queries.md

Return maps

return-map  = (return-keys | return-syms | return-strs)
return-keys = ':keys' symbol+
return-syms = ':syms' symbol+
return-strs = ':strs' symbol+

If you need a query to return a set of maps instead set of tuples, specify one of :keys / :syms / :strs, followed by a list of symbols:

[:find ?name ?age ?email, ...]
=> #{["Ivan" 10 "ivan@"]
     ["Oleg" 20 "oleg@"]
     ["Sergey" 30 "sergey@"]}

[:find ?name ?age ?email
 :keys name A e-mail
 ...]
=> #{{:name "Ivan",   :A 10, :e-mail "ivan@"}
     {:name "Oleg",   :A 20, :e-mail "oleg@"}
     {:name "Sergey", :A 30, :e-mail "sergey@"}}

:strs forces map to have string keys, :syms for symbols.

Return maps are only compatible with normal find and tuple-returning find:

[:find [?name ?age ?email], ...]
=> {:name "Ivan",   :A 10, :e-mail "ivan@"}

The amount of keys must match the amount of find elements.

Datomic docs: https://docs.datomic.com/query/query-data-reference.html#return-maps

Query functions

tuple

[(tuple ?a ...) ?tup]

Given one or more values, the tuple function returns a tuple containing each value. See also untuple.

;; query
[:find ?tup
 :in ?a ?b
 :where [(tuple ?a ?b) ?tup]]

;; inputs
1 2

;; result
#{[[1 2]]}

untuple

[(untuple ?tup) [?a ?b]]

Given a tuple, the untuple function can be used to name each element of the tuple. See also tuple.

;; query
[:find ?b
 :in ?tup
 :where [(untuple ?tup) [?a ?b]]]

;; inputs
[1 2]

;; result
#{[2]}