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#datomic
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2016-02-15
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jimmy03:02:57

@val_waeselynck, @bkamphaus thanks for helping. i have done the same thing, I do sorting by using sort-by and paging by partition and take

jimmy04:02:20

hi guys, can't we use a rule like this in datomic : [[(rule-name rule-arg) [(not (< rule-arg 0.5))]]

bkamphaus04:02:18

@nxqd: this looks like a similar case to what was raised here: http://stackoverflow.com/questions/32164131/parameterized-and-case-insensitive-query-in-datalog-datomic — function expressions in datalog don’t nest.

jimmy04:02:26

@bkamphaus: yeah it seems so. I think I will try to solve the problem on the returned data instead of from datalog for now.

bkamphaus04:02:47

@nxqd: sorry, may have read too quickly. You should be able to make rules using negation and disjunction, though I haven’t put together a rule like that any time recently that I remember. Of course, in the example you provide, you can negate < with >=

jimmy04:02:16

@bkamphaus: I'm not sure If I remember correctly or not that we cannot apply nested clauses in datomic ? just make sure I understand things correctly

bkamphaus04:02:42

you can’t nest function calls. not, not-join, or, and or-join, though specify negation and disjunction which apply to the clauses that follow them, which is a different case. They have an inside/outside e.g. not vs. the default and-like behavior in datalog.

val_waeselynck15:02:31

@bkamphaus: is it safe to use db.with() on a memory database value after the mem connection which created was released or deleted ?

bkamphaus16:02:16

@val_waeselynck: that’s definitely on the edges of my knowledge — have you already encountered issues doing this or are you checking prior to attempting? I’ll have to look into it, just helpful to know context of my doing so beforehand.

val_waeselynck16:02:06

I had an issue where my auto-reloaded tests would complain about a database having been released, but haven't been able to reproduce

val_waeselynck16:02:22

so mostly checking prior to attempting

val_waeselynck16:02:55

let me rephrase it: it's worked for me so far, but maybe it's only because I have been lucky

bplatz18:02:00

Does Datomic provide any access to its' transaction expansion? I want to fully expand a transaction (tx functions, tx maps) into the final tx that the transactor will invoke (`[ [:db/add :e :a :v :tx] ...]`) so I can do some pre-validation work before allowing a transaction to go through.

bplatz18:02:55

I suppose I could try to cram all conceivable logic into a db transaction, but I'm trying to keep it out of there.

bplatz18:02:26

I don't need the real-time tx, just what it would be if executed at that point in time... that is enough for me to do my pre-work.

bkamphaus18:02:06

@bplatz: not at present. It is a feature that’s been requested and I can note your interest in it. https://groups.google.com/forum/#!searchin/datomic/transaction$20map$20form/datomic/9D6zZYkiGlw/hc06dtalyS0J — it is a fairly simple transform as noted here: http://docs.datomic.com/transactions.html#map-forms — "Each attribute, value pair becomes a :db/add list using the entity-id value associated with the :db/id key."

bplatz18:02:36

Tx functions are the ones I'm more concerned about. Nested entities/refs as well, but those aren't too bad.

bkamphaus18:02:55

@bplatz: a transaction function called with datomic.api/invoke instead of in a transaction will return its transaction data (rather than transacting it).

bplatz18:02:33

so... assuming I have [[:db.fn/retractEntity [:person/email ""]]], I'd look at the tx for two-element vectors, then call (d/invoke db (first v) (second v))? And I assume I'd do that in first-to-last order of the transaction, assuming I need to do that for multiple functions?

bplatz18:02:21

I guess it is like macro-expansion... so probably each function invocation I start the parse over from scratch.

bplatz19:02:23

And I'm just trying to be specific to make sure I replicate what Datomic does internally, else it doesn't achieve the goal. Thanks.

bplatz19:02:39

Actually just realized there can be multiple params passed to a function, so scratch the first/second comment. So just wrapping up my logic, the order I'll look to implement is (1) expand all maps with :db/add, (2) look for any tx function (where first vector element is not :db/add or :db/retract) and use (d/invoke db ...). (3) repeat step 2 to look for more functions, stop when no addition functions are found.

casperc20:02:35

What is the best way to implement a limit or paging functionality in Datomic?

casperc20:02:04

I guess just doing paging an a query doing a (pull ) is a bad idea since it is pulling a bunch of data up front, so should I find the entities, filter/page and then pull?

val_waeselynck20:02:15

@casperc yes I usually run a query to find the entities ids Im interested in, then convrt them to entities, sort, paginate, then map a function which converts them to maps (or whatever format the client needs)

casperc20:02:56

@val_waeselynck: so you use the d/entity function to get the entity before paginating? Is that fast enough?

val_waeselynck22:02:24

well as we all know i cant disclose any benchmark :) but this approach has worked for me so far. I dont believe entities have a lot of overhead since theyre lazy and whatever segment they live in has been loaded in the previous query

meow23:02:12

Why can't benchmarks be disclosed