I believe it cant be inferred, thats why:
Order.where(:items => {:name => "X"})
SELECT `orders`.* FROM `orders` WHERE `orders`.`name` = 'X' <== Clearly
wrong.
Order.*includes(:item)*.where(:items => {:name => "X"})
SELECT `orders`.`id` AS t0_r0, `orders`.`item_id` AS t0_r1, ... ,
`items`.`id` AS t1_r0, `items`.`name` AS t1_r1, ... FROM `orders` LEFT
OUTER JOIN `items` ON `items`.`id` = `orders`.`item_id` WHERE
`orders`.`name` = 'X'
Selects every column from Order and Item using *LEFT OUTER JOIN**
*Order.*joins(:item)*.where(:items => {:name => "X"})
SELECT `orders`.* FROM `orders` INNER JOIN `items` ON `items`.`id` =
`orders`.`item_id` WHERE `items`.`name` = 'X'
*INNER JOIN*s selection without selecting every field*
*Order.*includes(:item).joins(:item)*.where(:items => {:name => "X"})
SELECT `orders`.`id` AS t0_r0, `orders`.`item_id` AS t0_r1, ... ,
`items`.`id` AS t1_r0, `items`.`name` AS t1_r1, ... FROM `orders` INNER
JOIN `trackers` ON `trackers`.`id` = `issues`.`tracker_id` WHERE
`trackers`.`name` = 'X'
*INNER JOIN*s selection *selecting* every field
Each options have its own behaviour, and is suitable for one case.
Everton
On Sat, Sep 1, 2012 at 11:03 AM, Matt Jones <[email protected]> wrote:
>
> On Aug 31, 2012, at 4:56 PM, Matt Jones wrote:
>
> >
> > On Aug 31, 2012, at 4:08 PM, zdennis wrote:
> >
> >> In the following snippet, can't the includes being inferred from the
> where clause?
> >>
> >> Order.includes(:items).where(:items => { :category => [1,2,3] })
> >>
> >> Can't the includes be inferred from the where clause?
> >>
> >> Order.where(:items => { :category => [1,2,3] })
> >>
> >> Would this conflict with any existing usages of the where clause and
> hashes?
> >>
> >
> > The hazard with auto-inferring here (IMHO) is that it makes forgetting a
> joins clause go from a runtime error to a silent logic error. If I *meant*
> to build this chain:
> >
> > Order.joins(:items).where(:items => { :category => [1,2,3] })
> >
> > but forgot the joins, I've now got a query that returns *all* Orders.
> Not a big deal in this case, but could be a recipe for disaster if the
> conditions in the where are for access control...
>
> Ugh, posting before testing - this actually only happens if you have a
> condition in the where that evaluates to true for NULLs. I still think the
> overall criticism stands, however.
>
> --Matt Jones
>
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Everton
http://www.evertonmoreth.com.br
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