db gains :facts-index {<rel>: {<first-arg-key>: tuples}} mirroring
the membership :facts-keys index. dl-add-fact! populates the index;
dl-match-positive walks the body literal's first arg under the
current subst — when it's bound to a non-var, look up by (str arg)
instead of scanning the full relation.
For chain-style recursive rules (parent X Y), (ancestor Y Z) the
inner Y has at most one parent, so the inner lookup returns 0–1
tuples instead of N. chain-25 saturation drops from ~33s to ~18s
real (~2x). chain-50 still long but tractable; next bottleneck is
subst dict copies during unification.
dl-retract! refreshed to keep the new index consistent: kept-index
rebuilt during EDB filter, IDB wipes clear all three slots.
Differential semi-naive test bumped to chain-12, semi-only count
test to chain-25.
dl-query now auto-dispatches on the first element's shape:
- positive literal (head is a symbol) or {:neg ...} dict → wrap
- list of literals → conjunctive query
dl-query-coerce normalizes; dl-query-user-vars collects the union
of user-named vars (deduped, '_' filtered) for projection. Old
single-literal callers unchanged.
(dl-query db '(p X)) ; single
(dl-query db '((p X) (q X))) ; conjunction
(dl-query db (list '(n X) '(> X 2))) ; with comparison
2 new api tests cover multi-goal AND and conjunction with comparison.
(p X _), (p _ Y) — the two _ are now different variables, matching
standard Datalog semantics. Previously both _ symbols were the same
SX symbol, so unification across them gave wrong answers.
Fix in db.sx: dl-rename-anon-term + dl-rename-anon-lit walk a term
or literal and replace each '_' symbol with a fresh _anon<N>.
dl-make-anon-renamer returns a counter-based name generator scoped
per call. dl-rename-anon-rule applies it to head and body of a
rule. dl-add-rule! invokes the renamer before safety check.
eval.sx: dl-query renames anon vars in the goal before search and
filters '_' out of the projection so user-facing results aren't
polluted with internal _anon<N> bindings.
The previous "underscore in head ok" test now correctly rejects
(p X _) :- q(X) as unsafe (the head's fresh anon var has no body
binder). New "underscore in body only" test confirms the safe
case. Two regression tests for rule-level and goal-level
independence.
dl-find-bindings now uses dl-fb-aux lits db subst i n (indexed
iteration via nth) instead of recursive (rest lits). Eliminates
O(N²) list-copy per body of length N. chain-15 saturation 25s
→ 16s; chain-25 finishes in 33s real (vs. timeout previously).
Bumped semi_naive tests to chain-10 differential + chain-15
semi-only count (was chain-5/chain-5). Blocker entry refreshed.
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.
New lib/datalog/strata.sx: dl-build-dep-graph (relation -> deps with
:neg flag), Floyd-Warshall reachability, SCC-via-mutual-reach for
non-stratifiability detection, iterative dl-compute-strata, and
dl-group-rules-by-stratum.
eval.sx refactor:
- dl-saturate-rules! db rules — semi-naive worker over a rule subset
- dl-saturate! db — stratified driver. Rejects non-stratifiable
programs at saturation time, then iterates strata in order
- dl-match-negation — succeeds iff inner positive match is empty
Order-aware safety in dl-rule-check-safety (Phase 4) already
required negation vars to be bound by a prior positive literal.
Stratum dict keys are strings (SX dicts don't accept ints).
Phase 6 magic sets deferred — opt-in path, semi-naive default
suffices for current workloads.
dl-saturate! is now semi-naive: tracks a per-relation delta dict,
and on each iteration walks every positive body-literal position,
substituting the delta of its relation while joining the rest
against the previous-iteration DB. Candidates are collected before
mutating the DB so the "full" sides see a consistent snapshot.
Rules with no positive body literal (e.g. (p X) :- (= X 5).)
fall back to a one-shot naive pass via dl-collect-rule-candidates.
dl-saturate-naive! retained as the reference implementation; 8
differential tests compare per-relation tuple counts on every
recursive program. Switched dl-tuple-member? to indexed iteration
instead of recursive rest (eliminates per-step list copy). Larger
chains under bundled conformance trip O(n) membership × CPU
sharing — added a Blocker to swap relations to hash-set membership.
New lib/datalog/builtins.sx: (< <= > >= = !=) and (is X expr) with
+ - * /. dl-eval-arith recursively evaluates nested compounds.
Safety analysis now walks body left-to-right tracking the bound
set: comparisons require all args bound, is RHS vars must be bound
(LHS becomes bound), = special-cases the var/non-var combos.
db.sx keeps the simple safety check as a forward-reference
fallback; builtins.sx redefines dl-rule-check-safety to the
comprehensive version. eval.sx dispatches built-ins through
dl-eval-builtin instead of erroring. 19 new tests.
