diff --git a/meilidb-data/src/database.rs b/meilidb-data/src/database.rs
index 357693ad8..da43dd4bc 100644
--- a/meilidb-data/src/database.rs
+++ b/meilidb-data/src/database.rs
@@ -251,8 +251,12 @@ impl RawIndex {
         Ok(())
     }
 
-    pub fn update_ranked_map(&self, ranked_map: Arc<RankedMap>) {
-        self.ranked_map.store(ranked_map)
+    pub fn update_ranked_map(&self, ranked_map: Arc<RankedMap>) -> sled::Result<()> {
+        let data = bincode::serialize(ranked_map.as_ref()).unwrap();
+        self.inner.set("ranked-map", data).map(drop)?;
+        self.ranked_map.store(ranked_map);
+
+        Ok(())
     }
 
     pub fn set_document_attribute<V>(
@@ -343,7 +347,8 @@ impl Index {
 
     pub fn documents_addition(&self) -> DocumentsAddition {
         let index = self.0.clone();
-        DocumentsAddition::from_raw(index)
+        let ranked_map = self.0.ranked_map().clone();
+        DocumentsAddition::from_raw(index, ranked_map)
     }
 
     pub fn documents_deletion(&self) -> DocumentsDeletion {
@@ -381,11 +386,12 @@ impl Index {
 pub struct DocumentsAddition {
     inner: RawIndex,
     indexer: Indexer,
+    ranked_map: RankedMap,
 }
 
 impl DocumentsAddition {
-    pub fn from_raw(inner: RawIndex) -> DocumentsAddition {
-        DocumentsAddition { inner, indexer: Indexer::new() }
+    pub fn from_raw(inner: RawIndex, ranked_map: RankedMap) -> DocumentsAddition {
+        DocumentsAddition { inner, indexer: Indexer::new(), ranked_map }
     }
 
     pub fn update_document<D>(&mut self, document: D) -> Result<(), Error>
@@ -403,6 +409,7 @@ impl DocumentsAddition {
             schema,
             index: &self.inner,
             indexer: &mut self.indexer,
+            ranked_map: &mut self.ranked_map,
             document_id,
         };
 
@@ -430,7 +437,10 @@ pub struct DocumentsDeletion {
 
 impl DocumentsDeletion {
     pub fn from_raw(inner: RawIndex) -> DocumentsDeletion {
-        DocumentsDeletion { inner, documents: Vec::new() }
+        DocumentsDeletion {
+            inner,
+            documents: Vec::new(),
+        }
     }
 
     pub fn delete_document(&mut self, id: DocumentId) {
diff --git a/meilidb-data/src/number.rs b/meilidb-data/src/number.rs
index 9a2d0ea24..5e64cc78f 100644
--- a/meilidb-data/src/number.rs
+++ b/meilidb-data/src/number.rs
@@ -36,7 +36,7 @@ impl FromStr for Number {
     }
 }
 
