Read path: the leased pool replaces the thread-local cache. Pooled
connections record Database._conn_generation when opened; a stale one is
discarded on checkout or return, and _invalidate_connections() (called
by the SchemaWatcher on a replaced/deleted file) closes that database's
idle connections at once. Leased ones are only ever closed by their own
thread on release.
Write path: the idle-exit write thread keeps its lock protocol; its
connection lives in a _WriteConnection holder that is reopened when the
generation moves, before the next task. Post-write schema_version check
and _after_write catalog await are kept for every write API in both
modes. Non-threaded write connections are reopened on a generation change
and never cached half-prepared.
Deleted files: write connections use mode=rw once Datasette has seen the
file exist (_file_seen), so a deleted file is never silently recreated,
while a database added before its file exists is still created by its
first write.
Settings: max_open_connections (clamped to >= 4 x num_sql_threads),
connection_idle_timeout_ms (30000, read connections and write threads),
schema_watch_interval_ms, default_schema_watch (external|owned). The
spike-only knobs (connection_idle_timeout, connection_pool_wait_ms,
pool_read_connections, write_thread_idle_timeout_ms) are gone, along with
the pool's wait/disable code paths. The reaper falls back to checkout-time
reaping where threads cannot be started (Pyodide).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwkLo2rJWidpkDVT3HkvNv
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
