So I get the impression that non-additive changes to the schema are tricky. Is creating a new DB and re-importing data the only way to fundamentally alter the schema?

And is this feasible to do?

I'm just worried that if our requirements change down the road in a way we did not anticipate, are we stuck?

@currentoor: it depends on what you need to change. Supported schema alteration is documented here: http://docs.datomic.com/schema.html#Schema-Alteration

Right so when they say "You cannot alter :db/valueType or :db/fulltext." Can I work around that with a re-import?

if absolutely necessary?

Or would that not work?

@currentoor: I think it would work but in the case of a valueType change you'd need to convert all relevant datoms in each tx during import from old type to new type.

I see.

Makes sense.

is there a way to specify the transactor’s host via environment variables, rather than in the config file?

@currentoor: you can also use renaming. :old-typeA. make :new-typeB, transact all the values (while converting types) from :old to :new, and then rename :old to :old-unused and :new to :old.

disadvantage: you lose all your transaction time history, but then you would anyway if you recreated your db without re transacting everything in time order

hi guys what is part in db.part in datomic ?

why [(= (f ?var-1) (f ?var-2))] is invalid?

I know there is a equivalent way: [(f ?var-1) ?value] [(f ?var-2) ?value]

@nxqd: http://docs.datomic.com/schema.html#partitions

@isaac: you can’t nest function calls in datalog. if you need to, you should defer to a namespaced function instead

@robert-stuttaford: thanks

@robert-stuttaford: Is that means nested function not supported? or I need use namespaced function?

@isaac: not supported. must use namespaced function

both?

nested function calls are not supported. you must use a namespaced function call instead. no: [(= (f ?x) (f ?y)] yes: [(my.ns/is-=-with-f? ?x ?y)]

got it, now?

@robert-stuttaford: I got it ,thank you

@isaac: there’s also an example stepped out (rather than writing a custom function and calling it with namespaced example) here: http://stackoverflow.com/questions/32164131/parameterized-and-case-insensitive-query-in-datalog-datomic/32323123#32323123 So i.e.: [ (re-find (re-pattern (str "(?i)" ?par)) ?bfn)] Becomes:

[(str "(?i)" ?match) ?matcher]
[(re-pattern ?matcher) ?regex]
[(re-find ?regex ?aname)]

@bkamphaus: that good, thanks

I am wondering if it is possible to make a sort of custom as-of function. I am marking my transactions with a “transaction time” or :db/tt instant, which is different (and before) :db/txInstant (which is when the data was received in my use case), and I want to be able to query datoms that have :db/tt that are before a certain time.

Is that at all possible?

Hi. How do I get last Datomic version?

UPD: Found this: https://my.datomic.com/downloads/pro Last one must be on the top of the list

@casperc: Sure, why not just write a function to find the tx with the correct :db/tt and then use as-of with that tx's id?

@domkm: I thought about that, but I need the as-of to operate on the :db/tt value, not :db/txInstant

I think that filter might be a workable solution though, so I am taking a look at that

as-of takes a t, tx, or inst

just give it the tx id of the tx with the desired :db/tt

@domkm: I don’t need the database as-of the txInstant of some :db/tt, I need all datoms with :db/tt bigger than some date. There is a difference in my use case

Oh

Yeah, then filter

Don’t know how it performs though, but I guess I will find out

Heh, yup

@casperc: index-range might also be useful for you

@domkm: I was looking at that too, but I don’t quite see how it can help me, unfortunately

I'm benchmarking a query (a big pull of a few hundred entities) both as a peer and via the REST API. To my great surprise, querying via the REST API is consistently faster. Can I believe this result? Does the REST server do some clever caching of serialized results or something?