Implement garbage collection without indexes

storage_engine/src/cursor.rs

@@ -518,18 +518,37 @@ impl <'cursor, T> WriteCursor<'cursor, T>
         where T: Send + Decode + Encode
     {
         let mut cursor_to_intermediate = self.spawn_cursor_to_intermediate_file().await?;
-
+        // This will be a vector of such BTree maps...
         let in_memory_index: BTreeMap<T, HashSet<FilePosition>> = BTreeMap::new();
 
         // We'll dump all alive entries into a new file.
-        while let Some(live_entry) = self.next_alive().await? {
+        let mut entries_deleted = 0;
-            let file_position = cursor_to_intermediate.append_entry(&live_entry.forget()).await?;
+        {
-            // TODO: Start indexing all of the indexable columns from scratch.
+            while let Some(live_entry) = self.next_alive().await? {
+                entries_deleted += 1;
+                let file_position = cursor_to_intermediate.append_entry(&live_entry.forget()).await?;
+                // TODO: Start indexing all of the indexable columns from scratch.
+            }
         }
 
-        // In it there will be only the alive rows.
+        // TODO: Create a new indexes from in_memory_index.
+
         // Afterwards we swap the files, and delete the garbage.
-        todo!()
+        // TODO:
+        // What needs to be done?
+        // 1. We take self cursor and mutate it
+
+        // swapping headers
+        self.header.deleted_count = 0;
+        self.header.total_count = cursor_to_intermediate.header.total_count;
+
+        // TODO: We'll actually have to iterate through all the indexes and swap each of them.
+        self.indexes = todo!();
+        self.file = cursor_to_intermediate.file;
+
+        self.eof_file_position = cursor_to_intermediate.eof_file_position;
+
+        Ok(entries_deleted)
     }
 
     async fn spawn_cursor_to_intermediate_file(&self) -> Result<AppendOnlyCursor<T>>