Merge #4631

4631: Split the field id map from the weight of each fields r=Kerollmops a=irevoire

# Pull Request

## Related issue
Fixes https://github.com/meilisearch/meilisearch/issues/4484

## What does this PR do?
- Make the (internal) searchable fields database always contain the searchable fields (instead of None when the user-defined searchable fields were not defined)
- Introduce a new « fieldids_weights_map » that does the mapping between a fieldId and its Weight
- Ensure that when two searchable fields are swapped, the field ID map doesn't change anymore (and thus, doesn't re-index)
- Uses the weight instead of the order of the searchable fields in the attribute ranking rule at search time
- When no searchable attributes are defined, make all their weights equal to zero
- When a field is declared as searchable and contains nested fields, all its subfields share the same weight

## Impact on relevancy

### When no searchable attributes are declared

When no searchable attributes are declared, all the fields have the same importance instead of randomly giving more importance to the field we've encountered « the most early » in the life of the index.

This means that before this PR, send the following json:
```json
[
  { "id": 0, "name": "kefir", "color": "white" },
  { "id": 1, "name": "white", "last name": "spirit" }
]
```

Would make the field `name` more important than the field `color` or `last name`.
This means that searching for `white` would make the document `1` automatically higher ranked than the document `0`.

After this PR, all the fields have the same weight, and none are considered more important than others.

### When a nested field is made searchable

The second behavior change that happened with this PR is in the case you're sending this document, for example:

```json
{
  "id": 0,
  "name": "tamo",
  "doggo": {
    "name": "kefir",
    "surname": "le kef"
  },
  "catto": "gromez"
}
```

Previously, defining the searchable attributes as: `["tamo", "doggo", "catto"]` was actually defining the « real » searchable attributes in the engine as: `["tamo", "doggo", "catto", "doggo.name", "doggo.surname"]`, which means that `doggo.name` and `doggo.surname` were _NOT_ where the user expected them and had completely different weights than `doggo`.
In this PR all the weights have been unified, and the « real » searchable fields look like this:
```json
[ "tamo", "doggo", "doggo.name", "doggo.surname", "catto"]
   ^^^^    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^    ^^^^^
Weight 0                 Weight 1                  Weight 2

Co-authored-by: Tamo <tamo@meilisearch.com>

index-scheduler/src/utils.rs

@@ -272,9 +272,9 @@ pub fn swap_index_uid_in_task(task: &mut Task, swap: (&str, &str)) {
     }
     for index_uid in index_uids {
         if index_uid == swap.0 {
-            *index_uid = swap.1.to_owned();
+            swap.1.clone_into(index_uid);
         } else if index_uid == swap.1 {
-            *index_uid = swap.0.to_owned();
+            swap.0.clone_into(index_uid);
         }
     }
 }

meilisearch/src/search.rs

@@ -730,7 +730,7 @@ pub fn perform_search(
         let mut ids = BTreeSet::new();
         for attr in attrs {
             if attr == "*" {
-                ids = displayed_ids.clone();
+                ids.clone_from(&displayed_ids);
                 break;
             }
 

meilisearch/src/search_queue.rs

@@ -85,8 +85,13 @@ impl SearchQueue {
                 },
 
                 search_request = receive_new_searches.recv() => {
-                    // this unwrap is safe because we're sure the `SearchQueue` still lives somewhere in actix-web
+                    let search_request = match search_request {
-                    let search_request = search_request.unwrap();
+                        Some(search_request) => search_request,
+                        // This should never happen while actix-web is running, but it's not a reason to crash
+                        // and it can generate a lot of noise in the tests.
+                        None => continue,
+                    };
+
                     if searches_running < usize::from(parallelism) && queue.is_empty() {
                         searches_running += 1;
                         // if the search requests die it's not a hard error on our side

meilisearch/tests/search/hybrid.rs

@@ -85,8 +85,8 @@ async fn simple_search() {
         )
         .await;
     snapshot!(code, @"200 OK");
-    snapshot!(response["hits"], @r###"[{"title":"Captain Planet","desc":"He's not part of the Marvel Cinematic Universe","id":"2","_vectors":{"default":[1.0,2.0]},"_rankingScore":0.996969696969697},{"title":"Captain Marvel","desc":"a Shazam ersatz","id":"3","_vectors":{"default":[2.0,3.0]},"_rankingScore":0.996969696969697},{"title":"Shazam!","desc":"a Captain Marvel ersatz","id":"1","_vectors":{"default":[1.0,3.0]},"_rankingScore":0.9472135901451112}]"###);
+    snapshot!(response["hits"], @r###"[{"title":"Captain Marvel","desc":"a Shazam ersatz","id":"3","_vectors":{"default":[2.0,3.0]},"_rankingScore":0.990290343761444},{"title":"Captain Planet","desc":"He's not part of the Marvel Cinematic Universe","id":"2","_vectors":{"default":[1.0,2.0]},"_rankingScore":0.9848484848484848},{"title":"Shazam!","desc":"a Captain Marvel ersatz","id":"1","_vectors":{"default":[1.0,3.0]},"_rankingScore":0.9472135901451112}]"###);
-    snapshot!(response["semanticHitCount"], @"1");
+    snapshot!(response["semanticHitCount"], @"2");
 
     let (response, code) = index
         .search_post(
@@ -331,7 +331,7 @@ async fn query_combination() {
     .await;
 
     snapshot!(code, @"200 OK");
-    snapshot!(response["hits"], @r###"[{"title":"Captain Planet","desc":"He's not part of the Marvel Cinematic Universe","id":"2","_vectors":{"default":[1.0,2.0]},"_rankingScore":0.996969696969697},{"title":"Captain Marvel","desc":"a Shazam ersatz","id":"3","_vectors":{"default":[2.0,3.0]},"_rankingScore":0.996969696969697},{"title":"Shazam!","desc":"a Captain Marvel ersatz","id":"1","_vectors":{"default":[1.0,3.0]},"_rankingScore":0.8848484848484849}]"###);
+    snapshot!(response["hits"], @r###"[{"title":"Captain Planet","desc":"He's not part of the Marvel Cinematic Universe","id":"2","_vectors":{"default":[1.0,2.0]},"_rankingScore":0.9848484848484848},{"title":"Captain Marvel","desc":"a Shazam ersatz","id":"3","_vectors":{"default":[2.0,3.0]},"_rankingScore":0.9848484848484848},{"title":"Shazam!","desc":"a Captain Marvel ersatz","id":"1","_vectors":{"default":[1.0,3.0]},"_rankingScore":0.9242424242424242}]"###);
     snapshot!(response["semanticHitCount"], @"null");
 
     // query + vector, no hybrid keyword =>
@@ -374,6 +374,6 @@ async fn query_combination() {
         .await;
 
     snapshot!(code, @"200 OK");
-    snapshot!(response["hits"], @r###"[{"title":"Captain Planet","desc":"He's not part of the Marvel Cinematic Universe","id":"2","_vectors":{"default":[1.0,2.0]},"_rankingScore":0.9848484848484848}]"###);
+    snapshot!(response["hits"], @r###"[{"title":"Captain Planet","desc":"He's not part of the Marvel Cinematic Universe","id":"2","_vectors":{"default":[1.0,2.0]},"_rankingScore":0.9242424242424242}]"###);
     snapshot!(response["semanticHitCount"], @"0");
