datalog: bipartite friends-with-hobby join test (229/229)

lib/datalog/scoreboard.json

@@ -1,13 +1,13 @@
 {
   "lang": "datalog",
-  "total_passed": 228,
+  "total_passed": 229,
   "total_failed": 0,
-  "total": 228,
+  "total": 229,
   "suites": [
     {"name":"tokenize","passed":26,"failed":0,"total":26},
     {"name":"parse","passed":18,"failed":0,"total":18},
     {"name":"unify","passed":28,"failed":0,"total":28},
-    {"name":"eval","passed":30,"failed":0,"total":30},
+    {"name":"eval","passed":31,"failed":0,"total":31},
     {"name":"builtins","passed":20,"failed":0,"total":20},
     {"name":"semi_naive","passed":8,"failed":0,"total":8},
     {"name":"negation","passed":10,"failed":0,"total":10},
@@ -16,5 +16,5 @@
     {"name":"magic","passed":28,"failed":0,"total":28},
     {"name":"demo","passed":21,"failed":0,"total":21}
   ],
-  "generated": "2026-05-08T12:35:21+00:00"
+  "generated": "2026-05-08T12:38:51+00:00"
 }

lib/datalog/scoreboard.md

@@ -1,13 +1,13 @@
 # datalog scoreboard
 
-**228 / 228 passing** (0 failure(s)).
+**229 / 229 passing** (0 failure(s)).
 
 | Suite | Passed | Total | Status |
 |-------|--------|-------|--------|
 | tokenize | 26 | 26 | ok |
 | parse | 18 | 18 | ok |
 | unify | 28 | 28 | ok |
-| eval | 30 | 30 | ok |
+| eval | 31 | 31 | ok |
 | builtins | 20 | 20 | ok |
 | semi_naive | 8 | 8 | ok |
 | negation | 10 | 10 | ok |

lib/datalog/tests/eval.sx

@@ -273,6 +273,18 @@
           (dl-saturated? db))
         false)
 
+      ;; Bipartite-style join: pair-of-friends who share a hobby.
+      ;; Three-relation join exercising the planner's join order.
+      (dl-et-test-set! "bipartite friends-with-hobby"
+        (dl-query
+          (dl-program
+            "hobby(alice, climb). hobby(bob, paint).
+             hobby(carol, climb).
+             friend(alice, carol). friend(bob, alice).
+             match(A, B, H) :- friend(A, B), hobby(A, H), hobby(B, H).")
+          (list (quote match) (quote A) (quote B) (quote H)))
+        (list {:A (quote alice) :B (quote carol) :H (quote climb)}))
+
       ;; Repeated variable (diagonal): p(X, X) only matches tuples
       ;; whose two args are equal. The unifier handles this via the
       ;; subst chain — first occurrence binds X, second occurrence