Oops, one more.
There was also a Users table (Id, Username, ...)
I didn't see a way to handle join from Races to Users based on SupervisorId
and AnalystId.
On Monday, 29 February 2016 15:52:48 UTC+11, Oliver George wrote:
>
> Thanks for the details.
>
> I did a little experimenting and it works as advertised. Notes below show
> what I did and found.
>
> I was interested to see if this might be suitable as a simple om.next
> remote for a relational database. Potentially fanciful but it's a topic of
> interest for me at the moment.
>
> I used an existing database so I had a semi interesting dataset to play
> with.
>
> Races (Id, RaceNumber, RaceTime, MeetingId, SupervisorId, AnalystId...)
> Meetings (Id, MeetingDate, MeetingTypeId, VenueId, JurisdictionId, ...)
> Venues (Id, Name)
> Jurisdiction (Id, Name, Code)
>
>
> The table and foreign key naming conventions didn't match so I created
> views for each table. If that was configurable then you'd open yourself to
> a wider audience. (e.g. MeetingId vs meetings_id)
>
> It was easy to setup some associations
>
> (def associations
> {:meeting {:race :has-many
> :jurisdiction :belongs-to
> :venue :belongs-to}
> :race {:meeting :belongs-to
> :jurisdiction [:through :meeting :belongs-to]}
> :venue {}})
>
> My queries all worked as expected.
>
> (find-one db-state :meeting #{:race} [[:= :meeting.id 5617]])
> (find-one db-state :meeting #{:venue} [[:= :meeting.id 5617]])
> (find-one db-state :race #{:meeting :jurisdiction} [[:= :race.id 42792]])
>
> I couldn't see how I might pull data which requires three levels of
> information (e.g. race -> meeting -> venue). I didn't dig deep enough to
> be sure.
>
> Incidentally, in case you haven't come across the datomic pull inspired
> om.next remote pull syntax this is what it might look like:
>
> [{:meeting [:race]}]
> (find-one db-state :meeting #{:race} [])
>
> [({:meeting [:race]} [:= :meeting.id 5617])]
> (find-one db-state :meeting #{:race} [[:= :meeting.id 5617]])
>
> [{:meeting [:venue]}]
> (find-one db-state :meeting #{:venue} [[:= :meeting.id 5617]])
>
> [{:race [{:meeting [{:venue :jurisdiction}]}]}]
>
> Not prettier necessarily but allows for composing multiple queries into a
> request and for drilling deeper into available data.
>
> cheers, Oliver
>
>
>
>
>
>
>
> On Sunday, 28 February 2016 20:02:15 UTC+11, Krzysiek Herod wrote:
>>
>> Thanks Oliver for the feedback,
>>
>> actually I came up with the idea of relational_mapper while working on a
>> project in which I had one "data-model" that contained all the database
>> related information, but the database related code contained a lot of
>> features, and I really like working with small, focused clojure libraries,
>> so in the end relational_mapper is as small as I could think of it.
>>
>> Also as you can see in this commit:
>> https://github.com/netizer/relational_mapper/commit/6b4d79f92570bf723e4092d329978d484c01d2ab#diff-2b44df73d826687086fd1972295f8bd0L8
>>
>> I actually was storing both: relations and fields in the same structure,
>> but I changed that because I needed "fields" only for migrations that I
>> used in tests, and because the whole structure was unnecessarily complex
>> (it was much easier to make mistake modifying the fields/associations
>> structure).
>>
>> Relational Mapper is meant only for reading data because whenever I tried
>> to use complex structures to write data, I was unhappy with the result
>> (often you have to update indexes of related records after one of them -
>> with auto-increment field - is created, and there is a problem of
>> determining if the related record has to be created or updated).
>>
>> I didn't write compare/contrast points because I couldn't find similar
>> libraries in clojure. I mentioned ActiveRecord in README mostly because of
>> the wording in types of relations, but even ActiveRecord is very far from
>> Relational Mapper (it's much bigger, and has features that go way beyond
>> simple relational mapping).
>>
>> Thanks again,
>> Krzysiek
>>
>> On Sunday, February 28, 2016 at 10:54:57 AM UTC+8, Oliver George wrote:
>>>
>>>
>>> Seems pretty nice to me. Like a light weight version of the Django's
>>> migrate and queryset features which build on model definitions.
>>>
>>> It seems like this would allow me to define a database schema (tables,
>>> relations and fields) as data and use it to both create the database and
>>> run select/insert/update/delete queries against it.
>>>
>>> Is that your intention for the library?
>>>
>>> I've not explored the options in this space before. It might be good to
>>> have a section in the README pointing out to other related tools with some
>>> compare/contrast points.
>>>
>>> Thanks.
>>>
>>>
>>> On Friday, 26 February 2016 17:51:10 UTC+11, Krzysiek Herod wrote:
>>>>
>>>> I created Relational Mapper, for situations where there is a relational
>>>> database with certain amount of relations between tables and it's just not
>>>> cool to fetch data from each table separately nor to write custom code for
>>>> each such project so, with this library, you can just call:
>>>>
>>>> (find_all db-state :posts #{:authors :attachments} [:= post.id 1])
>>>>
>>>> and assuming you have appropriate relations between these tables, you'll
>>>> get:
>>>>
>>>> {:posts {:title "Christmas"
>>>> :body "Merry Christmas!"
>>>> :id 1
>>>> :authors_id 10
>>>> :authors {:name "Rudolf" :id 10}
>>>> :attachments [{:name "rudolf.png" :id 100 :posts_id 1}
>>>> {:name "santa.png" :id 101 :posts_id 1}]
>>>>
>>>>
>>>> The code is here: https://github.com/netizer/relational_mapper
>>>>
>>>> Please, guys, let me know what do you think, and if you have any ideas
>>>> about improvements. If somebody would be so kind to take a look at the
>>>> code, it would be awesome to read some feedback.
>>>>
>>>> Krzysiek Heród
>>>>
>>>
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