 }

meilisearch/tests/search/mod.rs

@@ -921,7 +921,7 @@ async fn test_score_details() {
                         "order": 3,
                         "attributeRankingOrderScore": 1.0,
                         "queryWordDistanceScore": 0.8095238095238095,
-                        "score": 0.9727891156462584
+                        "score": 0.8095238095238095
                       },
                       "exactness": {
                         "order": 4,

meilisearch/tests/search/restrict_searchable.rs

@@ -285,10 +285,10 @@ async fn attributes_ranking_rule_order() {
                 @r###"
             [
               {
-                "id": "2"
+                "id": "1"
               },
               {
-                "id": "1"
+                "id": "2"
               }
             ]
             "###

meilisearch/tests/snapshot/mod.rs

@@ -1,6 +1,5 @@
 use std::time::Duration;
 
-use actix_rt::time::sleep;
 use meili_snap::{json_string, snapshot};
 use meilisearch::option::ScheduleSnapshot;
 use meilisearch::Opt;
@@ -53,11 +52,29 @@ async fn perform_snapshot() {
 
     index.load_test_set().await;
 
-    server.index("test1").create(Some("prim")).await;
+    let (task, code) = server.index("test1").create(Some("prim")).await;
+    meili_snap::snapshot!(code, @"202 Accepted");
 
-    index.wait_task(2).await;
+    index.wait_task(task.uid()).await;
 
-    sleep(Duration::from_secs(2)).await;
+    // wait for the _next task_ to process, aka the snapshot that should be enqueued at some point
+
+    println!("waited for the next task to finish");
+    let now = std::time::Instant::now();
+    let next_task = task.uid() + 1;
+    loop {
+        let (value, code) = index.get_task(next_task).await;
+        dbg!(&value);
+        if code != 404 && value["status"].as_str() == Some("succeeded") {
+            break;
+        }
+
+        if now.elapsed() > Duration::from_secs(30) {
+            panic!("The snapshot didn't schedule in 30s even though it was supposed to be scheduled every 2s: {}",
+                serde_json::to_string_pretty(&value).unwrap()
+            );
+        }
+    }
 
     let temp = tempfile::tempdir().unwrap();
 

milli/examples/search.rs

@@ -48,7 +48,7 @@ fn main() -> Result<(), Box<dyn Error>> {
 
             let start = Instant::now();
 
-            let mut ctx = SearchContext::new(&index, &txn);
+            let mut ctx = SearchContext::new(&index, &txn)?;
             let universe = filtered_universe(&ctx, &None)?;
 
             let docs = execute_search(

milli/src/error.rs

@@ -32,6 +32,8 @@ pub enum InternalError {
     DatabaseClosing,
     #[error("Missing {} in the {db_name} database.", key.unwrap_or("key"))]
     DatabaseMissingEntry { db_name: &'static str, key: Option<&'static str> },
+    #[error("Missing {key} in the fieldids weights mapping.")]
+    FieldidsWeightsMapMissingEntry { key: FieldId },
     #[error(transparent)]
     FieldIdMapMissingEntry(#[from] FieldIdMapMissingEntry),
     #[error("Missing {key} in the field id mapping.")]

milli/src/fieldids_weights_map.rs

@@ -0,0 +1,48 @@
+//! The fieldids weights map is in charge of storing linking the searchable fields with their weights.
+
+use std::collections::HashMap;
+
+use serde::{Deserialize, Serialize};
+
+use crate::{FieldId, FieldsIdsMap, Weight};
+
+#[derive(Debug, Default, Serialize, Deserialize)]
+pub struct FieldidsWeightsMap {
+    map: HashMap<FieldId, Weight>,
+}
+
+impl FieldidsWeightsMap {
+    /// Insert a field id -> weigth into the map.
+    /// If the map did not have this key present, `None` is returned.
+    /// If the map did have this key present, the value is updated, and the old value is returned.
+    pub fn insert(&mut self, fid: FieldId, weight: Weight) -> Option<Weight> {
+        self.map.insert(fid, weight)
+    }
+
+    /// Create the map from the fields ids maps.
+    /// Should only be called in the case there are NO searchable attributes.
+    /// All the fields will be inserted in the order of the fields ids map with a weight of 0.
+    pub fn from_field_id_map_without_searchable(fid_map: &FieldsIdsMap) -> Self {
+        FieldidsWeightsMap { map: fid_map.ids().map(|fid| (fid, 0)).collect() }
+    }
+
+    /// Removes a field id from the map, returning the associated weight previously in the map.
+    pub fn remove(&mut self, fid: FieldId) -> Option<Weight> {
+        self.map.remove(&fid)
+    }
+
+    /// Returns weight corresponding to the key.
+    pub fn weight(&self, fid: FieldId) -> Option<Weight> {
+        self.map.get(&fid).copied()
+    }
+
+    /// Returns highest weight contained in the map if any.
+    pub fn max_weight(&self) -> Option<Weight> {
+        self.map.values().copied().max()
+    }
+
+    /// Return an iterator visiting all field ids in arbitrary order.
+    pub fn ids(&self) -> impl Iterator<Item = FieldId> + '_ {
+        self.map.keys().copied()
+    }
+}

milli/src/index.rs

@@ -1,5 +1,6 @@
 use std::borrow::Cow;
 use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
+use std::convert::TryInto;
 use std::fs::File;
 use std::path::Path;
 
@@ -25,8 +26,9 @@ use crate::proximity::ProximityPrecision;
 use crate::vector::EmbeddingConfig;
 use crate::{
     default_criteria, CboRoaringBitmapCodec, Criterion, DocumentId, ExternalDocumentsIds,
-    FacetDistribution, FieldDistribution, FieldId, FieldIdWordCountCodec, GeoPoint, ObkvCodec,
+    FacetDistribution, FieldDistribution, FieldId, FieldIdMapMissingEntry, FieldIdWordCountCodec,
-    Result, RoaringBitmapCodec, RoaringBitmapLenCodec, Search, U8StrStrCodec, BEU16, BEU32, BEU64,
+    FieldidsWeightsMap, GeoPoint, ObkvCodec, Result, RoaringBitmapCodec, RoaringBitmapLenCodec,
+    Search, U8StrStrCodec, Weight, BEU16, BEU32, BEU64,
 };
 
 pub const DEFAULT_MIN_WORD_LEN_ONE_TYPO: u8 = 5;
@@ -42,6 +44,7 @@ pub mod main_key {
     pub const SORTABLE_FIELDS_KEY: &str = "sortable-fields";
     pub const FIELD_DISTRIBUTION_KEY: &str = "fields-distribution";
     pub const FIELDS_IDS_MAP_KEY: &str = "fields-ids-map";
+    pub const FIELDIDS_WEIGHTS_MAP_KEY: &str = "fieldids-weights-map";
     pub const GEO_FACETED_DOCUMENTS_IDS_KEY: &str = "geo-faceted-documents-ids";
     pub const GEO_RTREE_KEY: &str = "geo-rtree";
     pub const PRIMARY_KEY_KEY: &str = "primary-key";
@@ -414,6 +417,65 @@ impl Index {
             .unwrap_or_default())
     }
 
+    /* fieldids weights map */
+    // This maps the fields ids to their weights.
+    // Their weights is defined by the ordering of the searchable attributes.
+
+    /// Writes the fieldids weights map which associates the field ids to their weights
+    pub(crate) fn put_fieldids_weights_map(
+        &self,
+        wtxn: &mut RwTxn,
+        map: &FieldidsWeightsMap,
+    ) -> heed::Result<()> {
+        self.main.remap_types::<Str, SerdeJson<_>>().put(
+            wtxn,
+            main_key::FIELDIDS_WEIGHTS_MAP_KEY,
+            map,
+        )
+    }
+
+    /// Get the fieldids weights map which associates the field ids to their weights
+    pub fn fieldids_weights_map(&self, rtxn: &RoTxn) -> heed::Result<FieldidsWeightsMap> {
+        self.main
+            .remap_types::<Str, SerdeJson<_>>()
+            .get(rtxn, main_key::FIELDIDS_WEIGHTS_MAP_KEY)?
