remove_database() closes the Database, which closed every connection in
_all_connections - including a catalog scan connection still in use on a
worker thread: segfault (crashed an xdist worker in the full suite,
reproduced with an add/remove stress loop). Database.connect(track=False)
leaves the watcher's short-lived connections to the watcher, which always
closes them on the thread that opened them. Regression test added.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwkLo2rJWidpkDVT3HkvNv
When the fingerprint shows no non-empty -wal or -journal the main file is
the whole database, so the sweep reads the schema cookie (offset 40 of
the header) with pread instead of opening a connection. No SHARED lock
means no busy back-off for a concurrent writer: polling was costing
write-heavy phases ~10% throughput and up to 2x p99. The fingerprint is
still taken first, so a commit in flight is covered by the racy rule.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwkLo2rJWidpkDVT3HkvNv
- write connections reopened after the watcher saw the file replaced or
deleted use mode=rw, so a write to a deleted database fails instead of
silently creating a new empty file
- derived_table_dependencies() keys its cache on the schema_version the
watcher stored in the catalog (plus its scan count) instead of running
PRAGMA schema_version on a pooled read connection - allowed_resources()
calls it for every database on every page
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwkLo2rJWidpkDVT3HkvNv
Per-database schema_watch modes (owned / external / immutable):
- write path reads PRAGMA schema_version after every write task and
rebuilds that one database's catalog before the write returns
- external files are polled with a stat() fingerprint prefilter
(racily-clean fingerprints re-verified), PRAGMA schema_version only on
change, rebuild only when the version moved or the inode changed
- immutable databases are scanned once
- remove_database deletes its catalog rows explicitly; startup deletes
rows for databases that are not attached (no per-refresh full scans)
- catalog reads use one short-lived connection per database inside one
read transaction; shared-cache memory databases go through their
write thread
- replaced/deleted files invalidate cached connections (generation)
- fingerprints persisted in catalog_databases.fingerprint (migration
0002) so restarts skip unchanged files
- new setting schema_watch_interval_ms (default 1000, 0 = no polling)
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwkLo2rJWidpkDVT3HkvNv
