Re: How complex a query can ActiveRecord handle before it''s better using Raw SQL or a View???

Frederick Cheung
Fri, 19 Dec 2008 02:13:39 -0000

On 19 Dec 2008, at 02:01, Greg Hauptmann wrote:

> I was asking I guess from the point of view of:
> (a) maintainability/readability of the code (i.e. keeping things
> simple) and

I don''t think how complex is the right question. There are some very
complex things you can generate very easily, as well as easier things
where you might have to fight activerecord.
>
> (b) to a lesser extent performance (i.e. if ActiveRecord wasn''t
> going to be good at handling a complex query well from a performance
> point of view)
That''s sort of what I started with. Performance wise, Active Record is
only going to care about the size of the result set really. After all
it''s the database, not active record that has to do the 27 joins or
whatever it is.

Fred



> On Fri, Dec 19, 2008 at 11:48 AM, Frederick Cheung
<frederick.cheung-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
> > wrote:
>
>
> On 19 Dec 2008, at 01:25, Greg Hauptmann wrote:
>
> > Hi,
> >
> > How complex a query can ActiveRecord handle before it''s
better using
> > Raw SQL or a View???
> >
> Depends what you mean by handle. If you mean "will ruby run out of
> steam" then that''s purely a function of the result set,
instantiating
> 1 million ActiveRecord objects is probably not a good idea.
> If you mean handle as in get ActiveRecord to generate it without
> writing any sql yourself then I don''t believe there''s a
hard and fast
> rule or anything like that.
> You might be able to get away with
>
> Transaction.find :all, :joins => [:category, {:allocation
> => :person}],
>                       :conditions => {''people.id''
=> bob,
> ''categories.tax_id'' =>
> 1234, ''transactions.created_at'' => (1.week.ago ..
Time.now)}
>
> or maybe the relations you need to express don''t quite map to
those
> things activerecord makes easy. It''s a case by case thing, much as
I''d
> far write the above than write the equivalent sql, I wouldn''t
waste
> time trying to force activerecord through hoops when it was clear that
> it wasn''t time well spent.
>
> Fred
> > I need to calculate for example taxable income via a query going
> > across 5 tables.  Some like this: Find all transaction records
> > (transactions table), for which they are allocated (via allocation
> > table) to person X (person table), for transaction dates within
> > date1 & date2, for which the category (categories table)
associated
> > with transaction, has a tax_id (from tax_codes table) of XYZ.  I
> > will need to reuse this type of query as I build a report of various
> > tax categories.
> >
> > Question - What would Rails best practice way for the above?
> >
> > [I''m thinking best to create a flat view of this and use this
to
> > then query against]
> >
> > Thanks