+            .map(Ok)
+            .unwrap_or_else(|| {
+                Ok(FieldidsWeightsMap::from_field_id_map_without_searchable(
+                    &self.fields_ids_map(rtxn)?,
+                ))
+            })
+    }
+
+    /// Delete the fieldsids weights map
+    pub fn delete_fieldids_weights_map(&self, wtxn: &mut RwTxn) -> heed::Result<bool> {
+        self.main.remap_key_type::<Str>().delete(wtxn, main_key::FIELDIDS_WEIGHTS_MAP_KEY)
+    }
+
+    pub fn searchable_fields_and_weights<'a>(
+        &self,
+        rtxn: &'a RoTxn,
+    ) -> Result<Vec<(Cow<'a, str>, FieldId, Weight)>> {
+        let fid_map = self.fields_ids_map(rtxn)?;
+        let weight_map = self.fieldids_weights_map(rtxn)?;
+        let searchable = self.searchable_fields(rtxn)?;
+
+        searchable
+            .into_iter()
+            .map(|field| -> Result<_> {
+                let fid = fid_map.id(&field).ok_or_else(|| FieldIdMapMissingEntry::FieldName {
+                    field_name: field.to_string(),
+                    process: "searchable_fields_and_weights",
+                })?;
+                let weight = weight_map
+                    .weight(fid)
+                    .ok_or(InternalError::FieldidsWeightsMapMissingEntry { key: fid })?;
+
+                Ok((field, fid, weight))
+            })
+            .collect()
+    }
+
     /* geo rtree */
 
     /// Writes the provided `rtree` which associates coordinates to documents ids.
@@ -578,33 +640,42 @@ impl Index {
         wtxn: &mut RwTxn,
         user_fields: &[&str],
         fields_ids_map: &FieldsIdsMap,
-    ) -> heed::Result<()> {
+    ) -> Result<()> {
         // We can write the user defined searchable fields as-is.
         self.put_user_defined_searchable_fields(wtxn, user_fields)?;
 
+        let mut weights = FieldidsWeightsMap::default();
+
         // Now we generate the real searchable fields:
         // 1. Take the user defined searchable fields as-is to keep the priority defined by the attributes criterion.
         // 2. Iterate over the user defined searchable fields.
         // 3. If a user defined field is a subset of a field defined in the fields_ids_map
-        // (ie doggo.name is a subset of doggo) then we push it at the end of the fields.
+        // (ie doggo.name is a subset of doggo) right after doggo and with the same weight.
-        let mut real_fields = user_fields.to_vec();
+        let mut real_fields = Vec::new();
 
-        for field_from_map in fields_ids_map.names() {
+        for (id, field_from_map) in fields_ids_map.iter() {
-            for user_field in user_fields {
+            for (weight, user_field) in user_fields.iter().enumerate() {
                 if crate::is_faceted_by(field_from_map, user_field)
-                    && !user_fields.contains(&field_from_map)
+                    && !real_fields.contains(&field_from_map)
                 {
                     real_fields.push(field_from_map);
+
+                    let weight: u16 =
+                        weight.try_into().map_err(|_| UserError::AttributeLimitReached)?;
+                    weights.insert(id, weight);
                 }
             }
         }
 
-        self.put_searchable_fields(wtxn, &real_fields)
+        self.put_searchable_fields(wtxn, &real_fields)?;
+        self.put_fieldids_weights_map(wtxn, &weights)?;
+        Ok(())
     }
 
     pub(crate) fn delete_all_searchable_fields(&self, wtxn: &mut RwTxn) -> heed::Result<bool> {
         let did_delete_searchable = self.delete_searchable_fields(wtxn)?;
         let did_delete_user_defined = self.delete_user_defined_searchable_fields(wtxn)?;
+        self.delete_fieldids_weights_map(wtxn)?;
         Ok(did_delete_searchable || did_delete_user_defined)
     }
 
@@ -623,28 +694,31 @@ impl Index {
     }
 
     /// Returns the searchable fields, those are the fields that are indexed,
-    /// if the searchable fields aren't there it means that **all** the fields are indexed.
+    pub fn searchable_fields<'t>(&self, rtxn: &'t RoTxn) -> heed::Result<Vec<Cow<'t, str>>> {
-    pub fn searchable_fields<'t>(&self, rtxn: &'t RoTxn) -> heed::Result<Option<Vec<&'t str>>> {
         self.main
             .remap_types::<Str, SerdeBincode<Vec<&'t str>>>()
-            .get(rtxn, main_key::SEARCHABLE_FIELDS_KEY)
+            .get(rtxn, main_key::SEARCHABLE_FIELDS_KEY)?
+            .map(|fields| Ok(fields.into_iter().map(Cow::Borrowed).collect()))
+            .unwrap_or_else(|| {
+                Ok(self
+                    .fields_ids_map(rtxn)?
+                    .names()
+                    .map(|field| Cow::Owned(field.to_string()))
+                    .collect())
+            })
     }
 
     /// Identical to `searchable_fields`, but returns the ids instead.
-    pub fn searchable_fields_ids(&self, rtxn: &RoTxn) -> Result<Option<Vec<FieldId>>> {
+    pub fn searchable_fields_ids(&self, rtxn: &RoTxn) -> Result<Vec<FieldId>> {
-        match self.searchable_fields(rtxn)? {
+        let fields = self.searchable_fields(rtxn)?;
-            Some(fields) => {
+        let fields_ids_map = self.fields_ids_map(rtxn)?;
-                let fields_ids_map = self.fields_ids_map(rtxn)?;
+        let mut fields_ids = Vec::new();
-                let mut fields_ids = Vec::new();
+        for name in fields {
-                for name in fields {
+            if let Some(field_id) = fields_ids_map.id(&name) {
-                    if let Some(field_id) = fields_ids_map.id(name) {
+                fields_ids.push(field_id);
-                        fields_ids.push(field_id);
-                    }
-                }
-                Ok(Some(fields_ids))
             }
-            None => Ok(None),
         }
+        Ok(fields_ids)
     }
 
     /// Writes the searchable fields, when this list is specified, only these are indexed.
