[db] Add size() to public API #730 (#733)

add size()

agdb/src/db.rs

@@ -328,6 +328,17 @@ impl<Store: StorageData> DbImpl<Store> {
         result
     }
 
+    /// Returns the database size in bytes. Depending on the underlying storage
+    /// the physical size in hardware might be higher. For example for in-memory
+    /// storage this function reports used storage but actually allocated memory
+    /// will likely be higher (expecting database growth in order to prevent too
+    /// frequent allocations). For file based storages this number will be accurate
+    /// but the actually used space on disk will be higher up to the next file system
+    /// block size.
+    pub fn size(&self) -> u64 {
+        self.storage.len()
+    }
+
     pub(crate) fn commit(&mut self) -> Result<(), QueryError> {
         self.undo_stack.clear();
         Ok(())

agdb/src/storage/file_storage.rs

@@ -52,14 +52,12 @@ impl FileStorage {
 
 impl StorageData for FileStorage {
     fn backup(&mut self, name: &str) -> Result<(), DbError> {
-        self.flush()?;
         std::fs::copy(&self.filename, name)?;
         Ok(())
     }
 
     fn flush(&mut self) -> Result<(), DbError> {
-        self.wal.clear()?;
-        Ok(self.file.flush()?)
+        self.wal.clear()
     }
 
     fn len(&self) -> u64 {

agdb/tests/db_test.rs

@@ -358,9 +358,9 @@ fn optimize_storage() {
         100,
     );
 
-    let size = std::fs::metadata(db.db.filename()).unwrap().len();
+    let size = db.db.size();
     db.db.optimize_storage().unwrap();
-    let optimized_size = std::fs::metadata(db.db.filename()).unwrap().len();
+    let optimized_size = db.db.size();
 
     assert!(optimized_size < size);
 }