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vvvvalvalval / datomic_datalog_count-related-entities-with-zero-sums.clj

Last active November 7, 2024 08:51

Datomic datalog: counting related entities with 0 sums

	;; Imagine you have Persons and Dogs entities in you database, with a :dog/master relationship from Dogs to Persons

	;; you want a report of how many dog each person in you database has, as a set of [<person-name> <number-of-dogs>], e.g:

	#{["John Doe" 3]
	["Foo bar" 0]
	["Chuck Norris" 1]}

	;; in particular, you want person who do not have a dog to appear in this report.