@@ -1710,10 +1784,14 @@ pub(crate) mod tests {
             ]))
             .unwrap();
 
-        db_snap!(index, field_distribution, 1);
+        db_snap!(index, field_distribution, @r###"
+        age              1      |
+        id               2      |
+        name             2      |
+        "###);
 
         db_snap!(index, word_docids,
-            @r###"
+        @r###"
         1                [0, ]
         2                [1, ]
         20               [1, ]
@@ -1722,18 +1800,6 @@ pub(crate) mod tests {
         "###
         );
 
-        db_snap!(index, field_distribution);
-
-        db_snap!(index, field_distribution,
-            @r###"
-        age              1      |
-        id               2      |
-        name             2      |
-        "###
-        );
-
-        // snapshot_index!(&index, "1", include: "^field_distribution$");
-
         // we add all the documents a second time. we are supposed to get the same
         // field_distribution in the end
         index
@@ -1820,7 +1886,7 @@ pub(crate) mod tests {
         // ensure we get the right real searchable fields + user defined searchable fields
         let rtxn = index.read_txn().unwrap();
 
-        let real = index.searchable_fields(&rtxn).unwrap().unwrap();
+        let real = index.searchable_fields(&rtxn).unwrap();
         assert_eq!(real, &["doggo", "name", "doggo.name", "doggo.age"]);
 
         let user_defined = index.user_defined_searchable_fields(&rtxn).unwrap().unwrap();
@@ -1840,7 +1906,7 @@ pub(crate) mod tests {
         // ensure we get the right real searchable fields + user defined searchable fields
         let rtxn = index.read_txn().unwrap();
 
-        let real = index.searchable_fields(&rtxn).unwrap().unwrap();
+        let real = index.searchable_fields(&rtxn).unwrap();
         assert_eq!(real, &["doggo", "name"]);
         let user_defined = index.user_defined_searchable_fields(&rtxn).unwrap().unwrap();
         assert_eq!(user_defined, &["doggo", "name"]);
@@ -1856,7 +1922,7 @@ pub(crate) mod tests {
         // ensure we get the right real searchable fields + user defined searchable fields
         let rtxn = index.read_txn().unwrap();
 
-        let real = index.searchable_fields(&rtxn).unwrap().unwrap();
+        let real = index.searchable_fields(&rtxn).unwrap();
         assert_eq!(real, &["doggo", "name", "doggo.name", "doggo.age"]);
 
         let user_defined = index.user_defined_searchable_fields(&rtxn).unwrap().unwrap();
@@ -2395,6 +2461,14 @@ pub(crate) mod tests {
         11                       0
         4                        1
         "###);
+        db_snap!(index, fields_ids_map, @r###"
+        0   primary_key      |
+        "###);
+        db_snap!(index, searchable_fields, @r###"["primary_key"]"###);
+        db_snap!(index, fieldids_weights_map, @r###"
+        fid weight
+        0   0   |
+        "###);
 
         index
             .add_documents(documents!([
@@ -2410,6 +2484,16 @@ pub(crate) mod tests {
         11                       0
         4                        1
         "###);
+        db_snap!(index, fields_ids_map, @r###"
+        0   primary_key      |
+        1   a                |
+        "###);
+        db_snap!(index, searchable_fields, @r###"["primary_key", "a"]"###);
+        db_snap!(index, fieldids_weights_map, @r###"
+        fid weight
+        0   0   |
+        1   0   |
+        "###);
 
         index.delete_documents(Default::default());
 
@@ -2420,6 +2504,16 @@ pub(crate) mod tests {
         11                       0
         4                        1
         "###);
+        db_snap!(index, fields_ids_map, @r###"
+        0   primary_key      |
+        1   a                |
+        "###);
+        db_snap!(index, searchable_fields, @r###"["primary_key", "a"]"###);
+        db_snap!(index, fieldids_weights_map, @r###"
+        fid weight
+        0   0   |
+        1   0   |
+        "###);
 
         index
             .add_documents(documents!([
@@ -2435,6 +2529,16 @@ pub(crate) mod tests {
         11                       0
         4                        1
         "###);
+        db_snap!(index, fields_ids_map, @r###"
+        0   primary_key      |
+        1   a                |
+        "###);
+        db_snap!(index, searchable_fields, @r###"["primary_key", "a"]"###);
+        db_snap!(index, fieldids_weights_map, @r###"
+        fid weight
+        0   0   |
+        1   0   |
+        "###);
 
         let rtxn = index.read_txn().unwrap();
         let search = Search::new(&rtxn, &index);
@@ -2520,4 +2624,104 @@ pub(crate) mod tests {
 
         db_snap!(index, geo_faceted_documents_ids); // ensure that no documents were inserted
     }
+
+    #[test]
+    fn swapping_searchable_attributes() {
+        // See https://github.com/meilisearch/meilisearch/issues/4484
+
+        let index = TempIndex::new();
+
+        index
+            .update_settings(|settings| {
+                settings.set_searchable_fields(vec![S("name")]);
+                settings.set_filterable_fields(HashSet::from([S("age")]));
+            })
+            .unwrap();
+
+        index
+            .add_documents(documents!({ "id": 1, "name": "Many", "age": 28, "realName": "Maxime" }))
+            .unwrap();
+        db_snap!(index, fields_ids_map, @r###"
+        0   name             |
+        1   id               |
+        2   age              |
+        3   realName         |
+        "###);
+        db_snap!(index, searchable_fields, @r###"["name"]"###);
+        db_snap!(index, fieldids_weights_map, @r###"
+        fid weight
+        0   0   |
+        "###);
+
+        index
+            .update_settings(|settings| {
+                settings.set_searchable_fields(vec![S("name"), S("realName")]);
+                settings.set_filterable_fields(HashSet::from([S("age")]));
+            })
+            .unwrap();
+
+        // The order of the field id map shouldn't change
+        db_snap!(index, fields_ids_map, @r###"
+        0   name             |
+        1   id               |
+        2   age              |
+        3   realName         |
+        "###);
+        db_snap!(index, searchable_fields, @r###"["name", "realName"]"###);
+        db_snap!(index, fieldids_weights_map, @r###"
+        fid weight
+        0   0   |
+        3   1   |
+        "###);
+    }
+
+    #[test]
+    fn attribute_weights_after_swapping_searchable_attributes() {
+        // See https://github.com/meilisearch/meilisearch/issues/4484
+
+        let index = TempIndex::new();
+
+        index
+            .update_settings(|settings| {
+                settings.set_searchable_fields(vec![S("name"), S("beverage")]);
+            })
+            .unwrap();
+
+        index
+            .add_documents(documents!([
+                { "id": 0, "name": "kefir", "beverage": "water" },
+                { "id": 1, "name": "tamo",  "beverage": "kefir" }
+            ]))
+            .unwrap();
+
+        let rtxn = index.read_txn().unwrap();
+        let mut search = index.search(&rtxn);
+        let results = search.query("kefir").execute().unwrap();
+
+        // We should find kefir the dog first
+        insta::assert_debug_snapshot!(results.documents_ids, @r###"
+        [
+            0,
+            1,
+        ]
+        "###);
+
+        index
+            .update_settings(|settings| {
+                settings.set_searchable_fields(vec![S("beverage"), S("name")]);
+            })
+            .unwrap();
+
+        let rtxn = index.read_txn().unwrap();
+        let mut search = index.search(&rtxn);
+        let results = search.query("kefir").execute().unwrap();
+
+        // We should find tamo first
+        insta::assert_debug_snapshot!(results.documents_ids, @r###"
+        [
+            1,
+            0,
+        ]
+        "###);
+    }
 }

milli/src/lib.rs

@@ -28,6 +28,7 @@ pub mod vector;
 #[cfg(test)]
 #[macro_use]
 pub mod snapshot_tests;
+mod fieldids_weights_map;
 
 use std::collections::{BTreeMap, HashMap};
 use std::convert::{TryFrom, TryInto};
@@ -52,6 +53,7 @@ pub use self::error::{
     Error, FieldIdMapMissingEntry, InternalError, SerializationError, UserError,
 };
 pub use self::external_documents_ids::ExternalDocumentsIds;
+pub use self::fieldids_weights_map::FieldidsWeightsMap;
 pub use self::fields_ids_map::FieldsIdsMap;
