WIP

- manual embedder
- multi embedders OK
- clippy + tests OK

meilisearch-types/src/error.rs

@@ -305,6 +305,7 @@ NoSpaceLeftOnDevice                   , System               , UNPROCESSABLE_ENT
 PayloadTooLarge                       , InvalidRequest       , PAYLOAD_TOO_LARGE ;
 TaskNotFound                          , InvalidRequest       , NOT_FOUND ;
 TooManyOpenFiles                      , System               , UNPROCESSABLE_ENTITY ;
+TooManyVectors                        , InvalidRequest       , BAD_REQUEST ;
 UnretrievableDocument                 , Internal             , BAD_REQUEST ;
 UnretrievableErrorCode                , InvalidRequest       , BAD_REQUEST ;
 UnsupportedMediaType                  , InvalidRequest       , UNSUPPORTED_MEDIA_TYPE ;
@@ -362,7 +363,9 @@ impl ErrorCode for milli::Error {
                     UserError::CriterionError(_) => Code::InvalidSettingsRankingRules,
                     UserError::InvalidGeoField { .. } => Code::InvalidDocumentGeoField,
                     UserError::InvalidVectorDimensions { .. } => Code::InvalidVectorDimensions,
+                    UserError::InvalidVectorsMapType { .. } => Code::InvalidVectorsType,
                     UserError::InvalidVectorsType { .. } => Code::InvalidVectorsType,
+                    UserError::TooManyVectors(_, _) => Code::TooManyVectors,
                     UserError::SortError(_) => Code::InvalidSearchSort,
                     UserError::InvalidMinTypoWordLenSetting(_, _) => {
                         Code::InvalidSettingsTypoTolerance

meilisearch/src/routes/indexes/search.rs

@@ -235,38 +235,42 @@ pub async fn embed(
     index_scheduler: &IndexScheduler,
     index: &milli::Index,
 ) -> Result<(), ResponseError> {
-    if let Some(VectorQuery::String(prompt)) = query.vector.take() {
+    match query.vector.take() {
-        let embedder_configs = index.embedding_configs(&index.read_txn()?)?;
+        Some(VectorQuery::String(prompt)) => {
-        let embedder = index_scheduler.embedders(embedder_configs)?;
+            let embedder_configs = index.embedding_configs(&index.read_txn()?)?;
+            let embedder = index_scheduler.embedders(embedder_configs)?;
 
-        let embedder_name = if let Some(HybridQuery {
+            let embedder_name =
-            semantic_ratio: _,
+                if let Some(HybridQuery { semantic_ratio: _, embedder: Some(embedder) }) =
-            embedder: Some(embedder),
+                    &query.hybrid
-        }) = &query.hybrid
+                {
-        {
+                    embedder
-            embedder
+                } else {
-        } else {
+                    "default"
-            "default"
+                };
-        };
 
-        let embeddings = embedder
+            let embeddings = embedder
-            .get(embedder_name)
+                .get(embedder_name)
-            .ok_or(milli::UserError::InvalidEmbedder(embedder_name.to_owned()))
+                .ok_or(milli::UserError::InvalidEmbedder(embedder_name.to_owned()))
-            .map_err(milli::Error::from)?
+                .map_err(milli::Error::from)?
-            .0
+                .0
-            .embed(vec![prompt])
+                .embed(vec![prompt])
-            .await
+                .await
-            .map_err(milli::vector::Error::from)
+                .map_err(milli::vector::Error::from)
-            .map_err(milli::Error::from)?
+                .map_err(milli::Error::from)?
-            .pop()
+                .pop()
-            .expect("No vector returned from embedding");
+                .expect("No vector returned from embedding");
 
