Rename the hits and query output into facetHits and facetQuery respectively

3792: fix the type of the document deletion by filter tasks r=dureuill a=irevoire

# Pull Request

## Related issue
Fixes https://github.com/meilisearch/meilisearch/issues/3791

## What does this PR do?
- Hide the deleteDocumentByFilter internal type from the users.


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

Cargo.lock

@@ -2730,7 +2730,6 @@ dependencies = [
  "geoutils",
  "grenad",
  "heed",
- "indexmap",
  "insta",
  "itertools",
  "json-depth-checker",

index-scheduler/src/utils.rs

@@ -466,7 +466,7 @@ impl IndexScheduler {
                         }
                     }
                     Details::DocumentDeletionByFilter { deleted_documents, original_filter: _ } => {
-                        assert_eq!(kind.as_kind(), Kind::DocumentDeletionByFilter);
+                        assert_eq!(kind.as_kind(), Kind::DocumentDeletion);
                         let (index_uid, _) = if let KindWithContent::DocumentDeletionByFilter {
                             ref index_uid,
                             ref filter_expr,

meilisearch-types/src/deserr/mod.rs

@@ -151,6 +151,10 @@ make_missing_field_convenience_builder!(MissingApiKeyExpiresAt, missing_api_key_
 make_missing_field_convenience_builder!(MissingApiKeyIndexes, missing_api_key_indexes);
 make_missing_field_convenience_builder!(MissingSwapIndexes, missing_swap_indexes);
 make_missing_field_convenience_builder!(MissingDocumentFilter, missing_document_filter);
+make_missing_field_convenience_builder!(
+    MissingFacetSearchFacetName,
+    missing_facet_search_facet_name
+);
 
 // Integrate a sub-error into a [`DeserrError`] by taking its error message but using
 // the default error code (C) from `Self`

meilisearch-types/src/error.rs

@@ -230,6 +230,7 @@ InvalidSearchAttributesToRetrieve     , InvalidRequest       , BAD_REQUEST ;
 InvalidSearchCropLength               , InvalidRequest       , BAD_REQUEST ;
 InvalidSearchCropMarker               , InvalidRequest       , BAD_REQUEST ;
 InvalidSearchFacets                   , InvalidRequest       , BAD_REQUEST ;
+InvalidFacetSearchFacetName           , InvalidRequest       , BAD_REQUEST ;
 InvalidSearchFilter                   , InvalidRequest       , BAD_REQUEST ;
 InvalidSearchHighlightPostTag         , InvalidRequest       , BAD_REQUEST ;
 InvalidSearchHighlightPreTag          , InvalidRequest       , BAD_REQUEST ;
@@ -239,8 +240,11 @@ InvalidSearchMatchingStrategy         , InvalidRequest       , BAD_REQUEST ;
 InvalidSearchOffset                   , InvalidRequest       , BAD_REQUEST ;
 InvalidSearchPage                     , InvalidRequest       , BAD_REQUEST ;
 InvalidSearchQ                        , InvalidRequest       , BAD_REQUEST ;
+InvalidFacetSearchQuery               , InvalidRequest       , BAD_REQUEST ;
+InvalidFacetSearchName                , InvalidRequest       , BAD_REQUEST ;
 InvalidSearchShowMatchesPosition      , InvalidRequest       , BAD_REQUEST ;
 InvalidSearchSort                     , InvalidRequest       , BAD_REQUEST ;
+InvalidSearchFacet                    , InvalidRequest       , BAD_REQUEST ;
 InvalidSettingsDisplayedAttributes    , InvalidRequest       , BAD_REQUEST ;
 InvalidSettingsDistinctAttribute      , InvalidRequest       , BAD_REQUEST ;
 InvalidSettingsFaceting               , InvalidRequest       , BAD_REQUEST ;
@@ -277,6 +281,7 @@ MissingApiKeyIndexes                  , InvalidRequest       , BAD_REQUEST ;
 MissingAuthorizationHeader            , Auth                 , UNAUTHORIZED ;
 MissingContentType                    , InvalidRequest       , UNSUPPORTED_MEDIA_TYPE ;
 MissingDocumentId                     , InvalidRequest       , BAD_REQUEST ;
+MissingFacetSearchFacetName           , InvalidRequest       , BAD_REQUEST ;
 MissingIndexUid                       , InvalidRequest       , BAD_REQUEST ;
 MissingMasterKey                      , Auth                 , UNAUTHORIZED ;
 MissingPayload                        , InvalidRequest       , BAD_REQUEST ;
@@ -330,6 +335,9 @@ impl ErrorCode for milli::Error {
                     UserError::SortRankingRuleMissing => Code::InvalidSearchSort,
                     UserError::InvalidFacetsDistribution { .. } => Code::InvalidSearchFacets,
                     UserError::InvalidSortableAttribute { .. } => Code::InvalidSearchSort,
+                    UserError::InvalidFacetSearchFacetName { .. } => {
+                        Code::InvalidFacetSearchFacetName
+                    }
                     UserError::CriterionError(_) => Code::InvalidSettingsRankingRules,
                     UserError::InvalidGeoField { .. } => Code::InvalidDocumentGeoField,
                     UserError::SortError(_) => Code::InvalidSearchSort,

meilisearch-types/src/tasks.rs

@@ -395,7 +395,6 @@ impl std::error::Error for ParseTaskStatusError {}
 pub enum Kind {
     DocumentAdditionOrUpdate,
     DocumentDeletion,
-    DocumentDeletionByFilter,
     SettingsUpdate,
     IndexCreation,
     IndexDeletion,
@@ -412,7 +411,6 @@ impl Kind {
         match self {
             Kind::DocumentAdditionOrUpdate
             | Kind::DocumentDeletion
-            | Kind::DocumentDeletionByFilter
             | Kind::SettingsUpdate
             | Kind::IndexCreation
             | Kind::IndexDeletion
@@ -430,7 +428,6 @@ impl Display for Kind {
         match self {
             Kind::DocumentAdditionOrUpdate => write!(f, "documentAdditionOrUpdate"),
             Kind::DocumentDeletion => write!(f, "documentDeletion"),
-            Kind::DocumentDeletionByFilter => write!(f, "documentDeletionByFilter"),
             Kind::SettingsUpdate => write!(f, "settingsUpdate"),
             Kind::IndexCreation => write!(f, "indexCreation"),
             Kind::IndexDeletion => write!(f, "indexDeletion"),

meilisearch/Cargo.toml

@@ -14,27 +14,14 @@ default-run = "meilisearch"
 