 pub use self::heed_codec::{
     BEU16StrCodec, BEU32StrCodec, BoRoaringBitmapCodec, BoRoaringBitmapLenCodec,
@@ -77,6 +79,7 @@ pub type FastMap4<K, V> = HashMap<K, V, BuildHasherDefault<FxHasher32>>;
 pub type FastMap8<K, V> = HashMap<K, V, BuildHasherDefault<FxHasher64>>;
 pub type FieldDistribution = BTreeMap<String, u64>;
 pub type FieldId = u16;
+pub type Weight = u16;
 pub type Object = serde_json::Map<String, serde_json::Value>;
 pub type Position = u32;
 pub type RelativePosition = u16;

milli/src/search/mod.rs

@@ -147,7 +147,7 @@ impl<'a> Search<'a> {
 
     pub fn execute_for_candidates(&self, has_vector_search: bool) -> Result<RoaringBitmap> {
         if has_vector_search {
-            let ctx = SearchContext::new(self.index, self.rtxn);
+            let ctx = SearchContext::new(self.index, self.rtxn)?;
             filtered_universe(&ctx, &self.filter)
         } else {
             Ok(self.execute()?.candidates)
@@ -155,10 +155,10 @@ impl<'a> Search<'a> {
     }
 
     pub fn execute(&self) -> Result<SearchResult> {
-        let mut ctx = SearchContext::new(self.index, self.rtxn);
+        let mut ctx = SearchContext::new(self.index, self.rtxn)?;
 
         if let Some(searchable_attributes) = self.searchable_attributes {
-            ctx.searchable_attributes(searchable_attributes)?;
+            ctx.attributes_to_search_on(searchable_attributes)?;
         }
 
         let universe = filtered_universe(&ctx, &self.filter)?;

milli/src/search/new/bucket_sort.rs

@@ -101,7 +101,7 @@ pub fn bucket_sort<'ctx, Q: RankingRuleQueryTrait>(
 
     let mut ranking_rule_universes: Vec<RoaringBitmap> =
         vec![RoaringBitmap::default(); ranking_rules_len];
-    ranking_rule_universes[0] = universe.clone();
+    ranking_rule_universes[0].clone_from(universe);
     let mut cur_ranking_rule_index = 0;
 
     /// Finish iterating over the current ranking rule, yielding
@@ -232,7 +232,7 @@ pub fn bucket_sort<'ctx, Q: RankingRuleQueryTrait>(
         }
 
         cur_ranking_rule_index += 1;
-        ranking_rule_universes[cur_ranking_rule_index] = next_bucket.candidates.clone();
+        ranking_rule_universes[cur_ranking_rule_index].clone_from(&next_bucket.candidates);
         logger.start_iteration_ranking_rule(
             cur_ranking_rule_index,
             ranking_rules[cur_ranking_rule_index].as_ref(),

milli/src/search/new/db_cache.rs

@@ -163,7 +163,7 @@ impl<'ctx> SearchContext<'ctx> {
             Some(restricted_fids) => {
                 let interned = self.word_interner.get(word).as_str();
                 let keys: Vec<_> =
-                    restricted_fids.tolerant.iter().map(|fid| (interned, *fid)).collect();
+                    restricted_fids.tolerant.iter().map(|(fid, _)| (interned, *fid)).collect();
 
                 DatabaseCache::get_value_from_keys::<_, _, CboRoaringBitmapCodec>(
                     self.txn,
@@ -192,7 +192,7 @@ impl<'ctx> SearchContext<'ctx> {
             Some(restricted_fids) => {
                 let interned = self.word_interner.get(word).as_str();
                 let keys: Vec<_> =
-                    restricted_fids.exact.iter().map(|fid| (interned, *fid)).collect();
+                    restricted_fids.exact.iter().map(|(fid, _)| (interned, *fid)).collect();
 
                 DatabaseCache::get_value_from_keys::<_, _, CboRoaringBitmapCodec>(
                     self.txn,
@@ -242,7 +242,7 @@ impl<'ctx> SearchContext<'ctx> {
             Some(restricted_fids) => {
                 let interned = self.word_interner.get(prefix).as_str();
                 let keys: Vec<_> =
-                    restricted_fids.tolerant.iter().map(|fid| (interned, *fid)).collect();
+                    restricted_fids.tolerant.iter().map(|(fid, _)| (interned, *fid)).collect();
 
                 DatabaseCache::get_value_from_keys::<_, _, CboRoaringBitmapCodec>(
                     self.txn,
@@ -271,7 +271,7 @@ impl<'ctx> SearchContext<'ctx> {
             Some(restricted_fids) => {
                 let interned = self.word_interner.get(prefix).as_str();
                 let keys: Vec<_> =
-                    restricted_fids.exact.iter().map(|fid| (interned, *fid)).collect();
+                    restricted_fids.exact.iter().map(|(fid, _)| (interned, *fid)).collect();
 
                 DatabaseCache::get_value_from_keys::<_, _, CboRoaringBitmapCodec>(
                     self.txn,
@@ -315,11 +315,7 @@ impl<'ctx> SearchContext<'ctx> {
                         .map_err(heed::Error::Decoding)?
                 } else {
                     // Compute the distance at the attribute level and store it in the cache.
-                    let fids = if let Some(fids) = self.index.searchable_fields_ids(self.txn)? {
+                    let fids = self.index.searchable_fields_ids(self.txn)?;
-                        fids
-                    } else {
-                        self.index.fields_ids_map(self.txn)?.ids().collect()
-                    };
                     let mut docids = RoaringBitmap::new();
                     for fid in fids {
                         // for each field, intersect left word bitmap and right word bitmap,
@@ -408,11 +404,7 @@ impl<'ctx> SearchContext<'ctx> {
             let prefix_docids = match proximity_precision {
                 ProximityPrecision::ByAttribute => {
                     // Compute the distance at the attribute level and store it in the cache.
-                    let fids = if let Some(fids) = self.index.searchable_fields_ids(self.txn)? {
+                    let fids = self.index.searchable_fields_ids(self.txn)?;
-                        fids
-                    } else {
-                        self.index.fields_ids_map(self.txn)?.ids().collect()
-                    };
                     let mut prefix_docids = RoaringBitmap::new();
                     // for each field, intersect left word bitmap and right word bitmap,
                     // then merge the result in a global bitmap before storing it in the cache.

milli/src/search/new/exact_attribute.rs

@@ -184,13 +184,7 @@ impl State {
             return Ok(State::Empty(query_graph.clone()));
         }
 
-        let searchable_fields_ids = {
+        let searchable_fields_ids = ctx.index.searchable_fields_ids(ctx.txn)?;
-            if let Some(fids) = ctx.index.searchable_fields_ids(ctx.txn)? {
-                fids
-            } else {
-                ctx.index.fields_ids_map(ctx.txn)?.ids().collect()
-            }
-        };
 
         let mut candidates_per_attribute = Vec::with_capacity(searchable_fields_ids.len());
         // then check that there exists at least one attribute that has all of the terms

milli/src/search/new/matches/matching_words.rs

@@ -258,7 +258,7 @@ pub(crate) mod tests {
     fn matching_words() {
         let temp_index = temp_index_with_documents();
         let rtxn = temp_index.read_txn().unwrap();
-        let mut ctx = SearchContext::new(&temp_index, &rtxn);
+        let mut ctx = SearchContext::new(&temp_index, &rtxn).unwrap();
         let mut builder = TokenizerBuilder::default();
         let tokenizer = builder.build();
         let tokens = tokenizer.tokenize("split this world");

milli/src/search/new/matches/mod.rs

@@ -506,7 +506,7 @@ mod tests {
 
     impl<'a> MatcherBuilder<'a> {
         fn new_test(rtxn: &'a heed::RoTxn, index: &'a TempIndex, query: &str) -> Self {
-            let mut ctx = SearchContext::new(index, rtxn);
+            let mut ctx = SearchContext::new(index, rtxn).unwrap();
             let universe = filtered_universe(&ctx, &None).unwrap();
             let crate::search::PartialSearchResult { located_query_terms, .. } = execute_search(
                 &mut ctx,

milli/src/search/new/mod.rs

@@ -49,13 +49,12 @@ pub use self::geo_sort::Strategy as GeoSortStrategy;
 use self::graph_based_ranking_rule::Words;
 use self::interner::Interned;
 use self::vector_sort::VectorSort;
-use crate::error::FieldIdMapMissingEntry;
 use crate::score_details::{ScoreDetails, ScoringStrategy};
 use crate::search::new::distinct::apply_distinct_rule;
 use crate::vector::Embedder;
 use crate::{
     AscDesc, DocumentId, FieldId, Filter, Index, Member, Result, TermsMatchingStrategy, TimeBudget,
-    UserError,
+    UserError, Weight,
 };
 
 /// A structure used throughout the execution of a search query.