-        if embeddings.iter().nth(1).is_some() {
+            if embeddings.iter().nth(1).is_some() {
-            warn!("Ignoring embeddings past the first one in long search query");
+                warn!("Ignoring embeddings past the first one in long search query");
-            query.vector = Some(VectorQuery::Vector(embeddings.iter().next().unwrap().to_vec()));
+                query.vector =
-        } else {
+                    Some(VectorQuery::Vector(embeddings.iter().next().unwrap().to_vec()));
-            query.vector = Some(VectorQuery::Vector(embeddings.into_inner()));
+            } else {
+                query.vector = Some(VectorQuery::Vector(embeddings.into_inner()));
+            }
         }
+        Some(vector) => query.vector = Some(vector),
+        None => {}
     };
     Ok(())
 }

meilisearch/src/search.rs

@@ -13,7 +13,7 @@ use meilisearch_types::deserr::DeserrJsonError;
 use meilisearch_types::error::deserr_codes::*;
 use meilisearch_types::heed::RoTxn;
 use meilisearch_types::index_uid::IndexUid;
-use meilisearch_types::milli::score_details::{ScoreDetails, ScoringStrategy};
+use meilisearch_types::milli::score_details::{self, ScoreDetails, ScoringStrategy};
 use meilisearch_types::milli::{FacetValueHit, OrderBy, SearchForFacetValues, VectorQuery};
 use meilisearch_types::settings::DEFAULT_PAGINATION_MAX_TOTAL_HITS;
 use meilisearch_types::{milli, Document};
@@ -562,8 +562,17 @@ pub fn perform_search(
             insert_geo_distance(sort, &mut document);
         }
 
-        /// FIXME: remove this or set to value from the score details
+        let mut semantic_score = None;
-        let semantic_score = None;
+        for details in &score {
+            if let ScoreDetails::Vector(score_details::Vector {
+                target_vector: _,
+                value_similarity: Some((_matching_vector, similarity)),
+            }) = details
+            {
+                semantic_score = Some(*similarity);
+                break;
+            }
+        }
 
         let ranking_score =
             query.show_ranking_score.then(|| ScoreDetails::global_score(score.iter()));
@@ -648,8 +657,10 @@ pub fn perform_search(
         hits: documents,
         hits_info,
         query: query.q.unwrap_or_default(),
-        // FIXME: display input vector
+        vector: match query.vector {
-        vector: None,
+            Some(VectorQuery::Vector(vector)) => Some(vector),
+            _ => None,
+        },
         processing_time_ms: before_search.elapsed().as_millis(),
         facet_distribution,
         facet_stats,

meilisearch/tests/dumps/mod.rs

@@ -77,7 +77,8 @@ async fn import_dump_v1_movie_raw() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###
     );
@@ -238,7 +239,8 @@ async fn import_dump_v1_movie_with_settings() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###
     );
@@ -385,7 +387,8 @@ async fn import_dump_v1_rubygems_with_settings() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###
     );
@@ -518,7 +521,8 @@ async fn import_dump_v2_movie_raw() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###
     );
@@ -663,7 +667,8 @@ async fn import_dump_v2_movie_with_settings() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###
     );
@@ -807,7 +812,8 @@ async fn import_dump_v2_rubygems_with_settings() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###
     );
@@ -940,7 +946,8 @@ async fn import_dump_v3_movie_raw() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###
     );
@@ -1085,7 +1092,8 @@ async fn import_dump_v3_movie_with_settings() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###
     );
@@ -1229,7 +1237,8 @@ async fn import_dump_v3_rubygems_with_settings() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###
     );
@@ -1362,7 +1371,8 @@ async fn import_dump_v4_movie_raw() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###
     );
@@ -1507,7 +1517,8 @@ async fn import_dump_v4_movie_with_settings() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###
     );
@@ -1651,7 +1662,8 @@ async fn import_dump_v4_rubygems_with_settings() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###
     );
@@ -1896,7 +1908,8 @@ async fn import_dump_v6_containing_experimental_features() {
       },
       "pagination": {
         "maxTotalHits": 1000
-      }
+      },
+      "embedders": {}
     }
     "###);
 