 [dependencies]
 actix-cors = "0.6.4"
-actix-http = { version = "3.3.1", default-features = false, features = [
-    "compress-brotli",
-    "compress-gzip",
-    "rustls",
-] }
-actix-web = { version = "4.3.1", default-features = false, features = [
-    "macros",
-    "compress-brotli",
-    "compress-gzip",
-    "cookies",
-    "rustls",
-] }
+actix-http = { version = "3.3.1", default-features = false, features = ["compress-brotli", "compress-gzip", "rustls"] }
+actix-web = { version = "4.3.1", default-features = false, features = ["macros", "compress-brotli", "compress-gzip", "cookies", "rustls"] }
 actix-web-static-files = { git = "https://github.com/kilork/actix-web-static-files.git", rev = "2d3b6160", optional = true }
 anyhow = { version = "1.0.70", features = ["backtrace"] }
 async-stream = "0.3.5"
 async-trait = "0.1.68"
 bstr = "1.4.0"
-byte-unit = { version = "4.0.19", default-features = false, features = [
-    "std",
-    "serde",
-] }
+byte-unit = { version = "4.0.19", default-features = false, features = ["std", "serde"] }
 bytes = "1.4.0"
 clap = { version = "4.2.1", features = ["derive", "env"] }
 crossbeam-channel = "0.5.8"
@@ -69,10 +56,7 @@ prometheus = { version = "0.13.3", features = ["process"] }
 rand = "0.8.5"
 rayon = "1.7.0"
 regex = "1.7.3"
-reqwest = { version = "0.11.16", features = [
-    "rustls-tls",
-    "json",
-], default-features = false }
+reqwest = { version = "0.11.16", features = ["rustls-tls", "json"], default-features = false }
 rustls = "0.20.8"
 rustls-pemfile = "1.0.2"
 segment = { version = "0.2.2", optional = true }
@@ -86,12 +70,7 @@ sysinfo = "0.28.4"
 tar = "0.4.38"
 tempfile = "3.5.0"
 thiserror = "1.0.40"
-time = { version = "0.3.20", features = [
-    "serde-well-known",
-    "formatting",
-    "parsing",
-    "macros",
-] }
+time = { version = "0.3.20", features = ["serde-well-known", "formatting", "parsing", "macros"] }
 tokio = { version = "1.27.0", features = ["full"] }
 tokio-stream = "0.1.12"
 toml = "0.7.3"
@@ -110,7 +89,7 @@ brotli = "3.3.4"
 insta = "1.29.0"
 manifest-dir-macros = "0.1.16"
 maplit = "1.0.2"
-meili-snap = { path = "../meili-snap" }
+meili-snap = {path = "../meili-snap"}
 temp-env = "0.3.3"
 urlencoding = "2.1.2"
 yaup = "0.2.1"
@@ -119,10 +98,7 @@ yaup = "0.2.1"
 anyhow = { version = "1.0.70", optional = true }
 cargo_toml = { version = "0.15.2", optional = true }
 hex = { version = "0.4.3", optional = true }
-reqwest = { version = "0.11.16", features = [
-    "blocking",
-    "rustls-tls",
-], default-features = false, optional = true }
+reqwest = { version = "0.11.16", features = ["blocking", "rustls-tls"], default-features = false, optional = true }
 sha-1 = { version = "0.10.1", optional = true }
 static-files = { version = "0.2.3", optional = true }
 tempfile = { version = "3.5.0", optional = true }
@@ -132,17 +108,7 @@ zip = { version = "0.6.4", optional = true }
 [features]
 default = ["analytics", "meilisearch-types/all-tokenizations", "mini-dashboard"]
 analytics = ["segment"]
-mini-dashboard = [
-    "actix-web-static-files",
-    "static-files",
-    "anyhow",
-    "cargo_toml",
-    "hex",
-    "reqwest",
-    "sha-1",
-    "tempfile",
-    "zip",
-]
+mini-dashboard = ["actix-web-static-files", "static-files", "anyhow", "cargo_toml", "hex", "reqwest", "sha-1", "tempfile", "zip"]
 chinese = ["meilisearch-types/chinese"]
 hebrew = ["meilisearch-types/hebrew"]
 japanese = ["meilisearch-types/japanese"]

meilisearch/src/analytics/mock_analytics.rs

@@ -38,6 +38,18 @@ impl MultiSearchAggregator {
     pub fn succeed(&mut self) {}
 }
 
+#[derive(Default)]
+pub struct FacetSearchAggregator;
+
+#[allow(dead_code)]
+impl FacetSearchAggregator {
+    pub fn from_query(_: &dyn Any, _: &dyn Any) -> Self {
+        Self::default()
+    }
+
+    pub fn succeed(&mut self, _: &dyn Any) {}
+}
+
 impl MockAnalytics {
     #[allow(clippy::new_ret_no_self)]
     pub fn new(opt: &Opt) -> Arc<dyn Analytics> {
@@ -56,6 +68,7 @@ impl Analytics for MockAnalytics {
     fn get_search(&self, _aggregate: super::SearchAggregator) {}
     fn post_search(&self, _aggregate: super::SearchAggregator) {}
     fn post_multi_search(&self, _aggregate: super::MultiSearchAggregator) {}
+    fn post_facet_search(&self, _aggregate: super::FacetSearchAggregator) {}
     fn add_documents(
         &self,
         _documents_query: &UpdateDocumentsQuery,

meilisearch/src/analytics/mod.rs

@@ -25,6 +25,8 @@ pub type SegmentAnalytics = mock_analytics::MockAnalytics;
 pub type SearchAggregator = mock_analytics::SearchAggregator;
 #[cfg(any(debug_assertions, not(feature = "analytics")))]
 pub type MultiSearchAggregator = mock_analytics::MultiSearchAggregator;
+#[cfg(any(debug_assertions, not(feature = "analytics")))]
+pub type FacetSearchAggregator = mock_analytics::FacetSearchAggregator;
 
 // if we are in release mode and the feature analytics was enabled
 // we use the real analytics
@@ -34,6 +36,8 @@ pub type SegmentAnalytics = segment_analytics::SegmentAnalytics;
 pub type SearchAggregator = segment_analytics::SearchAggregator;
 #[cfg(all(not(debug_assertions), feature = "analytics"))]
 pub type MultiSearchAggregator = segment_analytics::MultiSearchAggregator;
+#[cfg(all(not(debug_assertions), feature = "analytics"))]
+pub type FacetSearchAggregator = segment_analytics::FacetSearchAggregator;
 
 /// The Meilisearch config dir:
 /// `~/.config/Meilisearch` on *NIX or *BSD.
@@ -88,6 +92,9 @@ pub trait Analytics: Sync + Send {
     /// This method should be called to aggregate a post array of searches
     fn post_multi_search(&self, aggregate: MultiSearchAggregator);
 
