[core] Add API for clearing tile cache

2 files changed, 25 insertions, 0 deletions

diff --git a/platform/default/include/mbgl/storage/offline_database.hpp b/platform/default/include/mbgl/storage/offline_database.hpp
index 3de829e635..4e9ffcf028 100644
--- a/platform/default/include/mbgl/storage/offline_database.hpp
+++ b/platform/default/include/mbgl/storage/offline_database.hpp
@@ -58,6 +58,11 @@ public:
     // lookup, it will not get downloaded again.
     std::exception_ptr invalidateTileCache();
 
+    // Clear the tile cache, freeing resources. This operation can be
+    // potentially slow because it will trigger a VACUUM on SQLite,
+    // forcing the database to move pages on the filesystem.
+    std::exception_ptr clearTileCache();
+
     expected<OfflineRegions, std::exception_ptr> listRegions();
 
     expected<OfflineRegion, std::exception_ptr> createRegion(const OfflineRegionDefinition&,
diff --git a/platform/default/src/mbgl/storage/offline_database.cpp b/platform/default/src/mbgl/storage/offline_database.cpp
index 0b3bcc049f..b60828d3a7 100644
--- a/platform/default/src/mbgl/storage/offline_database.cpp
+++ b/platform/default/src/mbgl/storage/offline_database.cpp
@@ -624,6 +624,26 @@ std::exception_ptr OfflineDatabase::invalidateTileCache() try {
     return std::current_exception();
 }
 
+std::exception_ptr OfflineDatabase::clearTileCache() try {
+    // clang-format off
+    mapbox::sqlite::Query query{ getStatement(
+        "DELETE FROM tiles "
+        "WHERE id NOT IN ("
+        "    SELECT tile_id FROM region_tiles"
+        ")"
+    ) };
+    // clang-format on
+
+    query.run();
+
+    db->exec("PRAGMA incremental_vacuum");
+
+    return nullptr;
+} catch (const mapbox::sqlite::Exception& ex) {
+    handleError(ex, "clear tile cache");
+    return std::current_exception();
+}
+
 std::exception_ptr OfflineDatabase::invalidateRegion(int64_t regionID) try {
     {
         // clang-format off