Clocks

cry/database.py

@@ -45,6 +45,60 @@ SCHEMA_STATEMENTS = [
       ELSE status
     END
     """,
+    # The "clock" is a number that increments as we make changes. We use this
+    # to do reconciliation, and track which versions of other databases we
+    # have reconciled already.
+    """
+    INSERT INTO properties (name, value) VALUES ('clock', 1);
+
+    CREATE TRIGGER update_clock_on_feed_insert
+    AFTER INSERT ON feeds
+    BEGIN
+      UPDATE properties SET value=value + 1 WHERE name='clock';
+    END;
+
+    CREATE TRIGGER update_clock_on_feed_delete
+    AFTER DELETE ON feeds
+    BEGIN
+      UPDATE properties SET value=value + 1 WHERE name='clock';
+    END;
+
+    CREATE TRIGGER update_clock_on_feed_update
+    AFTER UPDATE ON feeds
+    WHEN (NEW.last_fetched_ts IS NOT OLD.last_fetched_ts)
+      OR (NEW.retry_after_ts IS NOT OLD.retry_after_ts)
+      OR (NEW.status IS NOT OLD.status)
+      OR (NEW.etag IS NOT OLD.etag)
+      OR (NEW.modified IS NOT OLD.modified)
+      OR (NEW.title IS NOT OLD.title)
+      OR (NEW.link IS NOT OLD.link)
+    BEGIN
+      UPDATE properties SET value=value + 1 WHERE name='clock';
+    END;
+
+    CREATE TRIGGER update_clock_on_entries_insert
+    AFTER INSERT ON entries
+    BEGIN
+      UPDATE properties SET value=value + 1 WHERE name='clock';
+    END;
+
+    CREATE TRIGGER update_clock_on_entries_delete
+    AFTER DELETE ON entries
+    BEGIN
+      UPDATE properties SET value=value + 1 WHERE name='clock';
+    END;
+
+    CREATE TRIGGER update_clock_on_entries_update
+    AFTER UPDATE ON entries
+    WHEN (NEW.id IS NOT OLD.id)
+      OR (NEW.inserted_at IS NOT OLD.inserted_at)
+      OR (NEW.feed_url IS NOT OLD.feed_url)
+      OR (NEW.title IS NOT OLD.title)
+      OR (NEW.link IS NOT OLD.link)
+    BEGIN
+      UPDATE properties SET value=value + 1 WHERE name='clock';
+    END;
+    """,
 ]
 
 
@@ -121,6 +175,9 @@ class Database:
         with self.db:
             return self._set_property(prop, value)
 
+    def get_clock(self) -> int:
+        return int(self.get_property("clock", 0))
+
     def ensure_database_schema(self):
         with self.db:
             self.db.execute(
@@ -133,11 +190,10 @@ class Database:
             )
             version = int(self._get_property("version", 0))
             for script in SCHEMA_STATEMENTS[version:]:
-                for statement in script.split(";"):
-                    try:
-                        self.db.execute(statement)
-                    except Exception as e:
-                        raise Exception(f"Error executing:\n{statement}") from e
+                try:
+                    self.db.executescript(script)
+                except Exception as e:
+                    raise Exception(f"Error executing:\n{script}") from e
             self._set_property("version", len(SCHEMA_STATEMENTS))
             self._set_property("origin", self.origin)
 
@@ -248,33 +304,7 @@ class Database:
 
     def load_meta(self, url: str) -> feed.FeedMeta | None:
         with self.db:
-            cursor = self.db.execute(
-                """
-                SELECT
-                  last_fetched_ts,
-                  retry_after_ts,
-                  status,
-                  etag,
-                  modified
-                FROM feeds
-                WHERE url=?
-                """,
-                [url],
-            )
-
-            row = cursor.fetchone()
-            if row is None:
-                return None
-
-            last_fetched_ts, retry_after_ts, status, etag, modified = row
-            return feed.FeedMeta(
-                url=url,
-                last_fetched_ts=last_fetched_ts,
-                retry_after_ts=retry_after_ts,
-                status=status,
-                etag=etag,
-                modified=modified,
-            )
+            return self._load_meta(url)
 
     def update_meta(self, f: feed.FeedMeta):
         with self.db:
@@ -475,3 +505,32 @@ class Database:
             [status, new_ts, meta.url],
         )
         return cursor.rowcount
+
+    def _load_meta(self, url: str) -> feed.FeedMeta | None:
+        cursor = self.db.execute(
+            """
+                SELECT
+                  last_fetched_ts,
+                  retry_after_ts,
+                  status,
+                  etag,
+                  modified
+                FROM feeds
+                WHERE url=?
+                """,
+            [url],
+        )
+
+        row = cursor.fetchone()
+        if row is None:
+            return None
+
+        last_fetched_ts, retry_after_ts, status, etag, modified = row
+        return feed.FeedMeta(
+            url=url,
+            last_fetched_ts=last_fetched_ts,
+            retry_after_ts=retry_after_ts,
+            status=status,
+            etag=etag,
+            modified=modified,
+        )