+    /// This method should be called to aggregate post facet values searches
+    fn post_facet_search(&self, aggregate: FacetSearchAggregator);
+
     // this method should be called to aggregate a add documents request
     fn add_documents(
         &self,

meilisearch/src/analytics/segment_analytics.rs

@@ -1,5 +1,6 @@
 use std::collections::{BinaryHeap, HashMap, HashSet};
 use std::fs;
+use std::mem::take;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 use std::time::{Duration, Instant};
@@ -29,11 +30,13 @@ use super::{
 use crate::analytics::Analytics;
 use crate::option::{default_http_addr, IndexerOpts, MaxMemory, MaxThreads, ScheduleSnapshot};
 use crate::routes::indexes::documents::UpdateDocumentsQuery;
+use crate::routes::indexes::facet_search::FacetSearchQuery;
 use crate::routes::tasks::TasksFilterQuery;
 use crate::routes::{create_all_stats, Stats};
 use crate::search::{
-    SearchQuery, SearchQueryWithIndex, SearchResult, DEFAULT_CROP_LENGTH, DEFAULT_CROP_MARKER,
-    DEFAULT_HIGHLIGHT_POST_TAG, DEFAULT_HIGHLIGHT_PRE_TAG, DEFAULT_SEARCH_LIMIT,
+    FacetSearchResult, MatchingStrategy, SearchQuery, SearchQueryWithIndex, SearchResult,
+    DEFAULT_CROP_LENGTH, DEFAULT_CROP_MARKER, DEFAULT_HIGHLIGHT_POST_TAG,
+    DEFAULT_HIGHLIGHT_PRE_TAG, DEFAULT_SEARCH_LIMIT, DEFAULT_SEARCH_OFFSET,
 };
 use crate::Opt;
 
@@ -71,6 +74,7 @@ pub enum AnalyticsMsg {
     AggregateGetSearch(SearchAggregator),
     AggregatePostSearch(SearchAggregator),
     AggregatePostMultiSearch(MultiSearchAggregator),
+    AggregatePostFacetSearch(FacetSearchAggregator),
     AggregateAddDocuments(DocumentsAggregator),
     AggregateDeleteDocuments(DocumentsDeletionAggregator),
     AggregateUpdateDocuments(DocumentsAggregator),
@@ -139,6 +143,7 @@ impl SegmentAnalytics {
             batcher,
             post_search_aggregator: SearchAggregator::default(),
             post_multi_search_aggregator: MultiSearchAggregator::default(),
+            post_facet_search_aggregator: FacetSearchAggregator::default(),
             get_search_aggregator: SearchAggregator::default(),
             add_documents_aggregator: DocumentsAggregator::default(),
             delete_documents_aggregator: DocumentsDeletionAggregator::default(),
@@ -182,6 +187,10 @@ impl super::Analytics for SegmentAnalytics {
         let _ = self.sender.try_send(AnalyticsMsg::AggregatePostSearch(aggregate));
     }
 
+    fn post_facet_search(&self, aggregate: FacetSearchAggregator) {
+        let _ = self.sender.try_send(AnalyticsMsg::AggregatePostFacetSearch(aggregate));
+    }
+
     fn post_multi_search(&self, aggregate: MultiSearchAggregator) {
         let _ = self.sender.try_send(AnalyticsMsg::AggregatePostMultiSearch(aggregate));
     }
@@ -354,6 +363,7 @@ pub struct Segment {
     get_search_aggregator: SearchAggregator,
     post_search_aggregator: SearchAggregator,
     post_multi_search_aggregator: MultiSearchAggregator,
+    post_facet_search_aggregator: FacetSearchAggregator,
     add_documents_aggregator: DocumentsAggregator,
     delete_documents_aggregator: DocumentsDeletionAggregator,
     update_documents_aggregator: DocumentsAggregator,
@@ -418,6 +428,7 @@ impl Segment {
                         Some(AnalyticsMsg::AggregateGetSearch(agreg)) => self.get_search_aggregator.aggregate(agreg),
                         Some(AnalyticsMsg::AggregatePostSearch(agreg)) => self.post_search_aggregator.aggregate(agreg),
                         Some(AnalyticsMsg::AggregatePostMultiSearch(agreg)) => self.post_multi_search_aggregator.aggregate(agreg),
+                        Some(AnalyticsMsg::AggregatePostFacetSearch(agreg)) => self.post_facet_search_aggregator.aggregate(agreg),
                         Some(AnalyticsMsg::AggregateAddDocuments(agreg)) => self.add_documents_aggregator.aggregate(agreg),
                         Some(AnalyticsMsg::AggregateDeleteDocuments(agreg)) => self.delete_documents_aggregator.aggregate(agreg),
                         Some(AnalyticsMsg::AggregateUpdateDocuments(agreg)) => self.update_documents_aggregator.aggregate(agreg),
@@ -461,55 +472,72 @@ impl Segment {
                 })
                 .await;
         }
-        let get_search = std::mem::take(&mut self.get_search_aggregator)
-            .into_event(&self.user, "Documents Searched GET");
-        let post_search = std::mem::take(&mut self.post_search_aggregator)
-            .into_event(&self.user, "Documents Searched POST");
-        let post_multi_search = std::mem::take(&mut self.post_multi_search_aggregator)
-            .into_event(&self.user, "Documents Searched by Multi-Search POST");
-        let add_documents = std::mem::take(&mut self.add_documents_aggregator)
-            .into_event(&self.user, "Documents Added");
-        let delete_documents = std::mem::take(&mut self.delete_documents_aggregator)
-            .into_event(&self.user, "Documents Deleted");
-        let update_documents = std::mem::take(&mut self.update_documents_aggregator)
-            .into_event(&self.user, "Documents Updated");
-        let get_fetch_documents = std::mem::take(&mut self.get_fetch_documents_aggregator)
-            .into_event(&self.user, "Documents Fetched GET");
-        let post_fetch_documents = std::mem::take(&mut self.post_fetch_documents_aggregator)
-            .into_event(&self.user, "Documents Fetched POST");
-        let get_tasks =
-            std::mem::take(&mut self.get_tasks_aggregator).into_event(&self.user, "Tasks Seen");
-        let health =
-            std::mem::take(&mut self.health_aggregator).into_event(&self.user, "Health Seen");
 
