On 22/08/18 22:03, Andy Armstrong wrote:
> On 22 Aug 2018, at 20:55, Matthew Somerville <matt...@mysociety.org> wrote:
>> On 22 August 2018 at 20:22, Andy Armstrong <a...@hexten.net> wrote:
>>> If I do prefetch => ['service', { service => 'parent' }] I only get results 
>>> for the cases where the service hierarchy is two levels deep.
>> I think you might only want prefetch => { service => 'parent' } ?
>> The "The "prefetch" attribute can be used with any of the relationship
>> types" bit of the documentation seems relevant here, it sounds like
>> there's no reason why it wouldn't work, as long as it knows the parent
>> is optional (might_have). Like "liner_notes" in the example.
> That seems to generate a query that limits the results to only those services 
> that have multiple levels - which is understandable.

Sounds like the join type might be wrong for the 'parent' relationship.
You can add:

  join_type => 'LEFT'


> I'm now contemplating whether the services really need to be hierarchical. 
> It's an awkward fit for a single query regardless of whether I use DBIC and 
> only works in the current implementation because the whole services table is 
> loaded once and converted at that point into a shallow tree.

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