[core] Optimize offline database schema

* Under the hood, SQLite creates surrogate keys (ROWID) anyway. We may as well take advantage of this and use the surrogates for foreign keys as well, since they are simpler and more efficient than compound foreign keys.
* Create indexes for efficient eviction queries

1 files changed, 1 insertions, 1 deletions

diff --git a/bin/offline.cpp b/bin/offline.cpp
index 79a091a534..a0adb6c2aa 100644
--- a/bin/offline.cpp
+++ b/bin/offline.cpp
@@ -12,7 +12,7 @@ using namespace std::literals::chrono_literals;
 int main(int, char * []) {
     using namespace mbgl;
 
-    util::deleteFile("offline.db");
+    unlink("offline.db");
 
     util::RunLoop loop;
     DefaultFileSource fileSource("offline.db", ".");