diff --git a/milli/src/update/new/indexer/document_operation.rs b/milli/src/update/new/indexer/document_operation.rs
index c54ffd140..29f36a82e 100644
--- a/milli/src/update/new/indexer/document_operation.rs
+++ b/milli/src/update/new/indexer/document_operation.rs
@@ -338,3 +338,122 @@ fn merge_document_for_updates(
         }
     }
 }
+
+/*
+
+
+use std::{
+    borrow::{Borrow, Cow},
+    collections::BTreeMap,
+    ops::Deref,
+};
+
+use serde::Deserialize;
+use serde_json::{value::RawValue, Value};
+/*
+#[repr(transparent)]
+pub struct my_str(str);
+
+impl ToOwned for my_str {
+    type Owned = Box<str>;
+
+    fn to_owned(&self) -> Self::Owned {
+        self.0.to_string().into_boxed_str()
+    }
+}
+
+impl Borrow<my_str> for Box<str> {
+    fn borrow(&self) -> &my_str {
+        unsafe { std::mem::transmute(self.as_ref()) }
+    }
+}
+*/
+
+#[derive(Deserialize, PartialEq, Eq, PartialOrd, Ord)]
+pub struct CowKey<'doc>(#[serde(borrow)] Cow<'doc, str>);
+
+impl<'doc> Borrow<str> for CowKey<'doc> {
+    fn borrow(&self) -> &str {
+        self.0.borrow()
+    }
+}
+
+#[derive(Deserialize)]
+pub struct TopLevelMap<'doc>(#[serde(borrow)] BTreeMap<CowKey<'doc>, &'doc RawValue>);
+
+#[derive(Deserialize)]
+pub struct FlatDocs<'doc>(#[serde(borrow)] Vec<&'doc RawValue>);
+
+fn read_docs<'doc>(
+    ndjson: &'doc str,
+) -> impl Iterator<Item = Result<TopLevelMap<'doc>, serde_json::Error>> {
+    serde_json::Deserializer::from_str(ndjson).into_iter::<TopLevelMap>()
+}
+
+fn main() {
+    let ndjson_data = r#"
+        {
+            "id": {
+                "nested": "kefir"
+            },
+            "name": "Alice",
+            "age": 30
+        }
+        {
+            "id": {
+                "nested": "intel"
+            },
+            "name\n": "Bob",
+            "age": 22
+        }
+    "#;
+
+    let primary_key: Vec<_> = "id.nested".split('.').collect(); // dynamic
+
+    for doc in read_docs(ndjson_data) {
+        let doc = doc.unwrap();
+        let docid = get_docid(&doc, &primary_key).unwrap().expect("missingno");
+        println!("docid={docid}");
+    }
+}
+
+pub struct Document<'payload> {
+    fields: TopLevelMap<'payload>,
+    docid: String,
+}
+
+/*impl<'payload> Document<'payload> {
+    pub fn get(name: &str) -> Option<&'payload RawValue> {}
+
+    pub fn get_nested(name: &[&str]) {}
+}*/
+
+fn get_docid<'payload>(
+    map: &TopLevelMap<'payload>,
+    primary_key: &[&str],
+) -> serde_json::Result<Option<CowKey<'payload>>> {
+    match primary_key {
+        [] => unreachable!("arrrgh"),
+        [primary_key] => match map.0.get(*primary_key) {
+            Some(value) => {
+                let value = value.get();
+                let value_number: Result<u64, _> = serde_json::from_str(value);
+                Ok(Some(match value_number {
+                    Ok(value) => CowKey(Cow::Owned(value.to_string())),
+                    Err(_) => serde_json::from_str(value)?,
+                }))
+            }
+            None => Ok(None),
+        },
+        [head, tail @ ..] => match map.0.get(*head) {
+            Some(value) => {
+                let map = serde_json::from_str(value.get())?;
+                get_docid(&map, tail)
+            }
+            None => Ok(None),
+        },
+    }
+}
+
+
+*/