meilisearch/tests/search/mod.rs

@@ -876,7 +876,31 @@ async fn experimental_feature_vector_store() {
         }))
         .await;
     meili_snap::snapshot!(code, @"200 OK");
-    meili_snap::snapshot!(meili_snap::json_string!(response["hits"]), @"[]");
+    // vector search returns all documents that don't have vectors in the last bucket, like all sorts
+    meili_snap::snapshot!(meili_snap::json_string!(response["hits"]), @r###"
+    [
+      {
+        "title": "Shazam!",
+        "id": "287947"
+      },
+      {
+        "title": "Captain Marvel",
+        "id": "299537"
+      },
+      {
+        "title": "Escape Room",
+        "id": "522681"
+      },
+      {
+        "title": "How to Train Your Dragon: The Hidden World",
+        "id": "166428"
+      },
+      {
+        "title": "Gläss",
+        "id": "450465"
+      }
+    ]
+    "###);
 }
 
 #[cfg(feature = "default")]

meilisearch/tests/settings/get_settings.rs

@@ -54,7 +54,7 @@ async fn get_settings() {
     let (response, code) = index.settings().await;
     assert_eq!(code, 200);
     let settings = response.as_object().unwrap();
-    assert_eq!(settings.keys().len(), 15);
+    assert_eq!(settings.keys().len(), 16);
     assert_eq!(settings["displayedAttributes"], json!(["*"]));
     assert_eq!(settings["searchableAttributes"], json!(["*"]));
     assert_eq!(settings["filterableAttributes"], json!([]));
@@ -83,6 +83,7 @@ async fn get_settings() {
             "maxTotalHits": 1000,
         })
     );
+    assert_eq!(settings["embedders"], json!({}));
 }
 
 #[actix_rt::test]

milli/src/error.rs

@@ -114,8 +114,10 @@ only composed of alphanumeric characters (a-z A-Z 0-9), hyphens (-) and undersco
     InvalidGeoField(#[from] GeoError),
     #[error("Invalid vector dimensions: expected: `{}`, found: `{}`.", .expected, .found)]
     InvalidVectorDimensions { expected: usize, found: usize },
-    #[error("The `_vectors` field in the document with the id: `{document_id}` is not an array. Was expecting an array of floats or an array of arrays of floats but instead got `{value}`.")]
+    #[error("The `_vectors.{subfield}` field in the document with id: `{document_id}` is not an array. Was expecting an array of floats or an array of arrays of floats but instead got `{value}`.")]
-    InvalidVectorsType { document_id: Value, value: Value },
+    InvalidVectorsType { document_id: Value, value: Value, subfield: String },
+    #[error("The `_vectors` field in the document with id: `{document_id}` is not an object. Was expecting an object with a key for each embedder with manually provided vectors, but instead got `{value}`")]
+    InvalidVectorsMapType { document_id: Value, value: Value },
     #[error("{0}")]
     InvalidFilter(String),
     #[error("Invalid type for filter subexpression: expected: {}, found: {1}.", .0.join(", "))]
@@ -196,6 +198,8 @@ only composed of alphanumeric characters (a-z A-Z 0-9), hyphens (-) and undersco
     TooManyEmbedders(usize),
     #[error("Cannot find embedder with name {0}.")]
     InvalidEmbedder(String),
+    #[error("Too many vectors for document with id {0}: found {1}, but limited to 256.")]
+    TooManyVectors(String, usize),
 }
 
 impl From<crate::vector::Error> for Error {

milli/src/update/index_documents/extract/extract_vector_points.rs

@@ -73,6 +73,7 @@ pub fn extract_vector_points<R: io::Read + io::Seek>(
     indexer: GrenadParameters,
     field_id_map: &FieldsIdsMap,
     prompt: &Prompt,
+    embedder_name: &str,
 ) -> Result<ExtractedVectorPoints> {
     puffin::profile_function!();
 