-#[derive(Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub struct ParseNumberError {
     uint_error: ParseIntError,
     int_error: ParseIntError,
diff --git a/meilidb-data/src/serde/convert_to_number.rs b/meilidb-data/src/serde/convert_to_number.rs
new file mode 100644
index 000000000..57223a6c1
--- /dev/null
+++ b/meilidb-data/src/serde/convert_to_number.rs
@@ -0,0 +1,180 @@
+use std::str::FromStr;
+
+use ordered_float::OrderedFloat;
+use serde::ser;
+use serde::Serialize;
+
+use super::SerializerError;
+use crate::Number;
+
+pub struct ConvertToNumber;
+
+impl ser::Serializer for ConvertToNumber {
+    type Ok = Number;
+    type Error = SerializerError;
+    type SerializeSeq = ser::Impossible<Self::Ok, Self::Error>;
+    type SerializeTuple = ser::Impossible<Self::Ok, Self::Error>;
+    type SerializeTupleStruct = ser::Impossible<Self::Ok, Self::Error>;
+    type SerializeTupleVariant = ser::Impossible<Self::Ok, Self::Error>;
+    type SerializeMap = ser::Impossible<Self::Ok, Self::Error>;
+    type SerializeStruct = ser::Impossible<Self::Ok, Self::Error>;
+    type SerializeStructVariant = ser::Impossible<Self::Ok, Self::Error>;
+
+    fn serialize_bool(self, value: bool) -> Result<Self::Ok, Self::Error> {
+        Ok(Number::Unsigned(u64::from(value)))
+    }
+
+    fn serialize_char(self, value: char) -> Result<Self::Ok, Self::Error> {
+        unimplemented!()
+    }
+
+    fn serialize_i8(self, value: i8) -> Result<Self::Ok, Self::Error> {
+        Ok(Number::Signed(i64::from(value)))
+    }
+
+    fn serialize_i16(self, value: i16) -> Result<Self::Ok, Self::Error> {
+        Ok(Number::Signed(i64::from(value)))
+    }
+
+    fn serialize_i32(self, value: i32) -> Result<Self::Ok, Self::Error> {
+        Ok(Number::Signed(i64::from(value)))
+    }
+
+    fn serialize_i64(self, value: i64) -> Result<Self::Ok, Self::Error> {
+        Ok(Number::Signed(value))
+    }
+
+    fn serialize_u8(self, value: u8) -> Result<Self::Ok, Self::Error> {
+        Ok(Number::Unsigned(u64::from(value)))
+    }
+
+    fn serialize_u16(self, value: u16) -> Result<Self::Ok, Self::Error> {
+        Ok(Number::Unsigned(u64::from(value)))
+    }
+
+    fn serialize_u32(self, value: u32) -> Result<Self::Ok, Self::Error> {
+        Ok(Number::Unsigned(u64::from(value)))
+    }
+
+    fn serialize_u64(self, value: u64) -> Result<Self::Ok, Self::Error> {
+        Ok(Number::Unsigned(value))
+    }
+
+    fn serialize_f32(self, value: f32) -> Result<Self::Ok, Self::Error> {
+        Ok(Number::Float(OrderedFloat(value as f64)))
+    }
+
+    fn serialize_f64(self, value: f64) -> Result<Self::Ok, Self::Error> {
+        Ok(Number::Float(OrderedFloat(value)))
+    }
+
+    fn serialize_str(self, value: &str) -> Result<Self::Ok, Self::Error> {
+        Ok(Number::from_str(value)?)
+    }
+
+    fn serialize_bytes(self, _v: &[u8]) -> Result<Self::Ok, Self::Error> {
+        Err(SerializerError::UnserializableType { type_name: "&[u8]" })
+    }
+
+    fn serialize_none(self) -> Result<Self::Ok, Self::Error> {
+        Err(SerializerError::UnserializableType { type_name: "Option" })
+    }
+
+    fn serialize_some<T: ?Sized>(self, _value: &T) -> Result<Self::Ok, Self::Error>
+    where T: Serialize,
+    {
+        Err(SerializerError::UnserializableType { type_name: "Option" })
+    }
+
+    fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
+        Err(SerializerError::UnserializableType { type_name: "()" })
+    }
+
+    fn serialize_unit_struct(self, _name: &'static str) -> Result<Self::Ok, Self::Error> {
+        Err(SerializerError::UnserializableType { type_name: "unit struct" })
+    }
+
+    fn serialize_unit_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str
+    ) -> Result<Self::Ok, Self::Error>
+    {
+        Err(SerializerError::UnserializableType { type_name: "unit variant" })
+    }
+
+    fn serialize_newtype_struct<T: ?Sized>(
+        self,
+        _name: &'static str,
+        value: &T
+    ) -> Result<Self::Ok, Self::Error>
+    where T: Serialize,
+    {
+        value.serialize(self)
+    }
+
+    fn serialize_newtype_variant<T: ?Sized>(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _value: &T
+    ) -> Result<Self::Ok, Self::Error>
+    where T: Serialize,
+    {
+        Err(SerializerError::UnserializableType { type_name: "newtype variant" })
+    }
+
+    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
+        Err(SerializerError::UnserializableType { type_name: "sequence" })
+    }
+
+    fn serialize_tuple(self, _len: usize) -> Result<Self::SerializeTuple, Self::Error> {
+        Err(SerializerError::UnserializableType { type_name: "tuple" })
+    }
+
+    fn serialize_tuple_struct(
+        self,
+        _name: &'static str,
+        _len: usize
+    ) -> Result<Self::SerializeTupleStruct, Self::Error>
+    {
+        Err(SerializerError::UnserializableType { type_name: "tuple struct" })
+    }
+
+    fn serialize_tuple_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _len: usize
+    ) -> Result<Self::SerializeTupleVariant, Self::Error>
+    {
+        Err(SerializerError::UnserializableType { type_name: "tuple variant" })
+    }
+
+    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
+        Err(SerializerError::UnserializableType { type_name: "map" })
+    }
+
+    fn serialize_struct(
+        self,
+        _name: &'static str,
+        _len: usize
+    ) -> Result<Self::SerializeStruct, Self::Error>
+    {
+        Err(SerializerError::UnserializableType { type_name: "struct" })
+    }
+
+    fn serialize_struct_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _len: usize
+    ) -> Result<Self::SerializeStructVariant, Self::Error>
+    {
+        Err(SerializerError::UnserializableType { type_name: "struct variant" })
+    }
+}
diff --git a/meilidb-data/src/serde/mod.rs b/meilidb-data/src/serde/mod.rs
index 94e3172dd..75209c574 100644
--- a/meilidb-data/src/serde/mod.rs
+++ b/meilidb-data/src/serde/mod.rs
@@ -8,27 +8,31 @@ macro_rules! forward_to_unserializable_type {
     }
 }
 
