Add per-table TTL refresh for tables without a change column

src/sqlmem/engine.py

@@ -22,6 +22,7 @@ class CachingEngine:
         self,
         source_engine: Engine,
         delta: dict[str, DeltaConfig] | None = None,
+        ttl: dict[str, int] | None = None,
     ) -> None:
         self._source_engine = source_engine
         self._cache = CacheManager(CACHE_DB_PATH, BACKUP_INTERVAL_SECONDS)
@@ -29,9 +30,18 @@ class CachingEngine:
         self._stats = StatsCollector()
         self._refresh_interval = REFRESH_INTERVAL_SECONDS
         self._delta = self._resolve_delta(delta or {})
+        self._ttl = dict(ttl or {})
         self._refresher = DeltaRefresher(self._cache, self._delta)
 
-        if self._delta:
+        overlap = set(self._delta) & set(self._ttl)
+        if overlap:
+            raise ValueError(
+                f"Tables {sorted(overlap)} are in both delta and ttl — a table is "
+                "either delta-refreshed (has a change column) or TTL-refreshed (full "
+                "reload), not both."
+            )
+
+        if self._delta or self._ttl:
             self._run_refresh()  # catch up tables restored from disk
             self._start_refresh_thread()
 
@@ -66,7 +76,7 @@ class CachingEngine:
         with self._source_engine.connect() as sa_conn:
             raw_conn = cast(sqlite3.Connection, sa_conn.connection.dbapi_connection)
             executor = QueryExecutor(
-                self._cache, self._registry, raw_conn, self._stats, self._delta
+                self._cache, self._registry, raw_conn, self._stats, self._delta, self._ttl
             )
             return executor.execute(parsed)
 
@@ -79,8 +89,25 @@ class CachingEngine:
             with self._source_engine.connect() as sa_conn:
                 raw_conn = cast(sqlite3.Connection, sa_conn.connection.dbapi_connection)
                 self._refresher.refresh(raw_conn)
+                self._refresh_ttl(raw_conn)
         except Exception as e:
-            logger.error(f"Delta refresh cycle failed: {e}")
+            logger.error(f"Refresh cycle failed: {e}")
+
+    def _refresh_ttl(self, source_conn: sqlite3.Connection) -> None:
+        """Proactively full-reload TTL-tracked tables whose cache has expired."""
+        for table, ttl in self._ttl.items():
+            if not self._cache.is_table_cached(table):
+                continue
+            age = self._cache.seconds_since_refresh(table)
+            if age is None or age <= ttl:
+                continue
+            try:
+                columns = self._cache.get_table_columns(table)
+                full = self._cache.is_table_full(table)
+                self._cache.load_table(table, columns, source_conn, full=full)
+                logger.info(f"TTL refresh {table!r}: reloaded (age {age:.0f}s > {ttl}s)")
+            except Exception as e:
+                logger.error(f"TTL refresh failed for {table!r}: {e}")
 
     def _start_refresh_thread(self) -> None:
         def loop() -> None: