Add database migrations and handle leaving private chat portals. Fixes #7

database/upgrades/2019-05-16-message-delete-cascade.go

@@ -0,0 +1,25 @@
+package upgrades
+
+import (
+	"database/sql"
+)
+
+func init() {
+	upgrades[1] = upgrade{"Add ON DELETE CASCADE to message table", func(dialect Dialect, tx *sql.Tx) error {
+		if dialect == SQLite {
+			// SQLite doesn't support constraint updates, but it isn't that careful with constraints anyway.
+			return nil
+		}
+		_, err := tx.Exec("ALTER TABLE message DROP CONSTRAINT message_chat_jid_fkey")
+		if err != nil {
+			return err
+		}
+		_, err = tx.Exec(`ALTER TABLE message ADD CONSTRAINT message_chat_jid_fkey
+				FOREIGN KEY (chat_jid, chat_receiver) REFERENCES portal(jid, receiver)
+				ON DELETE CASCADE`)
+		if err != nil {
+			return err
+		}
+		return nil
+	}}
+}