Move the sortFacetValuesBy in the faceting settings

dump/src/reader/compat/v5_to_v6.rs

@@ -362,6 +362,7 @@ impl<T> From<v5::Settings<T>> for v6::Settings<v6::Unchecked> {
             faceting: match settings.faceting {
                 v5::Setting::Set(faceting) => v6::Setting::Set(v6::FacetingSettings {
                     max_values_per_facet: faceting.max_values_per_facet.into(),
+                    sort_facet_values_by: v6::Setting::NotSet,
                 }),
                 v5::Setting::Reset => v6::Setting::Reset,
                 v5::Setting::NotSet => v6::Setting::NotSet,

meilisearch-types/src/facet_values_sort.rs

@@ -0,0 +1,33 @@
+use deserr::Deserr;
+use milli::OrderBy;
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Default, Copy, Clone, PartialEq, Eq, Serialize, Deserialize, Deserr)]
+#[serde(rename_all = "camelCase")]
+#[deserr(rename_all = camelCase)]
+pub enum FacetValuesSort {
+    /// Facet values are sorted in alphabetical order, ascending from A to Z.
+    #[default]
+    Alpha,
+    /// Facet values are sorted by decreasing count.
+    /// The count is the number of records containing this facet value in the results of the query.
+    Count,
+}
+
+impl From<FacetValuesSort> for OrderBy {
+    fn from(val: FacetValuesSort) -> Self {
+        match val {
+            FacetValuesSort::Alpha => OrderBy::Lexicographic,
+            FacetValuesSort::Count => OrderBy::Count,
+        }
+    }
+}
+
+impl From<OrderBy> for FacetValuesSort {
+    fn from(val: OrderBy) -> Self {
+        match val {
+            OrderBy::Lexicographic => FacetValuesSort::Alpha,
+            OrderBy::Count => FacetValuesSort::Count,
+        }
+    }
+}

meilisearch-types/src/lib.rs

@@ -2,6 +2,7 @@ pub mod compression;
 pub mod deserr;
 pub mod document_formats;
 pub mod error;
+pub mod facet_values_sort;
 pub mod features;
 pub mod index_uid;
 pub mod index_uid_pattern;

meilisearch-types/src/settings.rs

@@ -14,6 +14,7 @@ use serde::{Deserialize, Serialize, Serializer};
 
 use crate::deserr::DeserrJsonError;
 use crate::error::deserr_codes::*;
+use crate::facet_values_sort::FacetValuesSort;
 
 /// The maximimum number of results that the engine
 /// will be able to return in one search call.
@@ -102,6 +103,9 @@ pub struct FacetingSettings {
     #[serde(default, skip_serializing_if = "Setting::is_not_set")]
     #[deserr(default)]
     pub max_values_per_facet: Setting<usize>,
+    #[serde(default, skip_serializing_if = "Setting::is_not_set")]
+    #[deserr(default)]
+    pub sort_facet_values_by: Setting<BTreeMap<String, FacetValuesSort>>,
 }
 
 #[derive(Debug, Clone, Default, Serialize, Deserialize, PartialEq, Eq, Deserr)]
@@ -398,12 +402,21 @@ pub fn apply_settings_to_builder(
         Setting::NotSet => (),
     }
 
-    match settings.faceting {
+    match &settings.faceting {
-        Setting::Set(ref value) => match value.max_values_per_facet {
+        Setting::Set(FacetingSettings { max_values_per_facet, sort_facet_values_by }) => {
-            Setting::Set(val) => builder.set_max_values_per_facet(val),
+            match max_values_per_facet {
+                Setting::Set(val) => builder.set_max_values_per_facet(*val),
                 Setting::Reset => builder.reset_max_values_per_facet(),
                 Setting::NotSet => (),
-        },
+            }
+            match sort_facet_values_by {
+                Setting::Set(val) => builder.set_sort_facet_values_by(
+                    val.iter().map(|(name, order)| (name.clone(), (*order).into())).collect(),
+                ),
+                Setting::Reset => builder.reset_sort_facet_values_by(),
+                Setting::NotSet => (),
+            }
+        }
         Setting::Reset => builder.reset_max_values_per_facet(),
         Setting::NotSet => (),
     }
@@ -476,6 +489,13 @@ pub fn settings(
         max_values_per_facet: Setting::Set(
             index.max_values_per_facet(rtxn)?.unwrap_or(DEFAULT_VALUES_PER_FACET),
         ),
+        sort_facet_values_by: Setting::Set(
+            index
+                .sort_facet_values_by(rtxn)?
+                .into_iter()
+                .map(|(name, sort)| (name, sort.into()))
+                .collect(),
+        ),
     };
 