@@ -115,89 +116,87 @@ pub fn extract_vector_points<R: io::Read + io::Seek>(
         // lazily get it when needed
         let document_id = || -> Value { from_utf8(external_id_bytes).unwrap().into() };
 
-        let delta = if let Some(value) = vectors_fid.and_then(|vectors_fid| obkv.get(vectors_fid)) {
+        let vectors_field = vectors_fid
-            let vectors_obkv = KvReaderDelAdd::new(value);
+            .and_then(|vectors_fid| obkv.get(vectors_fid))
-            match (vectors_obkv.get(DelAdd::Deletion), vectors_obkv.get(DelAdd::Addition)) {
+            .map(KvReaderDelAdd::new)
-                (Some(old), Some(new)) => {
+            .map(|obkv| to_vector_maps(obkv, document_id))
-                    // no autogeneration
+            .transpose()?;
-                    let del_vectors = extract_vectors(old, document_id)?;
-                    let add_vectors = extract_vectors(new, document_id)?;
 
-                    VectorStateDelta::ManualDelta(
+        let (del_map, add_map) = vectors_field.unzip();
-                        del_vectors.unwrap_or_default(),
+        let del_map = del_map.flatten();
-                        add_vectors.unwrap_or_default(),
+        let add_map = add_map.flatten();
-                    )
-                }
-                (None, Some(new)) => {
-                    // was possibly autogenerated, remove all vectors for that document
-                    let add_vectors = extract_vectors(new, document_id)?;
 
-                    VectorStateDelta::WasGeneratedNowManual(add_vectors.unwrap_or_default())
+        let del_value = del_map.and_then(|mut map| map.remove(embedder_name));
-                }
+        let add_value = add_map.and_then(|mut map| map.remove(embedder_name));
-                (Some(_old), None) => {
-                    // Do we keep this document?
-                    let document_is_kept = obkv
-                        .iter()
-                        .map(|(_, deladd)| KvReaderDelAdd::new(deladd))
-                        .any(|deladd| deladd.get(DelAdd::Addition).is_some());
-                    if document_is_kept {
-                        // becomes autogenerated
-                        VectorStateDelta::NowGenerated(prompt.render(
-                            obkv,
-                            DelAdd::Addition,
-                            field_id_map,
-                        )?)
-                    } else {
-                        VectorStateDelta::NowRemoved
-                    }
-                }
-                (None, None) => {
-                    // Do we keep this document?
-                    let document_is_kept = obkv
-                        .iter()
-                        .map(|(_, deladd)| KvReaderDelAdd::new(deladd))
-                        .any(|deladd| deladd.get(DelAdd::Addition).is_some());
 
