It is currently not possible to use aggregations within rules, because they can only appear within the find specification. It should be possible to use aggregations like transforms:
[[(total ?user ?sum)
[?user :user/purchase ?purchase]
[?purchase :purchase/amount ?amount]
[(sum ?amount) ?sum]]]
It is currently not possible to use aggregations within rules, because they can only appear within the find specification. It should be possible to use aggregations like transforms: