Make the Index return default values when value don't exist

src/index.rs

@@ -1,3 +1,5 @@
+use std::borrow::Cow;
+
 use anyhow::Context;
 use heed::types::*;
 use heed::{PolyDatabase, Database};
@@ -47,8 +49,8 @@ impl Index {
     }
 
     /// Returns the internal documents ids.
-    pub fn documents_ids(&self, rtxn: &heed::RoTxn) -> heed::Result<Option<RoaringBitmap>> {
+    pub fn documents_ids(&self, rtxn: &heed::RoTxn) -> heed::Result<RoaringBitmap> {
-        self.main.get::<_, Str, RoaringBitmapCodec>(rtxn, DOCUMENTS_IDS_KEY)
+        Ok(self.main.get::<_, Str, RoaringBitmapCodec>(rtxn, DOCUMENTS_IDS_KEY)?.unwrap_or_default())
     }
 
     /// Writes the users ids documents ids, a user id is a byte slice (i.e. `[u8]`)
@@ -59,10 +61,10 @@ impl Index {
 
     /// Returns the user ids documents ids map which associate the user ids (i.e. `[u8]`)
     /// with the internal ids (i.e. `u32`).
-    pub fn users_ids_documents_ids<'t>(&self, rtxn: &'t heed::RoTxn) -> anyhow::Result<Option<fst::Map<&'t [u8]>>> {
+    pub fn users_ids_documents_ids<'t>(&self, rtxn: &'t heed::RoTxn) -> anyhow::Result<fst::Map<Cow<'t, [u8]>>> {
         match self.main.get::<_, Str, ByteSlice>(rtxn, USERS_IDS_DOCUMENTS_IDS_KEY)? {
-            Some(bytes) => Ok(Some(fst::Map::new(bytes)?)),
+            Some(bytes) => Ok(fst::Map::new(bytes)?.map_data(Cow::Borrowed)?),
-            None => Ok(None),
+            None => Ok(fst::Map::default().map_data(Cow::Owned)?),
         }
     }
 
@@ -74,20 +76,20 @@ impl Index {
 
     /// Returns the fields ids map which associate the documents keys with an internal field id
     /// (i.e. `u8`), this field id is used to identify fields in the obkv documents.
-    pub fn fields_ids_map(&self, rtxn: &heed::RoTxn) -> heed::Result<Option<FieldsIdsMap>> {
+    pub fn fields_ids_map(&self, rtxn: &heed::RoTxn) -> heed::Result<FieldsIdsMap> {
-        self.main.get::<_, Str, SerdeJson<FieldsIdsMap>>(rtxn, FIELDS_IDS_MAP_KEY)
+        Ok(self.main.get::<_, Str, SerdeJson<FieldsIdsMap>>(rtxn, FIELDS_IDS_MAP_KEY)?.unwrap_or_default())
     }
 
     /// Writes the FST which is the words dictionnary of the engine.
-    pub fn put_fst<A: AsRef<[u8]>>(&self, wtxn: &mut heed::RwTxn, fst: &fst::Set<A>) -> heed::Result<()> {
+    pub fn put_words_fst<A: AsRef<[u8]>>(&self, wtxn: &mut heed::RwTxn, fst: &fst::Set<A>) -> heed::Result<()> {
         self.main.put::<_, Str, ByteSlice>(wtxn, WORDS_FST_KEY, fst.as_fst().as_bytes())
     }
 
     /// Returns the FST which is the words dictionnary of the engine.
-    pub fn fst<'t>(&self, rtxn: &'t heed::RoTxn) -> anyhow::Result<Option<fst::Set<&'t [u8]>>> {
+    pub fn words_fst<'t>(&self, rtxn: &'t heed::RoTxn) -> anyhow::Result<fst::Set<Cow<'t, [u8]>>> {
         match self.main.get::<_, Str, ByteSlice>(rtxn, WORDS_FST_KEY)? {
-            Some(bytes) => Ok(Some(fst::Set::new(bytes)?)),
+            Some(bytes) => Ok(fst::Set::new(bytes)?.map_data(Cow::Borrowed)?),
-            None => Ok(None),
+            None => Ok(fst::Set::default().map_data(Cow::Owned)?),
         }
     }
 
@@ -111,10 +113,7 @@ impl Index {
 
     /// Returns the number of documents indexed in the database.
     pub fn number_of_documents(&self, rtxn: &heed::RoTxn) -> anyhow::Result<usize> {
-        match self.documents_ids(rtxn)? {
+        Ok(self.documents_ids(rtxn).map(|docids| docids.len() as usize)?)
-            Some(docids) => Ok(docids.len() as usize),
-            None => Ok(0),
-        }
     }
 
     pub fn search<'a>(&'a self, rtxn: &'a heed::RoTxn) -> Search<'a> {