     let pagination = PaginationSettings {

meilisearch/src/routes/indexes/search.rs

@@ -16,9 +16,9 @@ use crate::extractors::authentication::policies::*;
 use crate::extractors::authentication::GuardedData;
 use crate::extractors::sequential_extractor::SeqHandler;
 use crate::search::{
-    add_search_rules, perform_search, FacetValuesSort, MatchingStrategy, SearchQuery,
+    add_search_rules, perform_search, MatchingStrategy, SearchQuery, DEFAULT_CROP_LENGTH,
-    DEFAULT_CROP_LENGTH, DEFAULT_CROP_MARKER, DEFAULT_HIGHLIGHT_POST_TAG,
+    DEFAULT_CROP_MARKER, DEFAULT_HIGHLIGHT_POST_TAG, DEFAULT_HIGHLIGHT_PRE_TAG,
-    DEFAULT_HIGHLIGHT_PRE_TAG, DEFAULT_SEARCH_LIMIT, DEFAULT_SEARCH_OFFSET,
+    DEFAULT_SEARCH_LIMIT, DEFAULT_SEARCH_OFFSET,
 };
 
 pub fn configure(cfg: &mut web::ServiceConfig) {
@@ -64,8 +64,6 @@ pub struct SearchQueryGet {
     show_ranking_score_details: Param<bool>,
     #[deserr(default, error = DeserrQueryParamError<InvalidSearchFacets>)]
     facets: Option<CS<String>>,
-    #[deserr(default, error = DeserrQueryParamError<InvalidSearchFacets>)] // TODO
-    sort_facet_values_by: Option<FacetValuesSort>,
     #[deserr( default = DEFAULT_HIGHLIGHT_PRE_TAG(), error = DeserrQueryParamError<InvalidSearchHighlightPreTag>)]
     highlight_pre_tag: String,
     #[deserr( default = DEFAULT_HIGHLIGHT_POST_TAG(), error = DeserrQueryParamError<InvalidSearchHighlightPostTag>)]
@@ -105,7 +103,6 @@ impl From<SearchQueryGet> for SearchQuery {
             show_ranking_score: other.show_ranking_score.0,
             show_ranking_score_details: other.show_ranking_score_details.0,
             facets: other.facets.map(|o| o.into_iter().collect()),
-            sort_facet_values_by: other.sort_facet_values_by,
             highlight_pre_tag: other.highlight_pre_tag,
             highlight_post_tag: other.highlight_post_tag,
             crop_marker: other.crop_marker,

meilisearch/src/routes/indexes/settings.rs

@@ -407,6 +407,7 @@ make_setting_route!(
             json!({
                 "faceting": {
                     "max_values_per_facet": setting.as_ref().and_then(|s| s.max_values_per_facet.set()),
+                    "sort_facet_values_by": setting.as_ref().and_then(|s| s.sort_facet_values_by.clone().set()),
                 },
             }),
             Some(req),
@@ -545,6 +546,10 @@ pub async fn update_all(
                     .as_ref()
                     .set()
                     .and_then(|s| s.max_values_per_facet.as_ref().set()),
+                "sort_facet_values_by": new_settings.faceting
+                    .as_ref()
+                    .set()
+                    .and_then(|s| s.sort_facet_values_by.as_ref().set()),
             },
             "pagination": {
                 "max_total_hits": new_settings.pagination