@@ -71,8 +70,21 @@ pub struct SearchContext<'ctx> {
 }
 
 impl<'ctx> SearchContext<'ctx> {
-    pub fn new(index: &'ctx Index, txn: &'ctx RoTxn<'ctx>) -> Self {
+    pub fn new(index: &'ctx Index, txn: &'ctx RoTxn<'ctx>) -> Result<Self> {
-        Self {
+        let searchable_fids = index.searchable_fields_and_weights(txn)?;
+        let exact_attributes_ids = index.exact_attributes_ids(txn)?;
+
+        let mut exact = Vec::new();
+        let mut tolerant = Vec::new();
+        for (_name, fid, weight) in searchable_fids {
+            if exact_attributes_ids.contains(&fid) {
+                exact.push((fid, weight));
+            } else {
+                tolerant.push((fid, weight));
+            }
+        }
+
+        Ok(Self {
             index,
             txn,
             db_cache: <_>::default(),
@@ -81,42 +93,39 @@ impl<'ctx> SearchContext<'ctx> {
             term_interner: <_>::default(),
             phrase_docids: <_>::default(),
             restricted_fids: None,
-        }
+        })
     }
 
-    pub fn searchable_attributes(&mut self, searchable_attributes: &'ctx [String]) -> Result<()> {
+    pub fn attributes_to_search_on(
-        let fids_map = self.index.fields_ids_map(self.txn)?;
+        &mut self,
-        let searchable_names = self.index.searchable_fields(self.txn)?;
+        attributes_to_search_on: &'ctx [String],
+    ) -> Result<()> {
+        let user_defined_searchable = self.index.user_defined_searchable_fields(self.txn)?;
+        let searchable_fields_weights = self.index.searchable_fields_and_weights(self.txn)?;
         let exact_attributes_ids = self.index.exact_attributes_ids(self.txn)?;
 
+        let mut wildcard = false;
+
         let mut restricted_fids = RestrictedFids::default();
-        let mut contains_wildcard = false;
+        for field_name in attributes_to_search_on {
-        for field_name in searchable_attributes {
             if field_name == "*" {
-                contains_wildcard = true;
+                wildcard = true;
+                // we cannot early exit as we want to returns error in case of unknown fields
                 continue;
             }
-            let searchable_contains_name =
+            let searchable_weight =
-                searchable_names.as_ref().map(|sn| sn.iter().any(|name| name == field_name));
+                searchable_fields_weights.iter().find(|(name, _, _)| name == field_name);
-            let fid = match (fids_map.id(field_name), searchable_contains_name) {
+            let (fid, weight) = match searchable_weight {
                 // The Field id exist and the field is searchable
-                (Some(fid), Some(true)) | (Some(fid), None) => fid,
+                Some((_name, fid, weight)) => (*fid, *weight),
-                // The field is searchable but the Field id doesn't exist => Internal Error
+                // The field is not searchable but the user didn't define any searchable attributes
-                (None, Some(true)) => {
+                None if user_defined_searchable.is_none() => continue,
-                    return Err(FieldIdMapMissingEntry::FieldName {
-                        field_name: field_name.to_string(),
-                        process: "search",
-                    }
-                    .into())
-                }
-                // The field is not searchable, but the searchableAttributes are set to * => ignore field
-                (None, None) => continue,
                 // The field is not searchable => User error
-                (_fid, Some(false)) => {
+                None => {
-                    let (valid_fields, hidden_fields) = match searchable_names {
+                    let (valid_fields, hidden_fields) = self.index.remove_hidden_fields(
-                        Some(sn) => self.index.remove_hidden_fields(self.txn, sn)?,
+                        self.txn,
-                        None => self.index.remove_hidden_fields(self.txn, fids_map.names())?,
+                        searchable_fields_weights.iter().map(|(name, _, _)| name),
-                    };
+                    )?;
 
                     let field = field_name.to_string();
                     return Err(UserError::InvalidSearchableAttribute {
@@ -129,13 +138,17 @@ impl<'ctx> SearchContext<'ctx> {
             };
 
             if exact_attributes_ids.contains(&fid) {
-                restricted_fids.exact.push(fid);
+                restricted_fids.exact.push((fid, weight));
             } else {
-                restricted_fids.tolerant.push(fid);
+                restricted_fids.tolerant.push((fid, weight));
             };
         }
 
-        self.restricted_fids = (!contains_wildcard).then_some(restricted_fids);
+        if wildcard {
+            self.restricted_fids = None;
+        } else {
+            self.restricted_fids = Some(restricted_fids);
+        }
 
         Ok(())
     }
@@ -158,13 +171,13 @@ impl Word {
 
 #[derive(Debug, Clone, Default)]
 pub struct RestrictedFids {
-    pub tolerant: Vec<FieldId>,
+    pub tolerant: Vec<(FieldId, Weight)>,
-    pub exact: Vec<FieldId>,
+    pub exact: Vec<(FieldId, Weight)>,
 }
 
 impl RestrictedFids {
     pub fn contains(&self, fid: &FieldId) -> bool {
-        self.tolerant.contains(fid) || self.exact.contains(fid)
+        self.tolerant.iter().any(|(id, _)| id == fid) || self.exact.iter().any(|(id, _)| id == fid)
     }
 }
 

milli/src/search/new/query_term/parse_query.rs

@@ -366,7 +366,7 @@ mod tests {
         let tokens = tokenizer.tokenize(".");
         let index = temp_index_with_documents();
         let rtxn = index.read_txn()?;
-        let mut ctx = SearchContext::new(&index, &rtxn);
+        let mut ctx = SearchContext::new(&index, &rtxn)?;
         // panics with `attempt to add with overflow` before <https://github.com/meilisearch/meilisearch/issues/3785>
         let ExtractedTokens { query_terms, .. } =
             located_query_terms_from_tokens(&mut ctx, tokens, None)?;

milli/src/search/new/ranking_rule_graph/fid/mod.rs

@@ -7,12 +7,12 @@ use crate::search::new::interner::{DedupInterner, Interned};
 use crate::search::new::query_term::LocatedQueryTermSubset;
 use crate::search::new::resolve_query_graph::compute_query_term_subset_docids_within_field_id;
 use crate::search::new::SearchContext;
-use crate::Result;
+use crate::{FieldId, InternalError, Result};
 
 #[derive(Clone, PartialEq, Eq, Hash)]
 pub struct FidCondition {
     term: LocatedQueryTermSubset,
-    fid: u16,
+    fid: Option<FieldId>,
 }
 
 pub enum FidGraph {}
@@ -26,13 +26,15 @@ impl RankingRuleGraphTrait for FidGraph {
         universe: &RoaringBitmap,
     ) -> Result<ComputedCondition> {
         let FidCondition { term, .. } = condition;
-        // maybe compute_query_term_subset_docids_within_field_id should accept a universe as argument
+
-        let mut docids = compute_query_term_subset_docids_within_field_id(
+        let docids = if let Some(fid) = condition.fid {
-            ctx,
+            // maybe compute_query_term_subset_docids_within_field_id should accept a universe as argument
-            &term.term_subset,
+            let docids =
-            condition.fid,
+                compute_query_term_subset_docids_within_field_id(ctx, &term.term_subset, fid)?;
-        )?;
+            docids & universe
-        docids &= universe;
+        } else {
+            RoaringBitmap::new()
+        };
 
         Ok(ComputedCondition {
             docids,
@@ -68,34 +70,29 @@ impl RankingRuleGraphTrait for FidGraph {
             all_fields.extend(fields);
         }
 
+        let weights_map = ctx.index.fieldids_weights_map(ctx.txn)?;
+
         let mut edges = vec![];
         for fid in all_fields.iter().copied() {
+            let weight = weights_map
+                .weight(fid)
+                .ok_or(InternalError::FieldidsWeightsMapMissingEntry { key: fid })?;
             edges.push((
-                fid as u32 * term.term_ids.len() as u32,
+                weight as u32 * term.term_ids.len() as u32,
-                conditions_interner.insert(FidCondition { term: term.clone(), fid }),
+                conditions_interner.insert(FidCondition { term: term.clone(), fid: Some(fid) }),
             ));
         }
 
         // always lookup the max_fid if we don't already and add an artificial condition for max scoring
-        let max_fid: Option<u16> = {
+        let max_weight: Option<u16> = weights_map.max_weight();
-            if let Some(max_fid) = ctx
-                .index
-                .searchable_fields_ids(ctx.txn)?