-                    if document_is_kept {
+        let delta = match (del_value, add_value) {
-                        // Don't give up if the old prompt was failing
+            (Some(old), Some(new)) => {
-                        let old_prompt =
+                // no autogeneration
-                            prompt.render(obkv, DelAdd::Deletion, field_id_map).unwrap_or_default();
+                let del_vectors = extract_vectors(old, document_id, embedder_name)?;
-                        let new_prompt = prompt.render(obkv, DelAdd::Addition, field_id_map)?;
+                let add_vectors = extract_vectors(new, document_id, embedder_name)?;
-                        if old_prompt != new_prompt {
+
-                            log::trace!(
+                if add_vectors.len() > u8::MAX.into() {
-                                "🚀 Changing prompt from\n{old_prompt}\n===to===\n{new_prompt}"
+                    return Err(crate::Error::UserError(crate::UserError::TooManyVectors(
-                            );
+                        document_id().to_string(),
-                            VectorStateDelta::NowGenerated(new_prompt)
+                        add_vectors.len(),
-                        } else {
+                    )));
-                            log::trace!("⏭️ Prompt unmodified, skipping");
+                }
-                            VectorStateDelta::NoChange
+
-                        }
+                VectorStateDelta::ManualDelta(del_vectors, add_vectors)
-                    } else {
+            }
-                        VectorStateDelta::NowRemoved
+            (Some(_old), None) => {
-                    }
+                // Do we keep this document?
+                let document_is_kept = obkv
+                    .iter()
+                    .map(|(_, deladd)| KvReaderDelAdd::new(deladd))
+                    .any(|deladd| deladd.get(DelAdd::Addition).is_some());
+                if document_is_kept {
+                    // becomes autogenerated
+                    VectorStateDelta::NowGenerated(prompt.render(
+                        obkv,
+                        DelAdd::Addition,
+                        field_id_map,
+                    )?)
+                } else {
+                    VectorStateDelta::NowRemoved
                 }
             }
-        } else {
+            (None, Some(new)) => {
-            // Do we keep this document?
+                // was possibly autogenerated, remove all vectors for that document
-            let document_is_kept = obkv
+                let add_vectors = extract_vectors(new, document_id, embedder_name)?;
-                .iter()
+                if add_vectors.len() > u8::MAX.into() {
-                .map(|(_, deladd)| KvReaderDelAdd::new(deladd))
+                    return Err(crate::Error::UserError(crate::UserError::TooManyVectors(
-                .any(|deladd| deladd.get(DelAdd::Addition).is_some());
+                        document_id().to_string(),
-
+                        add_vectors.len(),
-            if document_is_kept {
+                    )));
-                // Don't give up if the old prompt was failing
+                }
-                let old_prompt =
+
-                    prompt.render(obkv, DelAdd::Deletion, field_id_map).unwrap_or_default();
+                VectorStateDelta::WasGeneratedNowManual(add_vectors)
-                let new_prompt = prompt.render(obkv, DelAdd::Addition, field_id_map)?;
+            }
-                if old_prompt != new_prompt {
+            (None, None) => {
-                    log::trace!("🚀 Changing prompt from\n{old_prompt}\n===to===\n{new_prompt}");
+                // Do we keep this document?
-                    VectorStateDelta::NowGenerated(new_prompt)
+                let document_is_kept = obkv
-                } else {
+                    .iter()
-                    log::trace!("⏭️ Prompt unmodified, skipping");
+                    .map(|(_, deladd)| KvReaderDelAdd::new(deladd))
-                    VectorStateDelta::NoChange
+                    .any(|deladd| deladd.get(DelAdd::Addition).is_some());
+
+                if document_is_kept {
+                    // Don't give up if the old prompt was failing
+                    let old_prompt =
+                        prompt.render(obkv, DelAdd::Deletion, field_id_map).unwrap_or_default();
+                    let new_prompt = prompt.render(obkv, DelAdd::Addition, field_id_map)?;
+                    if old_prompt != new_prompt {
+                        log::trace!(
+                            "🚀 Changing prompt from\n{old_prompt}\n===to===\n{new_prompt}"
+                        );
+                        VectorStateDelta::NowGenerated(new_prompt)
+                    } else {
+                        log::trace!("⏭️ Prompt unmodified, skipping");
+                        VectorStateDelta::NoChange
+                    }
+                } else {
+                    VectorStateDelta::NowRemoved
                 }
-            } else {
-                VectorStateDelta::NowRemoved
             }
         };
 
@@ -221,6 +220,34 @@ pub fn extract_vector_points<R: io::Read + io::Seek>(
     })
 }
 
