Put the documents MTBL back into LMDB

We makes sure to write the documents into a file before
memory mapping it and putting it into LMDB, this way we avoid
moving it to RAM

src/bin/infos.rs

@@ -96,7 +96,7 @@ fn main() -> anyhow::Result<()> {
         .open(&opt.database)?;
 
     // Open the LMDB database.
-    let index = Index::new(&env, opt.database)?;
+    let index = Index::new(&env)?;
     let rtxn = env.read_txn()?;
 
     match opt.command {
@@ -200,6 +200,11 @@ fn biggest_value_sizes(index: &Index, rtxn: &heed::RoTxn, limit: usize) -> anyho
             if heap.len() > limit { heap.pop(); }
         }
 
+        if let Some(documents) = index.main.get::<_, ByteSlice, ByteSlice>(rtxn, b"documents")? {
+            heap.push(Reverse((documents.len(), format!("documents"), main_name)));
+            if heap.len() > limit { heap.pop(); }
+        }
+
         for result in index.word_positions.as_polymorph().iter::<_, Str, ByteSlice>(rtxn)? {
             let (word, value) = result?;
             heap.push(Reverse((value.len(), word.to_string(), word_positions_name)));