-                .map(|field_ids| field_ids.into_iter().max())
-            {
-                max_fid
-            } else {
-                ctx.index.fields_ids_map(ctx.txn)?.ids().max()
-            }
-        };
 
-        if let Some(max_fid) = max_fid {
+        if let Some(max_weight) = max_weight {
-            if !all_fields.contains(&max_fid) {
+            if !all_fields.contains(&max_weight) {
                 edges.push((
-                    max_fid as u32 * term.term_ids.len() as u32, // TODO improve the fid score i.e. fid^10.
+                    max_weight as u32 * term.term_ids.len() as u32, // TODO improve the fid score i.e. fid^10.
                     conditions_interner.insert(FidCondition {
                         term: term.clone(), // TODO remove this ugly clone
-                        fid: max_fid,
+                        fid: None,
                     }),
                 ));
             }

milli/src/search/new/tests/attribute_fid.rs

@@ -1,5 +1,5 @@
 use crate::index::tests::TempIndex;
-use crate::{Criterion, Search, SearchResult, TermsMatchingStrategy};
+use crate::{db_snap, Criterion, Search, SearchResult, TermsMatchingStrategy};
 
 fn create_index() -> TempIndex {
     let index = TempIndex::new();
@@ -131,6 +131,19 @@ fn test_attribute_fid_simple() {
 #[test]
 fn test_attribute_fid_ngrams() {
     let index = create_index();
+    db_snap!(index, fields_ids_map, @r###"
+    0   id               |
+    1   title            |
+    2   description      |
+    3   plot             |
+    "###);
+    db_snap!(index, searchable_fields, @r###"["title", "description", "plot"]"###);
+    db_snap!(index, fieldids_weights_map, @r###"
+    fid weight
+    1   0   |
+    2   1   |
+    3   2   |
+    "###);
 
     let txn = index.read_txn().unwrap();
 

milli/src/search/new/tests/snapshots/milli__search__new__tests__attribute_fid__attribute_fid_ngrams-4.snap

@@ -0,0 +1,244 @@
+---
+source: milli/src/search/new/tests/attribute_fid.rs
+expression: "format!(\"{document_ids_scores:#?}\")"
+---
+[
+    (
+        2,
+        [
+            Fid(
+                Rank {
+                    rank: 19,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 91,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        6,
+        [
+            Fid(
+                Rank {
+                    rank: 15,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 81,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        5,
+        [
+            Fid(
+                Rank {
+                    rank: 14,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 79,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        4,
+        [
+            Fid(
+                Rank {
+                    rank: 13,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 77,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        3,
+        [
+            Fid(
+                Rank {
+                    rank: 12,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 83,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        9,
+        [
+            Fid(
+                Rank {
+                    rank: 11,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 75,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        8,
+        [
+            Fid(
+                Rank {
+                    rank: 10,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 79,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        7,
+        [
+            Fid(
+                Rank {
+                    rank: 10,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 73,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        11,
+        [
+            Fid(
+                Rank {
+                    rank: 7,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 77,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        10,
+        [
+            Fid(
+                Rank {
+                    rank: 6,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 81,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        13,
+        [
+            Fid(
+                Rank {
+                    rank: 6,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 81,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        12,
+        [
+            Fid(
+                Rank {
+                    rank: 6,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 78,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        14,
+        [
+            Fid(
+                Rank {
+                    rank: 5,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 75,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+    (
+        0,
+        [
+            Fid(
+                Rank {
+                    rank: 1,
+                    max_rank: 19,
+                },
+            ),
+            Position(
+                Rank {
+                    rank: 91,
+                    max_rank: 91,
+                },
+            ),
+        ],
+    ),
+]

milli/src/snapshot_tests.rs

@@ -308,6 +308,25 @@ pub fn snap_fields_ids_map(index: &Index) -> String {
     }
     snap
 }
+pub fn snap_fieldids_weights_map(index: &Index) -> String {
+    let rtxn = index.read_txn().unwrap();
+    let weights_map = index.fieldids_weights_map(&rtxn).unwrap();
+
+    let mut snap = String::new();
+    writeln!(&mut snap, "fid weight").unwrap();
+    let mut field_ids: Vec<_> = weights_map.ids().collect();
+    field_ids.sort();
+    for field_id in field_ids {
+        let weight = weights_map.weight(field_id).unwrap();
+        writeln!(&mut snap, "{field_id:<3} {weight:<3} |").unwrap();
+    }
+    snap
+}
+pub fn snap_searchable_fields(index: &Index) -> String {
+    let rtxn = index.read_txn().unwrap();
+    let searchable_fields = index.searchable_fields(&rtxn).unwrap();
+    format!("{searchable_fields:?}")
+}
 pub fn snap_geo_faceted_documents_ids(index: &Index) -> String {
     let rtxn = index.read_txn().unwrap();
     let geo_faceted_documents_ids = index.geo_faceted_documents_ids(&rtxn).unwrap();
@@ -469,6 +488,12 @@ macro_rules! full_snap_of_db {
     ($index:ident, fields_ids_map) => {{
         $crate::snapshot_tests::snap_fields_ids_map(&$index)
     }};
+    ($index:ident, fieldids_weights_map) => {{
+        $crate::snapshot_tests::snap_fieldids_weights_map(&$index)
+    }};
+    ($index:ident, searchable_fields) => {{
+        $crate::snapshot_tests::snap_searchable_fields(&$index)
+    }};
     ($index:ident, geo_faceted_documents_ids) => {{
         $crate::snapshot_tests::snap_geo_faceted_documents_ids(&$index)
     }};

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

@@ -186,7 +186,7 @@ fn searchable_fields_changed(
 ) -> bool {
     let searchable_fields = &settings_diff.new.searchable_fields_ids;
     for (field_id, field_bytes) in obkv.iter() {
-        if searchable_fields.as_ref().map_or(true, |sf| sf.contains(&field_id)) {
+        if searchable_fields.contains(&field_id) {
             let del_add = KvReaderDelAdd::new(field_bytes);
             match (del_add.get(DelAdd::Deletion), del_add.get(DelAdd::Addition)) {
                 // if both fields are None, check the next field.
@@ -298,7 +298,7 @@ fn lang_safe_tokens_from_document<'a>(
 /// Extract words mapped with their positions of a document.
 fn tokens_from_document<'a>(
     obkv: &KvReader<FieldId>,
-    searchable_fields: &Option<Vec<FieldId>>,
+    searchable_fields: &[FieldId],
     tokenizer: &Tokenizer,
     max_positions_per_attributes: u32,
     del_add: DelAdd,
@@ -309,7 +309,7 @@ fn tokens_from_document<'a>(
     let mut document_writer = KvWriterU16::new(&mut buffers.obkv_buffer);
     for (field_id, field_bytes) in obkv.iter() {
         // if field is searchable.
-        if searchable_fields.as_ref().map_or(true, |sf| sf.contains(&field_id)) {
+        if searchable_fields.as_ref().contains(&field_id) {
             // extract deletion or addition only.
             if let Some(field_bytes) = KvReaderDelAdd::new(field_bytes).get(del_add) {
                 // parse json.

milli/src/update/index_documents/mod.rs

@@ -3260,6 +3260,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg(feature = "all-tokenizations")]
     fn stored_detected_script_and_language_should_not_return_deleted_documents() {
         use charabia::{Language, Script};
         let index = TempIndex::new();

milli/src/update/settings.rs

@@ -461,50 +461,39 @@ impl<'a, 't, 'i> Settings<'a, 't, 'i> {
         Ok(true)
     }
 
-    /// Updates the index's searchable attributes. This causes the field map to be recomputed to
+    /// Updates the index's searchable attributes.
