Rails: combine two queries into one

Question

I am new to rails. Here is the following code with Foo as model object:

a = Foo
a = Foo.where(age: 18)
if params[:sort] == "desc"
  a = a.order("name desc") 
end

Here two queries are performed, I want to combine them to one or you can say i want to perform Foo.where(age=18).order("name asc")

Remember there can be the case when order is no needed i.e. params[:sort] is not equal to desc.

Please don't give solution like

if params[:sort] == "desc"
    a = a.where(age=18).order("name desc") 
else
    a = a.where(age=18)
end

as it makes code redundant and also for more parameters it might not work.

side note: IMHO re-using name variables is not a good programming practice. Create new variables with meaningful names as you go along, it's much easier to follow the function (and debug it). — tokland, Aug 03 '12 at 07:40
Also, what's up with `where(age=18)`? Shouldn't it be `where(age: 18)` or `where("age=18")`? — Sergio Tulentsev, Aug 03 '12 at 07:44

score 5 · Accepted Answer · answered Aug 03 '12 at 07:38

5

No, you're mistaken. Actually, no queries are performed here.

a = Foo
a = Foo.where(age=18)
if params[:sort] == "desc"
  a = a.order("name desc") 
end

The actual query is sent where you start retrieving data. That is, do something like

a.each do |b|
  # do something with b
end

Until then you can safely chain criteria building methods (where, order, select and others).

answered Aug 03 '12 at 07:38

Sergio Tulentsev

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may be you are right but when i look at console it shows me two queries. – Paritosh Singh Aug 03 '12 at 07:40
Maybe you do something else. Can you double check that? – Sergio Tulentsev Aug 03 '12 at 07:41
Hey i think you are right, its me only who got mistaken, rather than controller i should look for problem in views. thanks :) – Paritosh Singh Aug 03 '12 at 07:48

score 0 · Answer 2 · answered Aug 03 '12 at 07:39

0

Actually your code will only execute one query. this is because in rails the calls to the database are only done once you access the result. So when you will write a.first (or something similar) it will make the DB call.

answered Aug 03 '12 at 07:39

davidrac

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score 0 · Answer 3 · answered Aug 03 '12 at 07:39

0

If its that what you mean... A simple solution would be:

a.where(age: 18).order("name #{params[:sort] || 'asc'}")

So if params[:sort] is nil it will default to asc.

answered Aug 03 '12 at 07:39

spas

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Rails: combine two queries into one

3 Answers3