+fn to_vector_maps(
+    obkv: KvReaderDelAdd,
+    document_id: impl Fn() -> Value,
+) -> Result<(Option<serde_json::Map<String, Value>>, Option<serde_json::Map<String, Value>>)> {
+    let del = to_vector_map(obkv, DelAdd::Deletion, &document_id)?;
+    let add = to_vector_map(obkv, DelAdd::Addition, &document_id)?;
+    Ok((del, add))
+}
+
+fn to_vector_map(
+    obkv: KvReaderDelAdd,
+    side: DelAdd,
+    document_id: &impl Fn() -> Value,
+) -> Result<Option<serde_json::Map<String, Value>>> {
+    Ok(if let Some(value) = obkv.get(side) {
+        let Ok(value) = from_slice(value) else {
+            let value = from_slice(value).map_err(InternalError::SerdeJson)?;
+            return Err(crate::Error::UserError(UserError::InvalidVectorsMapType {
+                document_id: document_id(),
+                value,
+            }));
+        };
+        Some(value)
+    } else {
+        None
+    })
+}
+
 /// Computes the diff between both Del and Add numbers and
 /// only inserts the parts that differ in the sorter.
 fn push_vectors_diff(
@@ -286,12 +313,20 @@ fn compare_vectors(a: &[f32], b: &[f32]) -> Ordering {
 }
 
 /// Extracts the vectors from a JSON value.
-fn extract_vectors(value: &[u8], document_id: impl Fn() -> Value) -> Result<Option<Vec<Vec<f32>>>> {
+fn extract_vectors(
-    match from_slice(value) {
+    value: Value,
-        Ok(vectors) => Ok(VectorOrArrayOfVectors::into_array_of_vectors(vectors)),
+    document_id: impl Fn() -> Value,
+    name: &str,
+) -> Result<Vec<Vec<f32>>> {
+    // FIXME: ugly clone of the vectors here
+    match serde_json::from_value(value.clone()) {
+        Ok(vectors) => {
+            Ok(VectorOrArrayOfVectors::into_array_of_vectors(vectors).unwrap_or_default())
+        }
         Err(_) => Err(UserError::InvalidVectorsType {
             document_id: document_id(),
-            value: from_slice(value).map_err(InternalError::SerdeJson)?,
+            value,
+            subfield: name.to_owned(),
         }
         .into()),
     }

milli/src/update/index_documents/extract/mod.rs

@@ -298,6 +298,7 @@ fn send_original_documents_data(
                 indexer,
                 &field_id_map,
                 &prompt,
+                &name,
             );
             match result {
                 Ok(ExtractedVectorPoints { manual_vectors, remove_vectors, prompts }) => {

milli/src/update/index_documents/mod.rs

@@ -514,16 +514,18 @@ where
         // We write the primary key field id into the main database
         self.index.put_primary_key(self.wtxn, &primary_key)?;
         let number_of_documents = self.index.number_of_documents(self.wtxn)?;
+        let mut rng = rand::rngs::StdRng::from_entropy();
 
         for (embedder_name, dimension) in dimension {
             let wtxn = &mut *self.wtxn;
             let vector_arroy = self.index.vector_arroy;
-            /// FIXME: unwrap
+
-            let embedder_index =
+            let embedder_index = self.index.embedder_category_id.get(wtxn, &embedder_name)?.ok_or(
-                self.index.embedder_category_id.get(wtxn, &embedder_name)?.unwrap();
+                InternalError::DatabaseMissingEntry { db_name: "embedder_category_id", key: None },
+            )?;
+
             pool.install(|| {
                 let writer_index = (embedder_index as u16) << 8;
-                let mut rng = rand::rngs::StdRng::from_entropy();
                 for k in 0..=u8::MAX {
                     let writer = arroy::Writer::prepare(
                         wtxn,

milli/src/update/index_documents/typed_chunk.rs

@@ -22,7 +22,9 @@ use crate::index::db_name::DOCUMENTS;
 use crate::update::del_add::{deladd_serialize_add_side, DelAdd, KvReaderDelAdd};
 use crate::update::facet::FacetsUpdate;
 use crate::update::index_documents::helpers::{as_cloneable_grenad, try_split_array_at};
-use crate::{lat_lng_to_xyz, DocumentId, FieldId, GeoPoint, Index, Result, SerializationError};
+use crate::{
+    lat_lng_to_xyz, DocumentId, FieldId, GeoPoint, Index, InternalError, Result, SerializationError,
+};
 
