diff --git a/benchmarks/benches/indexing.rs b/benchmarks/benches/indexing.rs
index 80c7ba0ed..81b21b5ea 100644
--- a/benchmarks/benches/indexing.rs
+++ b/benchmarks/benches/indexing.rs
@@ -170,12 +170,13 @@ fn reindexing_songs_default(c: &mut Criterion) {
                 let config = IndexerConfig::default();
                 let indexing_config = IndexDocumentsConfig::default();
                 let mut wtxn = index.write_txn().unwrap();
-                let mut builder =
+                let builder =
                     IndexDocuments::new(&mut wtxn, &index, &config, indexing_config, |_| ())
                         .unwrap();
 
                 let documents = utils::documents_from(datasets_paths::SMOL_SONGS, "csv");
-                builder.add_documents(documents).unwrap();
+                let (builder, user_error) = builder.add_documents(documents).unwrap();
+                user_error.unwrap();
                 builder.execute().unwrap();
                 wtxn.commit().unwrap();
 
@@ -185,12 +186,13 @@ fn reindexing_songs_default(c: &mut Criterion) {
                 let config = IndexerConfig::default();
                 let indexing_config = IndexDocumentsConfig::default();
                 let mut wtxn = index.write_txn().unwrap();
-                let mut builder =
+                let builder =
                     IndexDocuments::new(&mut wtxn, &index, &config, indexing_config, |_| ())
                         .unwrap();
 
                 let documents = utils::documents_from(datasets_paths::SMOL_SONGS, "csv");
-                builder.add_documents(documents).unwrap();
+                let (builder, user_error) = builder.add_documents(documents).unwrap();
+                user_error.unwrap();
                 builder.execute().unwrap();
                 wtxn.commit().unwrap();
 
@@ -460,12 +462,13 @@ fn reindexing_wiki(c: &mut Criterion) {
                 let indexing_config =
                     IndexDocumentsConfig { autogenerate_docids: true, ..Default::default() };
                 let mut wtxn = index.write_txn().unwrap();
-                let mut builder =
+                let builder =
                     IndexDocuments::new(&mut wtxn, &index, &config, indexing_config, |_| ())
                         .unwrap();
 
                 let documents = utils::documents_from(datasets_paths::SMOL_WIKI_ARTICLES, "csv");
-                builder.add_documents(documents).unwrap();
+                let (builder, user_error) = builder.add_documents(documents).unwrap();
+                user_error.unwrap();
                 builder.execute().unwrap();
                 wtxn.commit().unwrap();
 
@@ -476,12 +479,13 @@ fn reindexing_wiki(c: &mut Criterion) {
                 let indexing_config =
                     IndexDocumentsConfig { autogenerate_docids: true, ..Default::default() };
                 let mut wtxn = index.write_txn().unwrap();
-                let mut builder =
+                let builder =
                     IndexDocuments::new(&mut wtxn, &index, &config, indexing_config, |_| ())
                         .unwrap();
 
                 let documents = utils::documents_from(datasets_paths::SMOL_WIKI_ARTICLES, "csv");
-                builder.add_documents(documents).unwrap();
+                let (builder, user_error) = builder.add_documents(documents).unwrap();
+                user_error.unwrap();
                 builder.execute().unwrap();
                 wtxn.commit().unwrap();
 
@@ -680,12 +684,13 @@ fn reindexing_movies_default(c: &mut Criterion) {
                 let config = IndexerConfig::default();
                 let indexing_config = IndexDocumentsConfig::default();
                 let mut wtxn = index.write_txn().unwrap();
-                let mut builder =
+                let builder =
                     IndexDocuments::new(&mut wtxn, &index, &config, indexing_config, |_| ())
                         .unwrap();
 
                 let documents = utils::documents_from(datasets_paths::MOVIES, "json");
-                builder.add_documents(documents).unwrap();
+                let (builder, user_error) = builder.add_documents(documents).unwrap();
+                user_error.unwrap();
                 builder.execute().unwrap();
                 wtxn.commit().unwrap();
 
@@ -695,12 +700,13 @@ fn reindexing_movies_default(c: &mut Criterion) {
                 let config = IndexerConfig::default();
                 let indexing_config = IndexDocumentsConfig::default();
                 let mut wtxn = index.write_txn().unwrap();
-                let mut builder =
+                let builder =
                     IndexDocuments::new(&mut wtxn, &index, &config, indexing_config, |_| ())
                         .unwrap();
 
                 let documents = utils::documents_from(datasets_paths::MOVIES, "json");
-                builder.add_documents(documents).unwrap();
+                let (builder, user_error) = builder.add_documents(documents).unwrap();
+                user_error.unwrap();
                 builder.execute().unwrap();
                 wtxn.commit().unwrap();
 
