Merge #566

566: Introduce the copy_to_path method on the Index r=irevoire a=Kerollmops

Meilisearch needs this method to do snapshots.

Co-authored-by: Kerollmops <clement@meilisearch.com>

milli/src/index.rs

@@ -1,11 +1,12 @@
 use std::borrow::Cow;
 use std::collections::{HashMap, HashSet};
+use std::fs::File;
 use std::mem::size_of;
 use std::path::Path;
 
 use heed::flags::Flags;
 use heed::types::*;
-use heed::{Database, PolyDatabase, RoTxn, RwTxn};
+use heed::{CompactionOption, Database, PolyDatabase, RoTxn, RwTxn};
 use roaring::RoaringBitmap;
 use rstar::RTree;
 use time::OffsetDateTime;
@@ -214,6 +215,10 @@ impl Index {
         self.env.path()
     }
 
+    pub fn copy_to_path<P: AsRef<Path>>(&self, path: P, option: CompactionOption) -> Result<File> {
+        self.env.copy_to_path(path, option).map_err(Into::into)
+    }
+
     /// Returns an `EnvClosingEvent` that can be used to wait for the closing event,
     /// multiple threads can wait on this event.
     ///