[db] Add optimize storage to database object #700

agdb/src/db.rs

@@ -196,17 +196,14 @@ impl Db {
     }
 
     /// Flushes the underlying file and copies it
-    /// to `filename` path.
+    /// to `filename` path. Consider calling `optimize_storage()`
+    /// prior to this function to reduce the size of the storage
+    /// file. If speed is of the essence you may omit that operation
+    /// at expense of the file size.
     pub fn backup(&mut self, filename: &str) -> Result<(), DbError> {
         self.storage.backup(filename)
     }
 
-    /// Returns the filename that was used to
-    /// construct the database.
-    pub fn filename(&self) -> &str {
-        self.storage.filename()
-    }
-
     /// Executes immutable query:
     ///
     /// - Select elements
@@ -241,6 +238,21 @@ impl Db {
         self.transaction_mut(|transaction| transaction.exec_mut(query))
     }
 
+    /// Returns the filename that was used to
+    /// construct the database.
+    pub fn filename(&self) -> &str {
+        self.storage.filename()
+    }
+
+    /// Reclaims no longer used segments of the database file by packing all
+    /// used storage segments together. This operation is done automatically
+    /// when the database goes out of scope. In long running programs it might
+    /// be desired to perform the storage file optimization without fully shutting
+    /// down.
+    pub fn optimize_storage(&mut self) -> Result<(), DbError> {
+        self.storage.shrink_to_fit()
+    }
+
     /// Executes immutable transaction. The transaction is running a closure `f`
     /// that will receive `&Transaction` object to run `exec` queries as if run
     /// on the main database object. You shall specify the return type `T`

agdb/tests/db_test.rs

@@ -8,6 +8,7 @@ use agdb::QueryId;
 use std::sync::Arc;
 use std::sync::RwLock;
 use test_db::test_file::TestFile;
+use test_db::TestDb;
 
 #[allow(unused_imports)]
 #[test]
@@ -330,3 +331,23 @@ fn filename() {
     let db = Db::new(test_file.file_name()).unwrap();
     assert_eq!(db.filename(), test_file.file_name());
 }
+
+#[test]
+fn optimize_storage() {
+    let mut db = TestDb::new();
+
+    db.exec_mut(
+        QueryBuilder::insert()
+            .nodes()
+            .count(100)
+            .values_uniform(vec![("key", 123).into()])
+            .query(),
+        100,
+    );
+
+    let size = std::fs::metadata(db.db.filename()).unwrap().len();
+    db.db.optimize_storage().unwrap();
+    let optimized_size = std::fs::metadata(db.db.filename()).unwrap().len();
+
+    assert!(optimized_size < size);
+}