On Wednesday, April 27, 2016 at 7:55:23 AM UTC+2, The Bang Nguyen wrote:
>
> Hi all,
>
> I have 2 models let's say `Model` and `Event`.
> `Model` has `one_to_many` association to `Event`.
>
> `Event` has column `event_type` which indicates the event happened on a
> `Model`.
> `event_type` could be `do_something` or `undo_something` or
> `some_others_action`.
>
> I would like to return a `dataset` in which:
> - if there is no `do_something` or `undo_something` event
> -- return all columns in `Model` plus `did_something` column as
> `false`.
> - if there is `do_something` and no `undo_something` event
> -- return all columns in `Model` plus `did_something` column as
> `true`.
> - if there is `do_something` and `undo_something` event. And
> `created_time` of last `do_something` is greater than `created_time` of
> last `undo_something`
> -- return all columns in `Model` plus `did_something` column as
> `true`.
> - if there is `do_something` and `undo_something` event. And
> `created_time` of last `do_something` is less than `created_time` of last
> `undo_something`
> -- return all columns in `Model` plus `did_something` column as
> `false`.
>
I think something like this may work (completely untested):
Model.dataset_module do
def with_did_something
event_ds = join(:events, :model_id=>:id)
do_something =
event_ds.where(:event_type=>'do_something').max(:created_time)
undo_something =
event_ds.where(:event_type=>'undo_something').max(:created_time)
did_something = do_something && (!undo_something || undo_something <
do_something)
ds = select_all(:model_table).select_append(Sequel.as(did_something,
:did_something))
end
end
Thanks,
Jeremy
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