+mod convert_to_number;
+mod convert_to_string;
 mod deserializer;
 mod extract_document_id;
-mod convert_to_string;
 mod indexer;
 mod serializer;
 
 pub use self::deserializer::Deserializer;
 pub use self::extract_document_id::extract_document_id;
 pub use self::convert_to_string::ConvertToString;
+pub use self::convert_to_number::ConvertToNumber;
 pub use self::indexer::Indexer;
 pub use self::serializer::Serializer;
 
 use std::{fmt, error::Error};
 use rmp_serde::encode::Error as RmpError;
 use serde::ser;
+use crate::number::ParseNumberError;
 
 #[derive(Debug)]
 pub enum SerializerError {
     DocumentIdNotFound,
     RmpError(RmpError),
     SledError(sled::Error),
+    ParseNumberError(ParseNumberError),
     UnserializableType { type_name: &'static str },
     UnindexableType { type_name: &'static str },
     Custom(String),
@@ -48,6 +52,9 @@ impl fmt::Display for SerializerError {
             }
             SerializerError::RmpError(e) => write!(f, "rmp serde related error: {}", e),
             SerializerError::SledError(e) => write!(f, "sled related error: {}", e),
+            SerializerError::ParseNumberError(e) => {
+                write!(f, "error while trying to parse a number: {}", e)
+            },
             SerializerError::UnserializableType { type_name } => {
                 write!(f, "{} are not a serializable type", type_name)
             },
@@ -78,3 +85,9 @@ impl From<sled::Error> for SerializerError {
         SerializerError::SledError(error)
     }
 }
+
+impl From<ParseNumberError> for SerializerError {
+    fn from(error: ParseNumberError) -> SerializerError {
+        SerializerError::ParseNumberError(error)
+    }
+}
diff --git a/meilidb-data/src/serde/serializer.rs b/meilidb-data/src/serde/serializer.rs
index d71c87f14..37b3c7036 100644
--- a/meilidb-data/src/serde/serializer.rs
+++ b/meilidb-data/src/serde/serializer.rs
@@ -2,14 +2,16 @@ use meilidb_core::DocumentId;
 use serde::ser;
 
 use crate::database::RawIndex;
+use crate::ranked_map::RankedMap;
 use crate::indexer::Indexer as RawIndexer;
 use crate::schema::{Schema, SchemaAttr};
-use super::{SerializerError, ConvertToString, Indexer};
+use super::{SerializerError, ConvertToString, ConvertToNumber, Indexer};
 
 pub struct Serializer<'a> {
     pub schema: &'a Schema,
     pub index: &'a RawIndex,
     pub indexer: &'a mut RawIndexer,
+    pub ranked_map: &'a mut RankedMap,
     pub document_id: DocumentId,
 }
 
@@ -134,6 +136,7 @@ impl<'a> ser::Serializer for Serializer<'a> {
             document_id: self.document_id,
             index: self.index,
             indexer: self.indexer,
+            ranked_map: self.ranked_map,
             current_key_name: None,
         })
     }
@@ -149,6 +152,7 @@ impl<'a> ser::Serializer for Serializer<'a> {
             document_id: self.document_id,
             index: self.index,
             indexer: self.indexer,
+            ranked_map: self.ranked_map,
         })
     }
 
@@ -169,6 +173,7 @@ pub struct MapSerializer<'a> {
     document_id: DocumentId,
     index: &'a RawIndex,
     indexer: &'a mut RawIndexer,
+    ranked_map: &'a mut RankedMap,
     current_key_name: Option<String>,
 }
 
@@ -205,6 +210,7 @@ impl<'a> ser::SerializeMap for MapSerializer<'a> {
             self.document_id,
             self.index,
             self.indexer,
+            self.ranked_map,
             &key,
             value,
         )
@@ -220,6 +226,7 @@ pub struct StructSerializer<'a> {
     document_id: DocumentId,
     index: &'a RawIndex,
     indexer: &'a mut RawIndexer,
+    ranked_map: &'a mut RankedMap,
 }
 
 impl<'a> ser::SerializeStruct for StructSerializer<'a> {
@@ -238,6 +245,7 @@ impl<'a> ser::SerializeStruct for StructSerializer<'a> {
             self.document_id,
             self.index,
             self.indexer,
+            self.ranked_map,
             key,
             value,
         )
@@ -253,6 +261,7 @@ fn serialize_value<T: ?Sized>(
     document_id: DocumentId,
     index: &RawIndex,
     indexer: &mut RawIndexer,
+    ranked_map: &mut RankedMap,
     key: &str,
     value: &T,
 ) -> Result<(), SerializerError>
@@ -276,7 +285,9 @@ where T: ser::Serialize,
         }
 
         if props.is_ranked() {
-            unimplemented!()
+            let key = (document_id, attr);
+            let number = value.serialize(ConvertToNumber)?;
+            ranked_map.insert(key, number);
         }
     }