-    /// reflect the order of the searchable attributes.
     fn update_searchable(&mut self) -> Result<bool> {
         match self.searchable_fields {
             Setting::Set(ref fields) => {
                 // Check to see if the searchable fields changed before doing anything else
                 let old_fields = self.index.searchable_fields(self.wtxn)?;
-                let did_change = match old_fields {
+                let did_change = {
-                    // If old_fields is Some, let's check to see if the fields actually changed
+                    let new_fields = fields.iter().map(String::as_str).collect::<Vec<_>>();
-                    Some(old_fields) => {
+                    new_fields != old_fields
-                        let new_fields = fields.iter().map(String::as_str).collect::<Vec<_>>();
-                        new_fields != old_fields
-                    }
-                    // If old_fields is None, the fields have changed (because they are being set)
-                    None => true,
                 };
                 if !did_change {
                     return Ok(false);
                 }
 
-                // every time the searchable attributes are updated, we need to update the
+                // Since we're updating the settings we can only add new fields at the end of the field id map
-                // ids for any settings that uses the facets. (distinct_fields, filterable_fields).
+                let mut fields_ids_map = self.index.fields_ids_map(self.wtxn)?;
-                let old_fields_ids_map = self.index.fields_ids_map(self.wtxn)?;
-
-                let mut new_fields_ids_map = FieldsIdsMap::new();
                 // fields are deduplicated, only the first occurrence is taken into account
                 let names = fields.iter().unique().map(String::as_str).collect::<Vec<_>>();
 
                 // Add all the searchable attributes to the field map, and then add the
                 // remaining fields from the old field map to the new one
                 for name in names.iter() {
-                    new_fields_ids_map.insert(name).ok_or(UserError::AttributeLimitReached)?;
+                    // The fields ids map won't change the field id of already present elements thus only the
-                }
+                    // new fields will be inserted.
-
+                    fields_ids_map.insert(name).ok_or(UserError::AttributeLimitReached)?;
-                for (_, name) in old_fields_ids_map.iter() {
-                    new_fields_ids_map.insert(name).ok_or(UserError::AttributeLimitReached)?;
                 }
 
                 self.index.put_all_searchable_fields_from_fields_ids_map(
                     self.wtxn,
                     &names,
-                    &new_fields_ids_map,
+                    &fields_ids_map,
                 )?;
-                self.index.put_fields_ids_map(self.wtxn, &new_fields_ids_map)?;
+                self.index.put_fields_ids_map(self.wtxn, &fields_ids_map)?;
                 Ok(true)
             }
             Setting::Reset => Ok(self.index.delete_all_searchable_fields(self.wtxn)?),
@@ -1172,7 +1161,7 @@ pub(crate) struct InnerIndexSettings {
     pub user_defined_faceted_fields: HashSet<String>,
     pub user_defined_searchable_fields: Option<Vec<String>>,
     pub faceted_fields_ids: HashSet<FieldId>,
-    pub searchable_fields_ids: Option<Vec<FieldId>>,
+    pub searchable_fields_ids: Vec<FieldId>,
     pub exact_attributes: HashSet<FieldId>,
     pub proximity_precision: ProximityPrecision,
     pub embedding_configs: EmbeddingConfigs,
@@ -1233,18 +1222,21 @@ impl InnerIndexSettings {
 
     // find and insert the new field ids
     pub fn recompute_searchables(&mut self, wtxn: &mut heed::RwTxn, index: &Index) -> Result<()> {
+        let searchable_fields = self
+            .user_defined_searchable_fields
+            .as_ref()
+            .map(|searchable| searchable.iter().map(|s| s.as_str()).collect::<Vec<_>>());
+
         // in case new fields were introduced we're going to recreate the searchable fields.
-        if let Some(searchable_fields) = self.user_defined_searchable_fields.as_ref() {
+        if let Some(searchable_fields) = searchable_fields {
-            let searchable_fields =
-                searchable_fields.iter().map(String::as_ref).collect::<Vec<_>>();
             index.put_all_searchable_fields_from_fields_ids_map(
                 wtxn,
                 &searchable_fields,
                 &self.fields_ids_map,
             )?;
-            let searchable_fields_ids = index.searchable_fields_ids(wtxn)?;
-            self.searchable_fields_ids = searchable_fields_ids;
         }
+        let searchable_fields_ids = index.searchable_fields_ids(wtxn)?;
+        self.searchable_fields_ids = searchable_fields_ids;
 
         Ok(())
     }
@@ -1517,12 +1509,13 @@ mod tests {
     use big_s::S;
     use heed::types::Bytes;
     use maplit::{btreemap, btreeset, hashset};
+    use meili_snap::snapshot;
 
     use super::*;
     use crate::error::Error;
     use crate::index::tests::TempIndex;
     use crate::update::ClearDocuments;
-    use crate::{Criterion, Filter, SearchResult};
+    use crate::{db_snap, Criterion, Filter, SearchResult};
 
     #[test]
     fn set_and_reset_searchable_fields() {
@@ -1551,6 +1544,17 @@ mod tests {
 
         wtxn.commit().unwrap();
 
+        db_snap!(index, fields_ids_map, @r###"
+        0   id               |
+        1   name             |
+        2   age              |
+        "###);
+        db_snap!(index, searchable_fields, @r###"["name"]"###);
+        db_snap!(index, fieldids_weights_map, @r###"
+        fid weight
+        1   0   |
+        "###);
+
         // Check that the searchable field is correctly set to "name" only.
         let rtxn = index.read_txn().unwrap();
         // When we search for something that is not in
@@ -1562,8 +1566,9 @@ mod tests {
         // we must find the appropriate document.
         let result = index.search(&rtxn).query(r#""kevin""#).execute().unwrap();
         let documents = index.documents(&rtxn, result.documents_ids).unwrap();
+        let fid_map = index.fields_ids_map(&rtxn).unwrap();
         assert_eq!(documents.len(), 1);
-        assert_eq!(documents[0].1.get(0), Some(&br#""kevin""#[..]));
+        assert_eq!(documents[0].1.get(fid_map.id("name").unwrap()), Some(&br#""kevin""#[..]));
         drop(rtxn);
 
         // We change the searchable fields to be the "name" field only.
@@ -1573,14 +1578,31 @@ mod tests {
             })
             .unwrap();
 
+        db_snap!(index, fields_ids_map, @r###"
+        0   id               |
+        1   name             |
+        2   age              |
+        "###);
+        db_snap!(index, searchable_fields, @r###"["id", "name", "age"]"###);
+        db_snap!(index, fieldids_weights_map, @r###"
+        fid weight
+        0   0   |
+        1   0   |
+        2   0   |
+        "###);
+
         // Check that the searchable field have been reset and documents are found now.
         let rtxn = index.read_txn().unwrap();
+        let fid_map = index.fields_ids_map(&rtxn).unwrap();
+        let user_defined_searchable_fields = index.user_defined_searchable_fields(&rtxn).unwrap();
+        snapshot!(format!("{user_defined_searchable_fields:?}"), @"None");
+        // the searchable fields should contain all the fields
         let searchable_fields = index.searchable_fields(&rtxn).unwrap();
-        assert_eq!(searchable_fields, None);
+        snapshot!(format!("{searchable_fields:?}"), @r###"["id", "name", "age"]"###);
         let result = index.search(&rtxn).query("23").execute().unwrap();
         assert_eq!(result.documents_ids.len(), 1);
         let documents = index.documents(&rtxn, result.documents_ids).unwrap();
-        assert_eq!(documents[0].1.get(0), Some(&br#""kevin""#[..]));
+        assert_eq!(documents[0].1.get(fid_map.id("name").unwrap()), Some(&br#""kevin""#[..]));
     }
 
     #[test]