-        if let Some(get_search) = get_search {
+        let Segment {
+            inbox: _,
+            opt: _,
+            batcher: _,
+            user,
+            get_search_aggregator,
+            post_search_aggregator,
+            post_multi_search_aggregator,
+            post_facet_search_aggregator,
+            add_documents_aggregator,
+            delete_documents_aggregator,
+            update_documents_aggregator,
+            get_fetch_documents_aggregator,
+            post_fetch_documents_aggregator,
+            get_tasks_aggregator,
+            health_aggregator,
+        } = self;
+
+        if let Some(get_search) =
+            take(get_search_aggregator).into_event(&user, "Documents Searched GET")
+        {
             let _ = self.batcher.push(get_search).await;
         }
-        if let Some(post_search) = post_search {
+        if let Some(post_search) =
+            take(post_search_aggregator).into_event(&user, "Documents Searched POST")
+        {
             let _ = self.batcher.push(post_search).await;
         }
-        if let Some(post_multi_search) = post_multi_search {
+        if let Some(post_multi_search) = take(post_multi_search_aggregator)
+            .into_event(&user, "Documents Searched by Multi-Search POST")
+        {
             let _ = self.batcher.push(post_multi_search).await;
         }
-        if let Some(add_documents) = add_documents {
+        if let Some(post_facet_search) = take(post_facet_search_aggregator)
+            .into_event(&user, "Documents Searched by Facet-Search POST")
+        {
+            let _ = self.batcher.push(post_facet_search).await;
+        }
+        if let Some(add_documents) =
+            take(add_documents_aggregator).into_event(&user, "Documents Added")
+        {
             let _ = self.batcher.push(add_documents).await;
         }
-        if let Some(delete_documents) = delete_documents {
+        if let Some(delete_documents) =
+            take(delete_documents_aggregator).into_event(&user, "Documents Deleted")
+        {
             let _ = self.batcher.push(delete_documents).await;
         }
-        if let Some(update_documents) = update_documents {
+        if let Some(update_documents) =
+            take(update_documents_aggregator).into_event(&user, "Documents Updated")
+        {
             let _ = self.batcher.push(update_documents).await;
         }
-        if let Some(get_fetch_documents) = get_fetch_documents {
+        if let Some(get_fetch_documents) =
+            take(get_fetch_documents_aggregator).into_event(&user, "Documents Fetched GET") {
             let _ = self.batcher.push(get_fetch_documents).await;
         }
-        if let Some(post_fetch_documents) = post_fetch_documents {
+        if let Some(post_fetch_documents) =
+            take(post_fetch_documents_aggregator).into_event(&user, "Documents Fetched POST") {
             let _ = self.batcher.push(post_fetch_documents).await;
         }
-        if let Some(get_tasks) = get_tasks {
+        if let Some(get_tasks) = take(get_tasks_aggregator).into_event(&user, "Tasks Seen") {
             let _ = self.batcher.push(get_tasks).await;
         }
-        if let Some(health) = health {
+        if let Some(health) = take(health_aggregator).into_event(&user, "Health Seen") {
             let _ = self.batcher.push(health).await;
         }
         let _ = self.batcher.flush().await;
@@ -886,6 +914,144 @@ impl MultiSearchAggregator {
     }
 }
 
+#[derive(Default)]
+pub struct FacetSearchAggregator {
+    timestamp: Option<OffsetDateTime>,
+
+    // context
+    user_agents: HashSet<String>,
+
+    // requests
+    total_received: usize,
+    total_succeeded: usize,
+    time_spent: BinaryHeap<usize>,
+
+    // The set of all facetNames that were used
+    facet_names: HashSet<String>,
+
+    // As there been any other parameter than the facetName or facetQuery ones?
+    additional_search_parameters_provided: bool,
+}
+
+impl FacetSearchAggregator {
+    pub fn from_query(query: &FacetSearchQuery, request: &HttpRequest) -> Self {
+        let FacetSearchQuery {
+            facet_query: _,
+            facet_name,
+            q,
+            offset,
+            limit,
+            page,
+            hits_per_page,
+            attributes_to_retrieve,
+            attributes_to_crop,
+            crop_length,
+            attributes_to_highlight,
+            show_matches_position,
+            filter,
+            sort,
+            facets,
+            highlight_pre_tag,
+            highlight_post_tag,
+            crop_marker,
+            matching_strategy,
+        } = query;
+
+        let mut ret = Self::default();
+        ret.timestamp = Some(OffsetDateTime::now_utc());
+
+        ret.total_received = 1;
+        ret.user_agents = extract_user_agents(request).into_iter().collect();
+        ret.facet_names = Some(facet_name.clone()).into_iter().collect();
+
+        ret.additional_search_parameters_provided = q.is_some()
+            || *offset != DEFAULT_SEARCH_OFFSET()
+            || *limit != DEFAULT_SEARCH_LIMIT()
+            || page.is_some()
+            || hits_per_page.is_some()
+            || attributes_to_retrieve.is_some()
+            || attributes_to_crop.is_some()
+            || *crop_length != DEFAULT_CROP_LENGTH()
+            || attributes_to_highlight.is_some()
+            || *show_matches_position
+            || filter.is_some()
+            || sort.is_some()
+            || facets.is_some()
+            || *highlight_pre_tag != DEFAULT_HIGHLIGHT_PRE_TAG()
+            || *highlight_post_tag != DEFAULT_HIGHLIGHT_POST_TAG()
+            || *crop_marker != DEFAULT_CROP_MARKER()
+            || *matching_strategy != MatchingStrategy::default();
+
+        ret
+    }
+
+    pub fn succeed(&mut self, result: &FacetSearchResult) {
+        self.total_succeeded = self.total_succeeded.saturating_add(1);
+        self.time_spent.push(result.processing_time_ms as usize);
+    }
+
+    /// Aggregate one [SearchAggregator] into another.
+    pub fn aggregate(&mut self, mut other: Self) {
+        if self.timestamp.is_none() {
+            self.timestamp = other.timestamp;
+        }
+
+        // context
+        for user_agent in other.user_agents.into_iter() {
+            self.user_agents.insert(user_agent);
+        }
+
+        // request
+        self.total_received = self.total_received.saturating_add(other.total_received);
+        self.total_succeeded = self.total_succeeded.saturating_add(other.total_succeeded);
+        self.time_spent.append(&mut other.time_spent);
+
+        // facet_names
+        for facet_name in other.facet_names.into_iter() {
+            self.facet_names.insert(facet_name);
+        }
+
+        // additional_search_parameters_provided
+        self.additional_search_parameters_provided = self.additional_search_parameters_provided
+            | other.additional_search_parameters_provided;
+    }
+
+    pub fn into_event(self, user: &User, event_name: &str) -> Option<Track> {
+        if self.total_received == 0 {
+            None
+        } else {
+            // the index of the 99th percentage of value
+            let percentile_99th = 0.99 * (self.total_succeeded as f64 - 1.) + 1.;
+            // we get all the values in a sorted manner
+            let time_spent = self.time_spent.into_sorted_vec();
+            // We are only interested by the slowest value of the 99th fastest results
+            let time_spent = time_spent.get(percentile_99th as usize);
+
+            let properties = json!({
+                "user-agent": self.user_agents,
+                "requests": {
+                    "99th_response_time":  time_spent.map(|t| format!("{:.2}", t)),
+                    "total_succeeded": self.total_succeeded,
+                    "total_failed": self.total_received.saturating_sub(self.total_succeeded), // just to be sure we never panics
+                    "total_received": self.total_received,
+                },
+                "facets": {
+                    "total_distinct_facet_count": self.facet_names.len(),
+                },
+                "additional_search_parameters_provided": self.additional_search_parameters_provided,
+            });
+
+            Some(Track {
+                timestamp: self.timestamp,
+                user: user.clone(),
+                event: event_name.to_string(),
+                properties,
+                ..Default::default()
+            })
+        }
+    }
+}
+
 #[derive(Default)]
 pub struct DocumentsAggregator {
     timestamp: Option<OffsetDateTime>,