meilisearch/src/search.rs

@@ -75,8 +75,6 @@ pub struct SearchQuery {
     pub sort: Option<Vec<String>>,
     #[deserr(default, error = DeserrJsonError<InvalidSearchFacets>)]
     pub facets: Option<Vec<String>>,
-    #[deserr(default, error = DeserrJsonError<InvalidSearchFacets>)] // TODO
-    pub sort_facet_values_by: Option<FacetValuesSort>,
     #[deserr(default, error = DeserrJsonError<InvalidSearchHighlightPreTag>, default = DEFAULT_HIGHLIGHT_PRE_TAG())]
     pub highlight_pre_tag: String,
     #[deserr(default, error = DeserrJsonError<InvalidSearchHighlightPostTag>, default = DEFAULT_HIGHLIGHT_POST_TAG())]
@@ -136,8 +134,6 @@ pub struct SearchQueryWithIndex {
     pub sort: Option<Vec<String>>,
     #[deserr(default, error = DeserrJsonError<InvalidSearchFacets>)]
     pub facets: Option<Vec<String>>,
-    #[deserr(default, error = DeserrJsonError<InvalidSearchFacets>)] // TODO
-    pub sort_facet_values_by: Option<FacetValuesSort>,
     #[deserr(default, error = DeserrJsonError<InvalidSearchHighlightPreTag>, default = DEFAULT_HIGHLIGHT_PRE_TAG())]
     pub highlight_pre_tag: String,
     #[deserr(default, error = DeserrJsonError<InvalidSearchHighlightPostTag>, default = DEFAULT_HIGHLIGHT_POST_TAG())]
@@ -170,7 +166,6 @@ impl SearchQueryWithIndex {
             filter,
             sort,
             facets,
-            sort_facet_values_by,
             highlight_pre_tag,
             highlight_post_tag,
             crop_marker,
@@ -196,7 +191,6 @@ impl SearchQueryWithIndex {
                 filter,
                 sort,
                 facets,
-                sort_facet_values_by,
                 highlight_pre_tag,
                 highlight_post_tag,
                 crop_marker,
@@ -581,12 +575,29 @@ pub fn perform_search(
                 .unwrap_or(DEFAULT_VALUES_PER_FACET);
             facet_distribution.max_values_per_facet(max_values_by_facet);
 
+            let sort_facet_values_by =
+                index.sort_facet_values_by(&rtxn).map_err(milli::Error::from)?;
+            let default_sort_facet_values_by =
+                sort_facet_values_by.get("*").copied().unwrap_or_default();
+
             if fields.iter().all(|f| f != "*") {
+                let fields: Vec<_> = fields
+                    .into_iter()
+                    .map(|n| {
+                        (
+                            n,
+                            sort_facet_values_by
+                                .get(n)
+                                .copied()
+                                .unwrap_or(default_sort_facet_values_by),
+                        )
+                    })
+                    .collect();
                 facet_distribution.facets(fields);
             }
             let distribution = facet_distribution
                 .candidates(candidates)
-                .order_by(query.sort_facet_values_by.map_or_else(Default::default, Into::into))
+                .default_order_by(default_sort_facet_values_by)
                 .execute()?;
             let stats = facet_distribution.compute_stats()?;
             (Some(distribution), Some(stats))

milli/src/index.rs

@@ -26,7 +26,8 @@ use crate::readable_slices::ReadableSlices;
 use crate::{
     default_criteria, CboRoaringBitmapCodec, Criterion, DocumentId, ExternalDocumentsIds,
     FacetDistribution, FieldDistribution, FieldId, FieldIdWordCountCodec, GeoPoint, ObkvCodec,
-    Result, RoaringBitmapCodec, RoaringBitmapLenCodec, Search, U8StrStrCodec, BEU16, BEU32,
+    OrderBy, Result, RoaringBitmapCodec, RoaringBitmapLenCodec, Search, U8StrStrCodec, BEU16,
+    BEU32,
 };
 
 /// The HNSW data-structure that we serialize, fill and search in.
@@ -71,6 +72,7 @@ pub mod main_key {
     pub const EXACT_WORDS: &str = "exact-words";
     pub const EXACT_ATTRIBUTES: &str = "exact-attributes";
     pub const MAX_VALUES_PER_FACET: &str = "max-values-per-facet";
+    pub const SORT_FACET_VALUES_BY: &str = "sort-facet-values-by";
     pub const PAGINATION_MAX_TOTAL_HITS: &str = "pagination-max-total-hits";
 }
 
@@ -1298,6 +1300,31 @@ impl Index {
         self.main.delete::<_, Str>(txn, main_key::MAX_VALUES_PER_FACET)
     }
 
