[query] Allow to bind `[(min ?t) ?t0]` #270

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opened 2020-08-06 16:57:39 +00:00 by gburd · 0 comments

gburd commented

2020-08-06 16:57:39 +00:00

(Migrated from github.com)

Mentat allows to order results; Datomic does not. When expressing "least or greatest in a group" style queries, the fact that we can't manipulate the max or min outside of the find spec is limiting. That is, it's not easy to ask for "the 10 most recently used items" or whatever.

I think we might be able to bind scalars to achieve this. That is, we might find that

:find
 [?e ...]
:where
 [?e :value ?v]
 [(min ?v) ?v0]
:order
 (desc ?v0)
:limit
 10

is generally useful.

Mentat allows to order results; Datomic does not. When expressing "least or greatest in a group" style queries, the fact that we can't manipulate the `max` or `min` outside of the find spec is limiting. That is, it's not easy to ask for "the 10 most recently used items" or whatever. I think we might be able to bind scalars to achieve this. That is, we might find that ``` :find [?e ...] :where [?e :value ?v] [(min ?v) ?v0] :order (desc ?v0) :limit 10 ``` is generally useful.