meilisearch/src/routes/indexes/facet_search.rs

@@ -0,0 +1,133 @@
+use std::collections::{BTreeSet, HashSet};
+
+use actix_web::web::Data;
+use actix_web::{web, HttpRequest, HttpResponse};
+use deserr::actix_web::AwebJson;
+use index_scheduler::IndexScheduler;
+use log::debug;
+use meilisearch_types::deserr::DeserrJsonError;
+use meilisearch_types::error::deserr_codes::*;
+use meilisearch_types::error::ResponseError;
+use meilisearch_types::index_uid::IndexUid;
+use serde_json::Value;
+
+use crate::analytics::{Analytics, FacetSearchAggregator};
+use crate::extractors::authentication::policies::*;
+use crate::extractors::authentication::GuardedData;
+use crate::search::{
+    add_search_rules, perform_facet_search, MatchingStrategy, SearchQuery, DEFAULT_CROP_LENGTH,
+    DEFAULT_CROP_MARKER, DEFAULT_HIGHLIGHT_POST_TAG, DEFAULT_HIGHLIGHT_PRE_TAG,
+    DEFAULT_SEARCH_LIMIT, DEFAULT_SEARCH_OFFSET,
+};
+
+pub fn configure(cfg: &mut web::ServiceConfig) {
+    cfg.service(web::resource("").route(web::post().to(search)));
+}
+
+// TODO improve the error messages
+#[derive(Debug, Clone, Default, PartialEq, Eq, deserr::Deserr)]
+#[deserr(error = DeserrJsonError, rename_all = camelCase, deny_unknown_fields)]
+pub struct FacetSearchQuery {
+    #[deserr(default, error = DeserrJsonError<InvalidFacetSearchQuery>)]
+    pub facet_query: Option<String>,
+    #[deserr(error = DeserrJsonError<MissingFacetSearchFacetName>, missing_field_error = DeserrJsonError::missing_facet_search_facet_name)]
+    pub facet_name: String,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchQ>)]
+    pub q: Option<String>,
+    #[deserr(default = DEFAULT_SEARCH_OFFSET(), error = DeserrJsonError<InvalidSearchOffset>)]
+    pub offset: usize,
+    #[deserr(default = DEFAULT_SEARCH_LIMIT(), error = DeserrJsonError<InvalidSearchLimit>)]
+    pub limit: usize,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchPage>)]
+    pub page: Option<usize>,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchHitsPerPage>)]
+    pub hits_per_page: Option<usize>,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchAttributesToRetrieve>)]
+    pub attributes_to_retrieve: Option<BTreeSet<String>>,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchAttributesToCrop>)]
+    pub attributes_to_crop: Option<Vec<String>>,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchCropLength>, default = DEFAULT_CROP_LENGTH())]
+    pub crop_length: usize,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchAttributesToHighlight>)]
+    pub attributes_to_highlight: Option<HashSet<String>>,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchShowMatchesPosition>, default)]
+    pub show_matches_position: bool,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchFilter>)]
+    pub filter: Option<Value>,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchSort>)]
+    pub sort: Option<Vec<String>>,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchFacets>)]
+    pub facets: Option<Vec<String>>,
+    #[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())]
+    pub highlight_post_tag: String,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchCropMarker>, default = DEFAULT_CROP_MARKER())]
+    pub crop_marker: String,
+    #[deserr(default, error = DeserrJsonError<InvalidSearchMatchingStrategy>, default)]
+    pub matching_strategy: MatchingStrategy,
+}
+
+pub async fn search(
+    index_scheduler: GuardedData<ActionPolicy<{ actions::SEARCH }>, Data<IndexScheduler>>,
+    index_uid: web::Path<String>,
+    params: AwebJson<FacetSearchQuery, DeserrJsonError>,
+    req: HttpRequest,
+    analytics: web::Data<dyn Analytics>,
+) -> Result<HttpResponse, ResponseError> {
+    let index_uid = IndexUid::try_from(index_uid.into_inner())?;
+
+    let query = params.into_inner();
+    debug!("facet search called with params: {:?}", query);
+
+    let mut aggregate = FacetSearchAggregator::from_query(&query, &req);
+
+    let facet_query = query.facet_query.clone();
+    let facet_name = query.facet_name.clone();
+    let mut search_query = SearchQuery::from(query);
+
+    // Tenant token search_rules.
+    if let Some(search_rules) = index_scheduler.filters().get_index_search_rules(&index_uid) {
+        add_search_rules(&mut search_query, search_rules);
+    }
+
+    let index = index_scheduler.index(&index_uid)?;
+    let search_result = tokio::task::spawn_blocking(move || {
+        perform_facet_search(&index, search_query, facet_query, facet_name)
+    })
+    .await?;
+
+    if let Ok(ref search_result) = search_result {
+        aggregate.succeed(search_result);
+    }
+    analytics.post_facet_search(aggregate);
+
+    let search_result = search_result?;
+
+    debug!("returns: {:?}", search_result);
+    Ok(HttpResponse::Ok().json(search_result))
+}
+
+impl From<FacetSearchQuery> for SearchQuery {
+    fn from(value: FacetSearchQuery) -> Self {
+        SearchQuery {
+            q: value.q,
+            offset: value.offset,
+            limit: value.limit,
+            page: value.page,
+            hits_per_page: value.hits_per_page,
+            attributes_to_retrieve: value.attributes_to_retrieve,
+            attributes_to_crop: value.attributes_to_crop,
+            crop_length: value.crop_length,
+            attributes_to_highlight: value.attributes_to_highlight,
+            show_matches_position: value.show_matches_position,
+            filter: value.filter,
+            sort: value.sort,
+            facets: value.facets,
+            highlight_pre_tag: value.highlight_pre_tag,
+            highlight_post_tag: value.highlight_post_tag,
+            crop_marker: value.crop_marker,
+            matching_strategy: value.matching_strategy,
+        }
+    }
+}

meilisearch/src/routes/indexes/mod.rs

@@ -24,6 +24,7 @@ use crate::extractors::authentication::{AuthenticationError, GuardedData};
 use crate::extractors::sequential_extractor::SeqHandler;
 
 pub mod documents;
+pub mod facet_search;
 pub mod search;
 pub mod settings;
 
@@ -44,6 +45,7 @@ pub fn configure(cfg: &mut web::ServiceConfig) {
             .service(web::resource("/stats").route(web::get().to(SeqHandler(get_index_stats))))
             .service(web::scope("/documents").configure(documents::configure))
             .service(web::scope("/search").configure(search::configure))
+            .service(web::scope("/facet-search").configure(facet_search::configure))
             .service(web::scope("/settings").configure(settings::configure)),
     );
 }