+    pub fn sort_facet_values_by(&self, txn: &RoTxn) -> heed::Result<HashMap<String, OrderBy>> {
+        let mut orders = self
+            .main
+            .get::<_, Str, SerdeJson<HashMap<String, OrderBy>>>(
+                txn,
+                main_key::SORT_FACET_VALUES_BY,
+            )?
+            .unwrap_or_default();
+        // Insert the default ordering if it is not already overwritten by the user.
+        orders.entry("*".to_string()).or_insert(OrderBy::Lexicographic);
+        Ok(orders)
+    }
+
+    pub(crate) fn put_sort_facet_values_by(
+        &self,
+        txn: &mut RwTxn,
+        val: &HashMap<String, OrderBy>,
+    ) -> heed::Result<()> {
+        self.main.put::<_, Str, SerdeJson<_>>(txn, main_key::SORT_FACET_VALUES_BY, &val)
+    }
+
+    pub(crate) fn delete_sort_facet_values_by(&self, txn: &mut RwTxn) -> heed::Result<bool> {
+        self.main.delete::<_, Str>(txn, main_key::SORT_FACET_VALUES_BY)
+    }
+
     pub fn pagination_max_total_hits(&self, txn: &RoTxn) -> heed::Result<Option<usize>> {
         self.main.get::<_, Str, OwnedType<usize>>(txn, main_key::PAGINATION_MAX_TOTAL_HITS)
     }

milli/src/search/facet/facet_distribution.rs

@@ -1,4 +1,4 @@
-use std::collections::{BTreeMap, HashSet};
+use std::collections::{BTreeMap, HashMap, HashSet};
 use std::ops::ControlFlow;
 use std::{fmt, mem};
 
@@ -6,6 +6,7 @@ use heed::types::ByteSlice;
 use heed::BytesDecode;
 use indexmap::IndexMap;
 use roaring::RoaringBitmap;
+use serde::{Deserialize, Serialize};
 
 use crate::error::UserError;
 use crate::facet::FacetType;
@@ -27,7 +28,7 @@ pub const DEFAULT_VALUES_PER_FACET: usize = 100;
 const CANDIDATES_THRESHOLD: u64 = 3000;
 
 /// How should we fetch the facets?
-#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
 pub enum OrderBy {
     /// By lexicographic order...
     #[default]
@@ -37,10 +38,10 @@ pub enum OrderBy {
 }
 
 pub struct FacetDistribution<'a> {
-    facets: Option<HashSet<String>>,
+    facets: Option<HashMap<String, OrderBy>>,
     candidates: Option<RoaringBitmap>,
     max_values_per_facet: usize,
-    order_by: OrderBy,
+    default_order_by: OrderBy,
     rtxn: &'a heed::RoTxn<'a>,
     index: &'a Index,
 }
@@ -51,14 +52,22 @@ impl<'a> FacetDistribution<'a> {
             facets: None,
             candidates: None,
             max_values_per_facet: DEFAULT_VALUES_PER_FACET,
-            order_by: OrderBy::default(),
+            default_order_by: OrderBy::default(),
             rtxn,
             index,
         }
     }
 
-    pub fn facets<I: IntoIterator<Item = A>, A: AsRef<str>>(&mut self, names: I) -> &mut Self {
+    pub fn facets<I: IntoIterator<Item = (A, OrderBy)>, A: AsRef<str>>(
-        self.facets = Some(names.into_iter().map(|s| s.as_ref().to_string()).collect());
+        &mut self,
+        names_ordered_by: I,
+    ) -> &mut Self {
+        self.facets = Some(
+            names_ordered_by
+                .into_iter()
+                .map(|(name, order_by)| (name.as_ref().to_string(), order_by))
+                .collect(),
+        );
         self
     }
 
@@ -67,8 +76,8 @@ impl<'a> FacetDistribution<'a> {
         self
     }
 
-    pub fn order_by(&mut self, order_by: OrderBy) -> &mut Self {
+    pub fn default_order_by(&mut self, order_by: OrderBy) -> &mut Self {
-        self.order_by = order_by;
+        self.default_order_by = order_by;
         self
     }
 
@@ -220,11 +229,15 @@ impl<'a> FacetDistribution<'a> {
         )
     }
 
-    fn facet_values(&self, field_id: FieldId) -> heed::Result<IndexMap<String, u64>> {
+    fn facet_values(
+        &self,
+        field_id: FieldId,
+        order_by: OrderBy,
+    ) -> heed::Result<IndexMap<String, u64>> {
         use FacetType::{Number, String};
 
