Datomic insert blocks - schema

Question

The Datomic Seattle examples use explicit ID numbers when doing inserts:
{:db/id #db/id[:db.part/user -1000014], :neighborhood/name "Belltown", :neighborhood/district #db/id[:db.part/user -1000013]}
{:community/category ["community council"], :community/orgtype :community.orgtype/community, :community/type :community.type/website, :db/id #db/id[:db.part/user -1000015], :community/name "All About Belltown", :community/url "http://www.belltown.org/", :community/neighborhood #db/id[:db.part/user -1000014]}
For ordinary inserts for a single schema - it is much simpler to generate the ID on the fly:
[
{
:db/id #db/id[:db.part/user],
:car/model \"Ferrari\"
:car/numberplate \"RENT ME!\"
}
]
and this will generate the ID at the time of insert.
Suppose I have a more complex schema, where I want to represent a Renter, Car and RentEvent.
I could do:
[
{
:db/id #db/id[:db.part/user],
:car/model \"Ferrari\"
:car/numberplate \"RENT ME!\"
}
]
=> get ID number and stick it in A
[
{
:db/id #db/id[:db.part/user],
:renter/name \"John Smith\"
:renter/socialsecuritynumber \"123456789\"
}
]
=> get ID number and stick it in B
[
{
:db/id #db/id[:db.part/user],
:rentevent/car A
:rentevent/renter B
}
]
But that involves lots of mucking around with ID numbers. I'd like to insert this in one big block, something like:
[
{
:db/id #db/id[:db.part/user],
:rentevent/car {
:db/id #db/id[:db.part/user],
:car/model \"Ferrari\"
:car/numberplate \"RENT ME!\"
},
:rentevent/renter {
:db/id #db/id[:db.part/user],
:renter/name \"John Smith\"
:renter/socialsecuritynumber \"123456789\"
}
]
Is this possible? What is the syntax?
Assumptions:
This is an auditable environment where a repeatable scripted database release is done to a production database by an party who is under separation of controls. Ie - this needs to be a text file that an auditor can look at before and after a change to the database is made.

Answer 1

Yes, it's possible. Use a transaction function:
; create a constructor-like function
(def new-rentevent
(d/function '{:lang :clojure
:params [db cm cp rn rs]
:code [{:db/id #db/id[:db.part/user -1]
:car/model cm
:car/numberplate cp}
{:db/id #db/id[:db.part/user -2],
:renter/name rn
:renter/socialsecuritynumber rs}
{:db/id #db/id[:db.part/user]
:rentevent/car #db/id[:db.part/user -1]
:rentevent/renter #db/id[:db.part/user -2]}]}))
; transact the function so it can run inside the transactor
(d/transact conn [{:db/id #db/id[:db.part/user]
:db/ident :new-rentevent
:db/fn new-rentevent}])
; make your application code use the transaction function instead
(d/transact conn [[:new-rentevent "Ferrari" "RENT ME!" "John Smith" "123456789"]])
(d/transact conn [[:new-rentevent "Jaguar" "AVAILABLE" "Kate Nash" "567894345"]])
(d/transact conn [[:new-rentevent "Maserati" "PICK ME!" "Justin Williams" "789134353"]])
For the complete code sample, see this gist. For more info see Database Functions.