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,
-    DEFAULT_CROP_LENGTH, DEFAULT_CROP_MARKER, DEFAULT_HIGHLIGHT_POST_TAG,
-    DEFAULT_HIGHLIGHT_PRE_TAG, DEFAULT_SEARCH_LIMIT, DEFAULT_SEARCH_OFFSET,
+    add_search_rules, perform_search, MatchingStrategy, SearchQuery, DEFAULT_CROP_LENGTH,
+    DEFAULT_CROP_MARKER, DEFAULT_HIGHLIGHT_POST_TAG, DEFAULT_HIGHLIGHT_PRE_TAG,
+    DEFAULT_SEARCH_LIMIT, DEFAULT_SEARCH_OFFSET,
 };
 
 pub fn configure(cfg: &mut web::ServiceConfig) {
@@ -58,8 +58,6 @@ pub struct SearchQueryGet {
     show_matches_position: 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>)]
@@ -94,7 +92,6 @@ impl From<SearchQueryGet> for SearchQuery {
             sort: other.sort.map(|attr| fix_sort_query_parameters(&attr)),
             show_matches_position: other.show_matches_position.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/tasks.rs

@@ -730,7 +730,7 @@ mod tests {
             let err = deserr_query_params::<TaskDeletionOrCancelationQuery>(params).unwrap_err();
             snapshot!(meili_snap::json_string!(err), @r###"
             {
-              "message": "Invalid value in parameter `types`: `createIndex` is not a valid task type. Available types are `documentAdditionOrUpdate`, `documentDeletion`, `documentDeletionByFilter`, `settingsUpdate`, `indexCreation`, `indexDeletion`, `indexUpdate`, `indexSwap`, `taskCancelation`, `taskDeletion`, `dumpCreation`, `snapshotCreation`.",
+              "message": "Invalid value in parameter `types`: `createIndex` is not a valid task type. Available types are `documentAdditionOrUpdate`, `documentDeletion`, `settingsUpdate`, `indexCreation`, `indexDeletion`, `indexUpdate`, `indexSwap`, `taskCancelation`, `taskDeletion`, `dumpCreation`, `snapshotCreation`.",
               "code": "invalid_task_types",
               "type": "invalid_request",
               "link": "https://docs.meilisearch.com/errors#invalid_task_types"

meilisearch/src/search.rs

@@ -5,12 +5,12 @@ use std::time::Instant;
 
 use deserr::Deserr;
 use either::Either;
-use indexmap::IndexMap;
 use meilisearch_auth::IndexSearchRules;
 use meilisearch_types::deserr::DeserrJsonError;
 use meilisearch_types::error::deserr_codes::*;
+use meilisearch_types::heed::RoTxn;
 use meilisearch_types::index_uid::IndexUid;
-use meilisearch_types::milli::OrderBy;
+use meilisearch_types::milli::{FacetValueHit, SearchForFacetValues};
 use meilisearch_types::settings::DEFAULT_PAGINATION_MAX_TOTAL_HITS;
 use meilisearch_types::{milli, Document};
 use milli::tokenizer::TokenizerBuilder;
@@ -62,8 +62,6 @@ 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())]
@@ -115,8 +113,6 @@ 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())]
@@ -144,7 +140,6 @@ impl SearchQueryWithIndex {
             filter,
             sort,
             facets,
-            sort_facet_values_by,
             highlight_pre_tag,
             highlight_post_tag,
             crop_marker,
@@ -166,7 +161,6 @@ impl SearchQueryWithIndex {
                 filter,
                 sort,
                 facets,
-                sort_facet_values_by,
                 highlight_pre_tag,
                 highlight_post_tag,
                 crop_marker,
@@ -178,7 +172,7 @@ impl SearchQueryWithIndex {
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Deserr)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Deserr)]
 #[deserr(rename_all = camelCase)]
 pub enum MatchingStrategy {
     /// Remove query words from last to first
@@ -202,26 +196,6 @@ impl From<MatchingStrategy> for TermsMatchingStrategy {
     }
 }
 
-#[derive(Debug, Default, Clone, PartialEq, Eq, Deserr)]
-#[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,
-        }
-    }
-}
-
 #[derive(Debug, Clone, Serialize, PartialEq, Eq)]
 pub struct SearchHit {
     #[serde(flatten)]
@@ -241,7 +215,7 @@ pub struct SearchResult {
     #[serde(flatten)]
     pub hits_info: HitsInfo,
     #[serde(skip_serializing_if = "Option::is_none")]
-    pub facet_distribution: Option<BTreeMap<String, IndexMap<String, u64>>>,
+    pub facet_distribution: Option<BTreeMap<String, BTreeMap<String, u64>>>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub facet_stats: Option<BTreeMap<String, FacetStats>>,
 }
@@ -269,6 +243,14 @@ pub struct FacetStats {
     pub max: f64,
 }
 
+#[derive(Serialize, Debug, Clone, PartialEq)]
+#[serde(rename_all = "camelCase")]
+pub struct FacetSearchResult {
+    pub facet_hits: Vec<FacetValueHit>,
+    pub facet_query: Option<String>,
+    pub processing_time_ms: u128,
+}
+
 /// Incorporate search rules in search query
 pub fn add_search_rules(query: &mut SearchQuery, rules: IndexSearchRules) {
     query.filter = match (query.filter.take(), rules.filter) {
@@ -289,14 +271,12 @@ pub fn add_search_rules(query: &mut SearchQuery, rules: IndexSearchRules) {
     }
 }
 
-pub fn perform_search(
-    index: &Index,
-    query: SearchQuery,
-) -> Result<SearchResult, MeilisearchHttpError> {
-    let before_search = Instant::now();
-    let rtxn = index.read_txn()?;
-
-    let mut search = index.search(&rtxn);
+fn prepare_search<'t>(
+    index: &'t Index,
+    rtxn: &'t RoTxn,
+    query: &'t SearchQuery,
+) -> Result<(milli::Search<'t>, bool, usize, usize), MeilisearchHttpError> {
+    let mut search = index.search(rtxn);
 
     if let Some(ref query) = query.q {
         search.query(query);
@@ -306,7 +286,7 @@ pub fn perform_search(
     search.terms_matching_strategy(query.matching_strategy.into());
 
     let max_total_hits = index
-        .pagination_max_total_hits(&rtxn)
+        .pagination_max_total_hits(rtxn)
         .map_err(milli::Error::from)?
         .unwrap_or(DEFAULT_PAGINATION_MAX_TOTAL_HITS);
 
@@ -348,6 +328,19 @@ pub fn perform_search(
         search.sort_criteria(sort);
     }
 