         let mut distribution = IndexMap::new();
-        match (self.order_by, &self.candidates) {
+        match (order_by, &self.candidates) {
             (OrderBy::Lexicographic, Some(cnd)) if cnd.len() <= CANDIDATES_THRESHOLD => {
                 // Classic search, candidates were specified, we must return facet values only related
                 // to those candidates. We also enter here for facet strings for performance reasons.
@@ -245,13 +258,13 @@ impl<'a> FacetDistribution<'a> {
                 self.facet_numbers_distribution_from_facet_levels(
                     field_id,
                     candidates,
-                    self.order_by,
+                    order_by,
                     &mut distribution,
                 )?;
                 self.facet_strings_distribution_from_facet_levels(
                     field_id,
                     candidates,
-                    self.order_by,
+                    order_by,
                     &mut distribution,
                 )?;
             }
@@ -273,6 +286,7 @@ impl<'a> FacetDistribution<'a> {
             Some(facets) => {
                 let invalid_fields: HashSet<_> = facets
                     .iter()
+                    .map(|(name, _)| name)
                     .filter(|facet| !crate::is_faceted(facet, &filterable_fields))
                     .collect();
                 if !invalid_fields.is_empty() {
@@ -282,7 +296,7 @@ impl<'a> FacetDistribution<'a> {
                     }
                     .into());
                 } else {
-                    facets.clone()
+                    facets.into_iter().map(|(name, _)| name).cloned().collect()
                 }
             }
             None => filterable_fields,
@@ -327,6 +341,7 @@ impl<'a> FacetDistribution<'a> {
             Some(ref facets) => {
                 let invalid_fields: HashSet<_> = facets
                     .iter()
+                    .map(|(name, _)| name)
                     .filter(|facet| !crate::is_faceted(facet, &filterable_fields))
                     .collect();
                 if !invalid_fields.is_empty() {
@@ -336,7 +351,7 @@ impl<'a> FacetDistribution<'a> {
                     }
                     .into());
                 } else {
-                    facets.clone()
+                    facets.into_iter().map(|(name, _)| name).cloned().collect()
                 }
             }
             None => filterable_fields,
@@ -345,7 +360,13 @@ impl<'a> FacetDistribution<'a> {
         let mut distribution = BTreeMap::new();
         for (fid, name) in fields_ids_map.iter() {
             if crate::is_faceted(name, &fields) {
-                let values = self.facet_values(fid)?;
+                let order_by = self
+                    .facets
+                    .as_ref()
+                    .map(|facets| facets.get(name).copied())
+                    .flatten()
+                    .unwrap_or(self.default_order_by);
+                let values = self.facet_values(fid, order_by)?;
                 distribution.insert(name.to_string(), values);
             }
         }
@@ -360,7 +381,7 @@ impl fmt::Debug for FacetDistribution<'_> {
             facets,
             candidates,
             max_values_per_facet,
-            order_by,
+            default_order_by,
             rtxn: _,
             index: _,
         } = self;
@@ -369,7 +390,7 @@ impl fmt::Debug for FacetDistribution<'_> {
             .field("facets", facets)
             .field("candidates", candidates)
             .field("max_values_per_facet", max_values_per_facet)
-            .field("order_by", order_by)
+            .field("default_order_by", default_order_by)
             .finish()
     }
 }
@@ -381,7 +402,7 @@ mod tests {
 
     use crate::documents::documents_batch_reader_from_objects;
     use crate::index::tests::TempIndex;
-    use crate::{milli_snap, FacetDistribution};
+    use crate::{milli_snap, FacetDistribution, OrderBy};
 
     #[test]
     fn few_candidates_few_facet_values() {
@@ -406,14 +427,14 @@ mod tests {
         let txn = index.read_txn().unwrap();
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .execute()
             .unwrap();
 
         milli_snap!(format!("{map:?}"), @r###"{"colour": {"Blue": 2, "RED": 1}}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates([0, 1, 2].iter().copied().collect())
             .execute()
             .unwrap();
@@ -421,7 +442,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), @r###"{"colour": {"Blue": 2, "RED": 1}}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates([1, 2].iter().copied().collect())
             .execute()
             .unwrap();
@@ -432,7 +453,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), @r###"{"colour": {"  blue": 1, "RED": 1}}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates([2].iter().copied().collect())
             .execute()
             .unwrap();
@@ -440,7 +461,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), @r###"{"colour": {"RED": 1}}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates([0, 1, 2].iter().copied().collect())
             .max_values_per_facet(1)
             .execute()
@@ -478,14 +499,14 @@ mod tests {
         let txn = index.read_txn().unwrap();
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .execute()
             .unwrap();
 
