Sync: a flag set on the server left the thread counters stale

Reported from the running app: a message showed as unread in the list — bold, blue dot — while the reading pane showed it as read, and only a manual "mark as read" reconciled them. The two views read different things. The pane reads the message's own flags; the list reads `threads.unread_count`, denormalized from them. `apply_delta` updated message flags with a bare UPDATE and never recomputed the thread, so a flag set anywhere but in this app — read on a phone, filed by a server-side rule — moved one and not the other. Auto-mark-on-read could not fix it either: it sees a message that is already \Seen and correctly does nothing, leaving the counter wrong forever. Expunges had the same hole, which also left `message_count` overstated. `apply_delta` now collects the affected threads and re-denormalizes them after the deletes, so a thread emptied by an expunge is removed rather than recounted. Migration 0018 repairs rows that already drifted — recomputed from the messages, so it is a no-op on a healthy database. One thread was stale here; installs that have been syncing longer will have more. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_018SqJYt7jD7oUEkoY68sBZo
2026-09-18 18:21:30 +02:00
parent de79b4ba07
commit e58a2f0ef4
3 changed files with 163 additions and 6 deletions
@@ -0,0 +1,55 @@
+"""repair thread counters left stale by server-side flag changes and expunges
+
+`threads.unread_count`, `pinned` and `message_count` are denormalized from the
+thread's messages. Two sync paths updated messages without recomputing them: a
+flag change reported by the server (mail read on a phone, or filed by a
+server-side rule) and a QRESYNC expunge. The row then disagreed with its own
+messages — the message list showing a message as unread that the reading pane
+showed as read, and only a manual "mark as read" reconciling it.
+
+The code paths are fixed; this repairs rows that already drifted. Recomputes from
+the messages themselves, so it is safe to run on a healthy database: threads that
+already agree are left untouched.
+
+Revision ID: 0018
+Revises: 0017
+Create Date: 2026-09-18
+"""
+
+from __future__ import annotations
+
+from collections.abc import Sequence
+
+from alembic import op
+
+revision: str = "0018"
+down_revision: str | None = "0017"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    op.execute(
+        r"""
+        UPDATE threads t
+           SET unread_count  = s.unread,
+            pinned        = s.pinned,
+            message_count = s.total
+        FROM (
+            SELECT thread_id,
+                   count(*)                                        AS total,
+                   count(*) FILTER (WHERE NOT ('\Seen' = ANY(flags)))    AS unread,
+                   bool_or('\Flagged' = ANY(flags))                AS pinned
+            FROM messages
+            WHERE thread_id IS NOT NULL
+            GROUP BY thread_id
+        ) AS s
+        WHERE t.id = s.thread_id
+          AND (t.unread_count, t.pinned, t.message_count) IS DISTINCT FROM
+              (s.unread, s.pinned, s.total)
+        """
+    )
+
+
+def downgrade() -> None:
+    """Nothing to undo: this only makes rows agree with the messages they describe."""