On Feb 14, 12:43 am, Chris <[email protected]> wrote:
> Hi all,
>
> I'd really appreciate any help / advice on this problem. When I test
> this
>
> def edit
> @entity = Entity.find(params[:id],
> :include => :key_factors)
> @traits = Trait.find :all,
> :include => :trait_values,
> :joins => :trait_values,
> :joins => "LEFT OUTER JOIN key_factors ON
> key_factors.trait_value_id = trait_values.id AND
> key_factors.entity_id="[email protected]_s,
> :order => 'traits.ordering, traits.name'
> @frequencies = Frequency.find :all,
> :order => 'value'
> end
>
> I get the error "ActiveRecord::StatementInvalid: Mysql::Error: Unknown
> column 'trait_values.id' in 'on clause': SELECT `traits`.* FROM
> `traits` LEFT OUTER JOIN key_factors ON key_factors.trait_value_id =
> trait_values.id AND key_factors.entity_id=953125641". I would have
> thought that since I'm including trait_values then that table would be
> in the SQL statement. However, what I see in the development log is:
>
> [4;36 Entity Load (0.0ms) SELECT * FROM `entities` WHERE
> (`entities`.`id` = 1)
> [4;35 KeyFactor Load (0.0ms) SELECT `key_factors`.* FROM
> `key_factors` WHERE (`key_factors`.entity_id = 1)
> [4;36 Trait Load (0.0ms)Mysql::Error: Unknown column
> 'trait_values.id' in 'on clause': SELECT `traits`.* FROM `traits` LEFT
> OUTER JOIN key_factors ON key_factors.trait_value_id = trait_values.id
> AND key_factors.entity_id=1 ORDER BY traits.ordering, traits.name
>
> Which suggests that Rails is doing a separate call for each include...
> and a bit of research on the API confirms that. However, in an earlier
> version of rails this worked fine - the log for running the exact same
> code shows (more or less - replaced a long field list with '*' to make
> reading easier)
Yup that is what happens. It should fall back to the old code in cases
like this however I suspect that it doesn't check the :joins clause
for tables for that need to be included in the old way.
I'm assuming you do actually want that include (and that it wasn't
just an easy way of triggering a join) since the answer is probably a
lot easier if you don't need the include.
Rails will fall back to the old code whenever it sees something that
looks like you're using a table that isn't the base table or provided
through the joins clause. As I said, unfortunately I don't think it
checks the join clause in this way for references to tables.
You should be able fix it by adding a dud condition that references
the included table. I suspect it was just you poking around but doing
:joins => :trait_values,
:joins => "LEFT OUTER JOIN key_factors ON ... "
doesn't do anything since a hash can only have one value for a given
key.
YOu could also try
:joins => "INNER JOIN trait_values ON ... LEFT OUTER JOIN key_factors
ON ... "
This would allow the query to run ok, however I suspect it would still
process the include off the back of a second query.
Fred
>
> [4;36 Trait Load Including Associations (0.000000) SELECT * FROM
> traits LEFT OUTER JOIN trait_values ON trait_values.trait_id =
> traits.id LEFT OUTER JOIN key_factors ON key_factors.trait_value_id =
> trait_values.id AND key_factors.entity_id=1 ORDER BY traits.ordering,
> traits.name
>
> My models are:
>
> class Trait < ActiveRecord::Base
> has_many :trait_values, :dependent => :destroy
> end
>
> class TraitValue < ActiveRecord::Base
> belongs_to :trait
> has_many :key_factors, :dependent => :destroy
> has_many :trait_value_images, :foreign_key =>
> 'related_id', :dependent => :destroy
>
> def sorter
> [(self.trait.ordering || "0"),(self.trait.name || "0"),
> (self.ordering || "0"),(self.name || "")]
> end
>
> end
>
> The API suggests that having conditions on a has_many association
> might do the trick, but the condition would be to be able to be
> dynamically specified ("...key_factors.entity_id="[email protected]_s)
> and I don't see how that's possible when defining the condition on the
> association in the model (not sure whether that's because it actually
> isn't possible or just because I don't know Rails well enough).
>
> Please help!
>
> -Chris Warren
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