         milli_snap!(format!("{map:?}"), @r###"{"colour": {"Blue": 4000, "Red": 6000}}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .max_values_per_facet(1)
             .execute()
             .unwrap();
@@ -493,7 +514,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), @r###"{"colour": {"Blue": 4000}}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((0..10_000).collect())
             .execute()
             .unwrap();
@@ -501,7 +522,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), @r###"{"colour": {"Blue": 4000, "Red": 6000}}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((0..5_000).collect())
             .execute()
             .unwrap();
@@ -509,7 +530,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), @r###"{"colour": {"Blue": 2000, "Red": 3000}}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((0..5_000).collect())
             .execute()
             .unwrap();
@@ -517,7 +538,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), @r###"{"colour": {"Blue": 2000, "Red": 3000}}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((0..5_000).collect())
             .max_values_per_facet(1)
             .execute()
@@ -555,14 +576,14 @@ mod tests {
         let txn = index.read_txn().unwrap();
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .execute()
             .unwrap();
 
         milli_snap!(format!("{map:?}"), "no_candidates", @"ac9229ed5964d893af96a7076e2f8af5");
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .max_values_per_facet(2)
             .execute()
             .unwrap();
@@ -570,7 +591,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), "no_candidates_with_max_2", @r###"{"colour": {"0": 10, "1": 10}}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((0..10_000).collect())
             .execute()
             .unwrap();
@@ -578,7 +599,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), "candidates_0_10_000", @"ac9229ed5964d893af96a7076e2f8af5");
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((0..5_000).collect())
             .execute()
             .unwrap();
@@ -615,14 +636,14 @@ mod tests {
         let txn = index.read_txn().unwrap();
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .compute_stats()
             .unwrap();
 
         milli_snap!(format!("{map:?}"), "no_candidates", @"{}");
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((0..1000).collect())
             .compute_stats()
             .unwrap();
@@ -630,7 +651,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), "candidates_0_1000", @r###"{"colour": (0.0, 999.0)}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((217..777).collect())
             .compute_stats()
             .unwrap();
@@ -667,14 +688,14 @@ mod tests {
         let txn = index.read_txn().unwrap();
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .compute_stats()
             .unwrap();
 
         milli_snap!(format!("{map:?}"), "no_candidates", @"{}");
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((0..1000).collect())
             .compute_stats()
             .unwrap();
@@ -682,7 +703,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), "candidates_0_1000", @r###"{"colour": (0.0, 1999.0)}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((217..777).collect())
             .compute_stats()
             .unwrap();
@@ -719,14 +740,14 @@ mod tests {
         let txn = index.read_txn().unwrap();
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .compute_stats()
             .unwrap();
 
         milli_snap!(format!("{map:?}"), "no_candidates", @"{}");
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((0..1000).collect())
             .compute_stats()
             .unwrap();
@@ -734,7 +755,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), "candidates_0_1000", @r###"{"colour": (0.0, 999.0)}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((217..777).collect())
             .compute_stats()
             .unwrap();
@@ -775,14 +796,14 @@ mod tests {
         let txn = index.read_txn().unwrap();
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .compute_stats()
             .unwrap();
 
         milli_snap!(format!("{map:?}"), "no_candidates", @"{}");
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((0..1000).collect())
             .compute_stats()
             .unwrap();
@@ -790,7 +811,7 @@ mod tests {
         milli_snap!(format!("{map:?}"), "candidates_0_1000", @r###"{"colour": (0.0, 1998.0)}"###);
 
         let map = FacetDistribution::new(&txn, &index)
-            .facets(std::iter::once("colour"))
+            .facets(std::iter::once(("colour", OrderBy::default())))
             .candidates((217..777).collect())
             .compute_stats()
             .unwrap();

milli/src/update/settings.rs

@@ -14,7 +14,7 @@ use crate::error::UserError;
 use crate::index::{DEFAULT_MIN_WORD_LEN_ONE_TYPO, DEFAULT_MIN_WORD_LEN_TWO_TYPOS};
 use crate::update::index_documents::IndexDocumentsMethod;
 use crate::update::{IndexDocuments, UpdateIndexingStep};
-use crate::{FieldsIdsMap, Index, Result};
+use crate::{FieldsIdsMap, Index, OrderBy, Result};
 
