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datalog: aggregation count/sum/min/max (Phase 8, 134/134)
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New lib/datalog/aggregates.sx: (count R V Goal), (sum R V Goal),
(min R V Goal), (max R V Goal). dl-eval-aggregate runs
dl-find-bindings on the goal under the outer subst, collects
distinct values of V, applies the operator, binds R. Empty input:
count/sum return 0; min/max produce no binding (rule fails).

Group-by emerges naturally from outer-subst substitution into the
goal — `popular(P) :- post(P), count(N, U, liked(U, P)), >=(N, 3).`
counts per-post.

Stratifier extended: dl-aggregate-dep-edge contributes a
negation-like edge so the aggregate's goal relation is fully
derived before the aggregate fires (non-monotonicity respected).
Safety relaxed for aggregates: goal-internal vars are existentials,
only the result var becomes bound.
This commit is contained in:
giles
2026-05-08 08:28:45 +00:00
parent caec05eb27
commit 6d04cf7bf2
9 changed files with 447 additions and 27 deletions
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43
lib/datalog/strata.sx
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@@ -33,22 +33,30 @@
(for-each
(fn
(lit)
(let
((target
(cond
((and (dict? lit) (has-key? lit :neg))
(dl-rel-name (get lit :neg)))
((dl-builtin? lit) nil)
((and (list? lit) (> (len lit) 0))
(dl-rel-name lit))
(else nil)))
(neg?
(and (dict? lit) (has-key? lit :neg))))
(when
(not (nil? target))
(append!
existing
{:rel target :neg neg?}))))
(cond
((dl-aggregate? lit)
(let
((edge (dl-aggregate-dep-edge lit)))
(when
(not (nil? edge))
(append! existing edge))))
(else
(let
((target
(cond
((and (dict? lit) (has-key? lit :neg))
(dl-rel-name (get lit :neg)))
((dl-builtin? lit) nil)
((and (list? lit) (> (len lit) 0))
(dl-rel-name lit))
(else nil)))
(neg?
(and (dict? lit) (has-key? lit :neg))))
(when
(not (nil? target))
(append!
existing
{:rel target :neg neg?}))))))
(get rule :body)))))))
(dl-rules db))
g))))
@@ -79,6 +87,9 @@
(let
((t
(cond
((dl-aggregate? lit)
(let ((edge (dl-aggregate-dep-edge lit)))
(if (nil? edge) nil (get edge :rel))))
((and (dict? lit) (has-key? lit :neg))
(dl-rel-name (get lit :neg)))
((dl-builtin? lit) nil)