 pub(crate) enum TypedChunk {
     FieldIdDocidFacetStrings(grenad::Reader<CursorClonableMmap>),
@@ -363,8 +365,9 @@ pub(crate) fn write_typed_chunk_into_index(
             expected_dimension,
             embedder_name,
         } => {
-            /// FIXME: unwrap
+            let embedder_index = index.embedder_category_id.get(wtxn, &embedder_name)?.ok_or(
-            let embedder_index = index.embedder_category_id.get(wtxn, &embedder_name)?.unwrap();
+                InternalError::DatabaseMissingEntry { db_name: "embedder_category_id", key: None },
+            )?;
             let writer_index = (embedder_index as u16) << 8;
             // FIXME: allow customizing distance
             let writers: std::result::Result<Vec<_>, _> = (0..=u8::MAX)
@@ -404,7 +407,20 @@ pub(crate) fn write_typed_chunk_into_index(
                             // code error if we somehow got the wrong dimension
                             .unwrap();
 
-                    /// FIXME: detect overflow
+                    if embeddings.embedding_count() > u8::MAX.into() {
+                        let external_docid = if let Ok(Some(Ok(index))) = index
+                            .external_id_of(wtxn, std::iter::once(docid))
+                            .map(|it| it.into_iter().next())
+                        {
+                            index
+                        } else {
+                            format!("internal docid={docid}")
+                        };
+                        return Err(crate::Error::UserError(crate::UserError::TooManyVectors(
+                            external_docid,
+                            embeddings.embedding_count(),
+                        )));
+                    }
                     for (embedding, writer) in embeddings.iter().zip(&writers) {
                         writer.add_item(wtxn, docid, embedding)?;
                     }
@@ -455,7 +471,7 @@ pub(crate) fn write_typed_chunk_into_index(
                 if let Some(value) = vector_deladd_obkv.get(DelAdd::Addition) {
                     let vector = pod_collect_to_vec(value);
 
-                    /// FIXME: detect overflow
+                    // overflow was detected during vector extraction.
                     for writer in &writers {
                         if !writer.contains_item(wtxn, docid)? {
                             writer.add_item(wtxn, docid, &vector)?;

milli/src/vector/manual.rs

@@ -0,0 +1,34 @@
+use super::error::EmbedError;
+use super::Embeddings;
+
+#[derive(Debug, Clone, Copy)]
+pub struct Embedder {
+    dimensions: usize,
+}
+
+#[derive(Debug, Clone, Hash, PartialEq, Eq, serde::Deserialize, serde::Serialize)]
+pub struct EmbedderOptions {
+    pub dimensions: usize,
+}
+
+impl Embedder {
+    pub fn new(options: EmbedderOptions) -> Self {
+        Self { dimensions: options.dimensions }
+    }
+
+    pub fn embed(&self, mut texts: Vec<String>) -> Result<Vec<Embeddings<f32>>, EmbedError> {
+        let Some(text) = texts.pop() else { return Ok(Default::default()) };
+        Err(EmbedError::embed_on_manual_embedder(text))
+    }
+
+    pub fn dimensions(&self) -> usize {
+        self.dimensions
+    }
+
+    pub fn embed_chunks(
+        &self,
+        text_chunks: Vec<Vec<String>>,
+    ) -> Result<Vec<Vec<Embeddings<f32>>>, EmbedError> {
+        text_chunks.into_iter().map(|prompts| self.embed(prompts)).collect()
+    }
+}

milli/src/vector/mod.rs

@@ -31,6 +31,10 @@ impl<F> Embeddings<F> {
         Ok(this)
     }
 
+    pub fn embedding_count(&self) -> usize {
+        self.data.len() / self.dimension
+    }
+
     pub fn dimension(&self) -> usize {
         self.dimension
     }