 #[derive(Debug, Clone, PartialEq, Eq, Copy)]
 pub enum Setting<T> {
@@ -122,6 +122,7 @@ pub struct Settings<'a, 't, 'u, 'i> {
     /// Attributes on which typo tolerance is disabled.
     exact_attributes: Setting<HashSet<String>>,
     max_values_per_facet: Setting<usize>,
+    sort_facet_values_by: Setting<HashMap<String, OrderBy>>,
     pagination_max_total_hits: Setting<usize>,
 }
 
@@ -149,6 +150,7 @@ impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
             min_word_len_one_typo: Setting::NotSet,
             exact_attributes: Setting::NotSet,
             max_values_per_facet: Setting::NotSet,
+            sort_facet_values_by: Setting::NotSet,
             pagination_max_total_hits: Setting::NotSet,
             indexer_config,
         }
@@ -275,6 +277,14 @@ impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
         self.max_values_per_facet = Setting::Reset;
     }
 
+    pub fn set_sort_facet_values_by(&mut self, value: HashMap<String, OrderBy>) {
+        self.sort_facet_values_by = Setting::Set(value);
+    }
+
+    pub fn reset_sort_facet_values_by(&mut self) {
+        self.sort_facet_values_by = Setting::Reset;
+    }
+
     pub fn set_pagination_max_total_hits(&mut self, value: usize) {
         self.pagination_max_total_hits = Setting::Set(value);
     }
@@ -680,6 +690,20 @@ impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
         Ok(())
     }
 
+    fn update_sort_facet_values_by(&mut self) -> Result<()> {
+        match self.sort_facet_values_by.as_ref() {
+            Setting::Set(value) => {
+                self.index.put_sort_facet_values_by(self.wtxn, value)?;
+            }
+            Setting::Reset => {
+                self.index.delete_sort_facet_values_by(self.wtxn)?;
+            }
+            Setting::NotSet => (),
+        }
+
+        Ok(())
+    }
+
     fn update_pagination_max_total_hits(&mut self) -> Result<()> {
         match self.pagination_max_total_hits {
             Setting::Set(max) => {
@@ -714,6 +738,7 @@ impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
         self.update_min_typo_word_len()?;
         self.update_exact_words()?;
         self.update_max_values_per_facet()?;
+        self.update_sort_facet_values_by()?;
         self.update_pagination_max_total_hits()?;
 
         // If there is new faceted fields we indicate that we must reindex as we must
@@ -1515,6 +1540,7 @@ mod tests {
                     exact_words,
                     exact_attributes,
                     max_values_per_facet,
+                    sort_facet_values_by,
                     pagination_max_total_hits,
                 } = settings;
                 assert!(matches!(searchable_fields, Setting::NotSet));
@@ -1532,6 +1558,7 @@ mod tests {
                 assert!(matches!(exact_words, Setting::NotSet));
                 assert!(matches!(exact_attributes, Setting::NotSet));
                 assert!(matches!(max_values_per_facet, Setting::NotSet));
+                assert!(matches!(sort_facet_values_by, Setting::NotSet));
                 assert!(matches!(pagination_max_total_hits, Setting::NotSet));
             })
             .unwrap();

milli/tests/search/facet_distribution.rs

@@ -5,7 +5,7 @@ use heed::EnvOpenOptions;
 use maplit::hashset;
 use milli::documents::{DocumentsBatchBuilder, DocumentsBatchReader};
 use milli::update::{IndexDocuments, IndexDocumentsConfig, IndexerConfig, Settings};
-use milli::{FacetDistribution, Index, Object};
+use milli::{FacetDistribution, Index, Object, OrderBy};
 use serde_json::Deserializer;
 
 #[test]
@@ -63,12 +63,12 @@ fn test_facet_distribution_with_no_facet_values() {
 
     let txn = index.read_txn().unwrap();
     let mut distrib = FacetDistribution::new(&txn, &index);
-    distrib.facets(vec!["genres"]);
+    distrib.facets(vec![("genres", OrderBy::default())]);
     let result = distrib.execute().unwrap();
     assert_eq!(result["genres"].len(), 0);
 
     let mut distrib = FacetDistribution::new(&txn, &index);
-    distrib.facets(vec!["tags"]);
+    distrib.facets(vec![("tags", OrderBy::default())]);
     let result = distrib.execute().unwrap();
     assert_eq!(result["tags"].len(), 2);
 }