@@ -1079,12 +1085,13 @@ fn reindexing_geo(c: &mut Criterion) {
                 let config = IndexerConfig::default();
                 let indexing_config = IndexDocumentsConfig::default();
                 let mut wtxn = index.write_txn().unwrap();
-                let mut builder =
+                let builder =
                     IndexDocuments::new(&mut wtxn, &index, &config, indexing_config, |_| ())
                         .unwrap();
 
                 let documents = utils::documents_from(datasets_paths::SMOL_ALL_COUNTRIES, "jsonl");
-                builder.add_documents(documents).unwrap();
+                let (builder, user_error) = builder.add_documents(documents).unwrap();
+                user_error.unwrap();
                 builder.execute().unwrap();
 
                 wtxn.commit().unwrap();
@@ -1095,12 +1102,13 @@ fn reindexing_geo(c: &mut Criterion) {
                 let config = IndexerConfig::default();
                 let indexing_config = IndexDocumentsConfig::default();
                 let mut wtxn = index.write_txn().unwrap();
-                let mut builder =
+                let builder =
                     IndexDocuments::new(&mut wtxn, &index, &config, indexing_config, |_| ())
                         .unwrap();
 
                 let documents = utils::documents_from(datasets_paths::SMOL_ALL_COUNTRIES, "jsonl");
-                builder.add_documents(documents).unwrap();
+                let (builder, user_error) = builder.add_documents(documents).unwrap();
+                user_error.unwrap();
                 builder.execute().unwrap();
 
                 wtxn.commit().unwrap();
diff --git a/benchmarks/benches/utils.rs b/benchmarks/benches/utils.rs
index 51178b43b..fba05edbe 100644
--- a/benchmarks/benches/utils.rs
+++ b/benchmarks/benches/utils.rs
@@ -1,7 +1,7 @@
 #![allow(dead_code)]
 
 use std::fs::{create_dir_all, remove_dir_all, File};
-use std::io::{self, BufReader, Cursor, Read, Seek};
+use std::io::{self, BufRead, BufReader, Cursor, Read, Seek};
 use std::num::ParseFloatError;
 use std::path::Path;
 
@@ -138,7 +138,7 @@ pub fn run_benches(c: &mut criterion::Criterion, confs: &[Conf]) {
     }
 }
 
-pub fn documents_from(filename: &str, filetype: &str) -> DocumentBatchReader<impl BufRead + Seek> {
+pub fn documents_from(filename: &str, filetype: &str) -> DocumentsBatchReader<impl BufRead + Seek> {
     let reader =
         File::open(filename).expect(&format!("could not find the dataset in: {}", filename));
     let reader = BufReader::new(reader);
diff --git a/milli/src/update/index_documents/enrich.rs b/milli/src/update/index_documents/enrich.rs
index 56f8fa4c0..51495c598 100644
--- a/milli/src/update/index_documents/enrich.rs
+++ b/milli/src/update/index_documents/enrich.rs
@@ -30,7 +30,7 @@ pub fn enrich_documents_batch<R: Read + Seek>(
     let mut cursor = reader.into_cursor();
     let mut documents_batch_index = cursor.documents_batch_index().clone();
     let mut external_ids = tempfile::tempfile().map(grenad::Writer::new)?;
-    let mut uuid_buffer = [0; uuid::adapter::Hyphenated::LENGTH];
+    let mut uuid_buffer = [0; uuid::fmt::Hyphenated::LENGTH];
 
     // The primary key *field id* that has already been set for this index or the one
     // we will guess by searching for the first key that contains "id" as a substring.
@@ -119,7 +119,7 @@ fn fetch_or_generate_document_id(
     documents_batch_index: &DocumentsBatchIndex,
     primary_key: PrimaryKey,
     autogenerate_docids: bool,
-    uuid_buffer: &mut [u8; uuid::adapter::Hyphenated::LENGTH],
+    uuid_buffer: &mut [u8; uuid::fmt::Hyphenated::LENGTH],
     count: u32,
 ) -> Result<StdResult<DocumentId, UserError>> {
     match primary_key {
@@ -134,7 +134,7 @@ fn fetch_or_generate_document_id(
                     }
                 }
                 None if autogenerate_docids => {
-                    let uuid = uuid::Uuid::new_v4().to_hyphenated().encode_lower(uuid_buffer);
+                    let uuid = uuid::Uuid::new_v4().as_hyphenated().encode_lower(uuid_buffer);
                     Ok(Ok(DocumentId::generated(uuid.to_string(), count)))
                 }
                 None => Ok(Err(UserError::MissingDocumentId {