[core] Implement a vacuum strategy for the offline database

Enable `PRAGMA auto_vacuum = INCREMENTAL`, and perform a `PRAGMA incremental_vacuum` when deleting an offline region.

2 files changed, 28 insertions, 0 deletions

diff --git a/test/fixtures/offline/v2.db b/test/fixtures/offline/v2.db
new file mode 100644
index 0000000000..8fadec4abe
--- /dev/null
+++ b/test/fixtures/offline/v2.db
diff --git a/test/storage/offline_database.cpp b/test/storage/offline_database.cpp
index 23269a98ed..11d56c237b 100644
--- a/test/storage/offline_database.cpp
+++ b/test/storage/offline_database.cpp
@@ -7,6 +7,7 @@
 #include <mbgl/util/string.hpp>
 
 #include <gtest/gtest.h>
+#include <sqlite3.hpp>
 #include <sqlite3.h>
 #include <thread>
 #include <random>
@@ -660,3 +661,30 @@ TEST(OfflineDatabase, OfflineMapboxTileCount) {
     db.deleteRegion(std::move(region1));
     EXPECT_EQ(0, db.getOfflineMapboxTileCount());
 }
+
+static int databasePageCount(const std::string& path) {
+    mapbox::sqlite::Database db(path, mapbox::sqlite::ReadOnly);
+    mapbox::sqlite::Statement stmt = db.prepare("pragma page_count");
+    stmt.run();
+    return stmt.get<int>(0);
+}
+
+TEST(OfflineDatabase, MigrateFromV2Schema) {
+    using namespace mbgl;
+
+    // v2.db is a v2 database containing a single offline region with a small number of resources.
+
+    deleteFile("test/fixtures/offline/v3.db");
+    writeFile("test/fixtures/offline/v3.db", util::read_file("test/fixtures/offline/v2.db"));
+
+    {
+        OfflineDatabase db("test/fixtures/offline/v3.db", 0);
+        auto regions = db.listRegions();
+        for (auto& region : regions) {
+            db.deleteRegion(std::move(region));
+        }
+    }
+
+    EXPECT_LT(databasePageCount("test/fixtures/offline/v3.db"),
+              databasePageCount("test/fixtures/offline/v2.db"));
+}