+    Ok((search, is_finite_pagination, max_total_hits, offset))
+}
+
+pub fn perform_search(
+    index: &Index,
+    query: SearchQuery,
+) -> Result<SearchResult, MeilisearchHttpError> {
+    let before_search = Instant::now();
+    let rtxn = index.read_txn()?;
+
+    let (search, is_finite_pagination, max_total_hits, offset) =
+        prepare_search(index, &rtxn, &query)?;
+
     let milli::SearchResult { documents_ids, matching_words, candidates, .. } = search.execute()?;
 
     let fields_ids_map = index.fields_ids_map(&rtxn).unwrap();
@@ -479,10 +472,7 @@ pub fn perform_search(
             if fields.iter().all(|f| f != "*") {
                 facet_distribution.facets(fields);
             }
-            let distribution = facet_distribution
-                .candidates(candidates)
-                .order_by(query.sort_facet_values_by.map_or_else(Default::default, Into::into))
-                .execute()?;
+            let distribution = facet_distribution.candidates(candidates).execute()?;
             let stats = facet_distribution.compute_stats()?;
             (Some(distribution), Some(stats))
         }
@@ -504,6 +494,28 @@ pub fn perform_search(
     Ok(result)
 }
 
+pub fn perform_facet_search(
+    index: &Index,
+    search_query: SearchQuery,
+    facet_query: Option<String>,
+    facet_name: String,
+) -> Result<FacetSearchResult, MeilisearchHttpError> {
+    let before_search = Instant::now();
+    let rtxn = index.read_txn()?;
+
+    let (search, _, _, _) = prepare_search(index, &rtxn, &search_query)?;
+    let mut facet_search = SearchForFacetValues::new(facet_name, search);
+    if let Some(facet_query) = &facet_query {
+        facet_search.query(facet_query);
+    }
+
+    Ok(FacetSearchResult {
+        facet_hits: facet_search.execute()?,
+        facet_query,
+        processing_time_ms: before_search.elapsed().as_millis(),
+    })
+}
+
 fn insert_geo_distance(sorts: &[String], document: &mut Document) {
     lazy_static::lazy_static! {
         static ref GEO_REGEX: Regex =

meilisearch/tests/tasks/errors.rs

@@ -97,7 +97,7 @@ async fn task_bad_types() {
     snapshot!(code, @"400 Bad Request");
     snapshot!(json_string!(response), @r###"
     {
-      "message": "Invalid value in parameter `types`: `doggo` is not a valid task type. Available types are `documentAdditionOrUpdate`, `documentDeletion`, `documentDeletionByFilter`, `settingsUpdate`, `indexCreation`, `indexDeletion`, `indexUpdate`, `indexSwap`, `taskCancelation`, `taskDeletion`, `dumpCreation`, `snapshotCreation`.",
+      "message": "Invalid value in parameter `types`: `doggo` is not a valid task type. Available types are `documentAdditionOrUpdate`, `documentDeletion`, `settingsUpdate`, `indexCreation`, `indexDeletion`, `indexUpdate`, `indexSwap`, `taskCancelation`, `taskDeletion`, `dumpCreation`, `snapshotCreation`.",
       "code": "invalid_task_types",
       "type": "invalid_request",
       "link": "https://docs.meilisearch.com/errors#invalid_task_types"
@@ -108,7 +108,7 @@ async fn task_bad_types() {
     snapshot!(code, @"400 Bad Request");
     snapshot!(json_string!(response), @r###"
     {
-      "message": "Invalid value in parameter `types`: `doggo` is not a valid task type. Available types are `documentAdditionOrUpdate`, `documentDeletion`, `documentDeletionByFilter`, `settingsUpdate`, `indexCreation`, `indexDeletion`, `indexUpdate`, `indexSwap`, `taskCancelation`, `taskDeletion`, `dumpCreation`, `snapshotCreation`.",
+      "message": "Invalid value in parameter `types`: `doggo` is not a valid task type. Available types are `documentAdditionOrUpdate`, `documentDeletion`, `settingsUpdate`, `indexCreation`, `indexDeletion`, `indexUpdate`, `indexSwap`, `taskCancelation`, `taskDeletion`, `dumpCreation`, `snapshotCreation`.",
       "code": "invalid_task_types",
       "type": "invalid_request",
       "link": "https://docs.meilisearch.com/errors#invalid_task_types"
@@ -119,7 +119,7 @@ async fn task_bad_types() {
     snapshot!(code, @"400 Bad Request");
     snapshot!(json_string!(response), @r###"
     {
-      "message": "Invalid value in parameter `types`: `doggo` is not a valid task type. Available types are `documentAdditionOrUpdate`, `documentDeletion`, `documentDeletionByFilter`, `settingsUpdate`, `indexCreation`, `indexDeletion`, `indexUpdate`, `indexSwap`, `taskCancelation`, `taskDeletion`, `dumpCreation`, `snapshotCreation`.",
+      "message": "Invalid value in parameter `types`: `doggo` is not a valid task type. Available types are `documentAdditionOrUpdate`, `documentDeletion`, `settingsUpdate`, `indexCreation`, `indexDeletion`, `indexUpdate`, `indexSwap`, `taskCancelation`, `taskDeletion`, `dumpCreation`, `snapshotCreation`.",
       "code": "invalid_task_types",
       "type": "invalid_request",
       "link": "https://docs.meilisearch.com/errors#invalid_task_types"

milli/Cargo.toml

@@ -32,7 +32,6 @@ heed = { git = "https://github.com/meilisearch/heed", tag = "v0.12.6", default-f
     "lmdb",
     "sync-read-txn",
 ] }
-indexmap = { version = "1.9.3", features = ["serde"] }
 json-depth-checker = { path = "../json-depth-checker" }
 levenshtein_automata = { version = "0.2.1", features = ["fst_automaton"] }
 memmap2 = "0.5.10"

milli/src/error.rs

@@ -124,6 +124,16 @@ only composed of alphanumeric characters (a-z A-Z 0-9), hyphens (-) and undersco
         }
     )]
     InvalidSortableAttribute { field: String, valid_fields: BTreeSet<String> },
+    #[error("Attribute `{}` is not filterable. {}",
+        .field,
+        match .valid_fields.is_empty() {
+            true => "This index does not have configured filterable attributes.".to_string(),
+            false => format!("Available filterable attributes are: `{}`.",
+                    valid_fields.iter().map(AsRef::as_ref).collect::<Vec<&str>>().join(", ")
+                ),
+        }
+    )]
+    InvalidFacetSearchFacetName { field: String, valid_fields: BTreeSet<String> },
     #[error("{}", HeedError::BadOpenOptions)]
     InvalidLmdbOpenOptions,
     #[error("You must specify where `sort` is listed in the rankingRules setting to use the sort parameter at search time.")]

