Use the :tx-data as a $-database!
The only pitfall is that the second position, the attribute, and all other
references (reference type) is just a reference to the attribute entity (a
long).
Let's say you find :db/txInstant to be 53, and :community/category to be
112 the query would look like
(q '[:find ?tx-eid . in $ :where [?tx-eid 53 _ ?tx-eid true] [_ 112 "free
stuff" ?tx-eid false]] tx-data-as-database)
If this query returns the ?tx-eid, and not nil, the contraints was
fulfilled - test passed.
Given that this is unit testing and performance is probably not a big
issue, maybe it would be possible to write a function generating a datomic
query like the one above, but with conveniences like it automatically
inlines the attribute-entids (or extends the query to automatically looking
them up using some reference to the db with the current schema installed).
Given that Datomic compiles every new query that is not parameterized this
could be quite heavy if it was used in production.
But in short, you can query the tx-data using datalog, the only pitfall is
that datoms are mostly primitives which must be looked up in the datomic db
they came from. I think datoms have a reference to the database they came
from, but I don't know how to use that fact.
It's full of stars.
/Linus
On Wednesday, July 1, 2015 at 9:47:07 PM UTC+2, Alan Thompson wrote:
>
> Hi - I am trying to write some unit tests for Datomic using core.match to
> keep things succinct. I was hoping to use a match pattern like this:
>
> [ {:e tx-eid :a :db/txInstant :v _ :tx tx-eid
> :added true}
> {:e _ :a :community/category :v "free stuff" :tx tx-eid
> :added false} ]
>
> to show that the transaction EID (tx-eid) shows up in 3 places in the
> datoms result of a transaction. However, I am getting the error:
>
> Exception in thread "main" java.lang.AssertionError: Pattern row 1:
> Pattern row reuses wildcards in [[{:e tx-eid, :a :db/txInstant, :v _, :tx
> tx-eid, :added true} {:e _, :a :community/category, :v "free stuff", :tx
> tx-eid, :added false}]]. The following wildcards are ambiguous: tx-eid.
> There's no guarantee that the matched values will be same. Rename the
> occurrences uniquely.,
>
>
> So I am apparently unable to use core.match in the way I was hoping. Are
> there any workarounds to this problem?
>
> Thanks,
> Alan
>
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