned through select, and from what I have read, that is a future planned feature, but unfortunately, currently, you get every column from all tables.
I do
wish there was a way to limit the columns returned through select,
and
from what I have read, that is a future planned feature, but
unfortunately, currently, you get every column from all tables.
