Jeremy,
Thanks so much for your quick reply, the add_graph_aliases function does
exactly what I need!
Regards,
Bert Spaan
On Thursday, February 14, 2013 5:15:40 PM UTC+1, Jeremy Evans wrote:
>
> On Thursday, February 14, 2013 5:03:36 AM UTC-8, Bert Spaan wrote:
>>
>> Hi all,
>>
>> I use Sequel to model two tables using a one_to_many association:
>>
>> class Node < Sequel::Model
>> one_to_many :node_data
>> end
>>
>> class NodeDatum < Sequel::Model
>> many_to_one :node
>> end
>>
>>
>> And I get data from the DB using the following Sequel call:
>>
>> results = Node.where(:name=>name)
>> .eager_graph(:node_data)
>> .order(:id).all.map { |a|
>> a.values.merge(:node_data=>a.node_data.map{|al| al.values}) }
>>
>>
>> Also, next to the default columns from the nodes table, I need an extra
>> column computed by a DB function:
>>
>> Node.select_append(Sequel.function(:collect_member_geometries, :members))
>>
>>
>> However, I need the extra column and function call together with the
>> eager_graph join, but when I try to do this, the extra column seems to
>> get lost after the join.
>>
>> results = Node.where(:name=>name)
>> .eager_graph(:node_data)
>> .select_append(Sequel.function(:collect_member_geometries, :members))
>> .order(:id).all.map { |a|
>> a.values.merge(:node_data=>a.node_data.map{|al| al.values}) }
>>
>>
>> Now the extra column (outcome of collect_member_geometries DB function)
>> is not to be found in results.
>>
>> Does anyone know what I am doing wrong or what I should change to make
>> this work?
>>
>>
> You cannot use select_append when using eager_graph. You need to use
> add_graph_aliases so that Sequel knows in which object to put the columns:
>
> results = Node.where(:name=>name)
> .eager_graph(:node_data)
> .add_graph_aliases(:member_geometries=>[:nodes, :member_geometries,
> Sequel.function(:collect_member_geometries, :members)])
> .order(:id).all.map { |a|
> a.values.merge(:node_data=>a.node_data.map{|al| al.values}) }
>
>
> Also, just FYI, it's a good idea to always make sure that non-identifier
> expressions in the SELECT clause have explicit aliases when using Sequel.
> This is usually necessary when writing portable code (as different
> databases vary in the default alias names they use), but even if you are
> targetting a single database, if the default alias name chosen by the
> database varies with the input data, it's possible to open yourself up to a
> DoS attack (as Sequel converts the alias names returned by the database to
> symbols). Note that the code you posted is not vulnerable to such an
> issue, but it's still a good idea to alias the function call:
>
> .select_append(Sequel.function(:collect_member_geometries,
> :members).as(:some_alias))
>
> Thanks,
> Jeremy
>
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