milli/src/heed_codec/fst_set_codec.rs

@@ -0,0 +1,23 @@
+use std::borrow::Cow;
+
+use fst::Set;
+use heed::{BytesDecode, BytesEncode};
+
+/// A codec for values of type `Set<&[u8]>`.
+pub struct FstSetCodec;
+
+impl<'a> BytesEncode<'a> for FstSetCodec {
+    type EItem = Set<Vec<u8>>;
+
+    fn bytes_encode(item: &'a Self::EItem) -> Option<Cow<'a, [u8]>> {
+        Some(Cow::Borrowed(item.as_fst().as_bytes()))
+    }
+}
+
+impl<'a> BytesDecode<'a> for FstSetCodec {
+    type DItem = Set<&'a [u8]>;
+
+    fn bytes_decode(bytes: &'a [u8]) -> Option<Self::DItem> {
+        Set::new(bytes).ok()
+    }
+}

milli/src/heed_codec/mod.rs

@@ -2,6 +2,7 @@ mod beu32_str_codec;
 mod byte_slice_ref;
 pub mod facet;
 mod field_id_word_count_codec;
+mod fst_set_codec;
 mod obkv_codec;
 mod roaring_bitmap;
 mod roaring_bitmap_length;
@@ -15,6 +16,7 @@ pub use str_ref::StrRefCodec;
 
 pub use self::beu32_str_codec::BEU32StrCodec;
 pub use self::field_id_word_count_codec::FieldIdWordCountCodec;
+pub use self::fst_set_codec::FstSetCodec;
 pub use self::obkv_codec::ObkvCodec;
 pub use self::roaring_bitmap::{BoRoaringBitmapCodec, CboRoaringBitmapCodec, RoaringBitmapCodec};
 pub use self::roaring_bitmap_length::{

milli/src/index.rs

@@ -19,7 +19,7 @@ use crate::heed_codec::facet::{
     FacetGroupKeyCodec, FacetGroupValueCodec, FieldDocIdFacetF64Codec, FieldDocIdFacetStringCodec,
     FieldIdCodec, OrderedF64Codec,
 };
-use crate::heed_codec::{ScriptLanguageCodec, StrBEU16Codec, StrRefCodec};
+use crate::heed_codec::{FstSetCodec, ScriptLanguageCodec, StrBEU16Codec, StrRefCodec};
 use crate::{
     default_criteria, BEU32StrCodec, BoRoaringBitmapCodec, CboRoaringBitmapCodec, Criterion,
     DocumentId, ExternalDocumentsIds, FacetDistribution, FieldDistribution, FieldId,
@@ -85,6 +85,7 @@ pub mod db_name {
     pub const FACET_ID_IS_NULL_DOCIDS: &str = "facet-id-is-null-docids";
     pub const FACET_ID_IS_EMPTY_DOCIDS: &str = "facet-id-is-empty-docids";
     pub const FACET_ID_STRING_DOCIDS: &str = "facet-id-string-docids";
+    pub const FACET_ID_STRING_FST: &str = "facet-id-string-fst";
     pub const FIELD_ID_DOCID_FACET_F64S: &str = "field-id-docid-facet-f64s";
     pub const FIELD_ID_DOCID_FACET_STRINGS: &str = "field-id-docid-facet-strings";
     pub const DOCUMENTS: &str = "documents";
@@ -147,6 +148,8 @@ pub struct Index {
     pub facet_id_f64_docids: Database<FacetGroupKeyCodec<OrderedF64Codec>, FacetGroupValueCodec>,
     /// Maps the facet field id and ranges of strings with the docids that corresponds to them.
     pub facet_id_string_docids: Database<FacetGroupKeyCodec<StrRefCodec>, FacetGroupValueCodec>,
+    /// Maps the facet field id of the string facets with an FST containing all the facets values.
+    pub facet_id_string_fst: Database<OwnedType<BEU16>, FstSetCodec>,
 
     /// Maps the document id, the facet field id and the numbers.
     pub field_id_docid_facet_f64s: Database<FieldDocIdFacetF64Codec, Unit>,
@@ -166,7 +169,7 @@ impl Index {
     ) -> Result<Index> {
         use db_name::*;
 
-        options.max_dbs(23);
+        options.max_dbs(24);
         unsafe { options.flag(Flags::MdbAlwaysFreePages) };
 
         let env = options.open(path)?;
@@ -197,13 +200,13 @@ impl Index {
         let facet_id_f64_docids = env.create_database(&mut wtxn, Some(FACET_ID_F64_DOCIDS))?;
         let facet_id_string_docids =
             env.create_database(&mut wtxn, Some(FACET_ID_STRING_DOCIDS))?;
+        let facet_id_string_fst = env.create_database(&mut wtxn, Some(FACET_ID_STRING_FST))?;
         let facet_id_exists_docids =
             env.create_database(&mut wtxn, Some(FACET_ID_EXISTS_DOCIDS))?;
         let facet_id_is_null_docids =
             env.create_database(&mut wtxn, Some(FACET_ID_IS_NULL_DOCIDS))?;
         let facet_id_is_empty_docids =
             env.create_database(&mut wtxn, Some(FACET_ID_IS_EMPTY_DOCIDS))?;
-
         let field_id_docid_facet_f64s =
             env.create_database(&mut wtxn, Some(FIELD_ID_DOCID_FACET_F64S))?;
         let field_id_docid_facet_strings =
@@ -232,6 +235,7 @@ impl Index {
             field_id_word_count_docids,
             facet_id_f64_docids,
             facet_id_string_docids,
+            facet_id_string_fst,
             facet_id_exists_docids,
             facet_id_is_null_docids,
             facet_id_is_empty_docids,

milli/src/lib.rs

@@ -99,8 +99,9 @@ pub use self::heed_codec::{
 };
 pub use self::index::Index;
 pub use self::search::{
-    FacetDistribution, Filter, FormatOptions, MatchBounds, MatcherBuilder, MatchingWords, OrderBy,
-    Search, SearchResult, TermsMatchingStrategy, DEFAULT_VALUES_PER_FACET,
+    FacetDistribution, FacetValueHit, Filter, FormatOptions, MatchBounds, MatcherBuilder,
+    MatchingWords, Search, SearchForFacetValues, SearchResult, TermsMatchingStrategy,
+    DEFAULT_VALUES_PER_FACET,
 };
 
 pub type Result<T> = std::result::Result<T, error::Error>;

milli/src/search/facet/facet_distribution.rs

@@ -4,18 +4,16 @@ use std::{fmt, mem};
 
 use heed::types::ByteSlice;
 use heed::BytesDecode;
-use indexmap::IndexMap;
 use roaring::RoaringBitmap;
 
 use crate::error::UserError;
 use crate::facet::FacetType;
 use crate::heed_codec::facet::{
-    FacetGroupKeyCodec, FieldDocIdFacetF64Codec, FieldDocIdFacetStringCodec, OrderedF64Codec,
+    FacetGroupKeyCodec, FacetGroupValueCodec, FieldDocIdFacetF64Codec, FieldDocIdFacetStringCodec,
+    OrderedF64Codec,
 };
 use crate::heed_codec::{ByteSliceRefCodec, StrRefCodec};
-use crate::search::facet::facet_distribution_iter::{
-    count_iterate_over_facet_distribution, lexicographically_iterate_over_facet_distribution,
-};
+use crate::search::facet::facet_distribution_iter;
 use crate::{FieldId, Index, Result};
 
 /// The default number of values by facets that will
@@ -26,21 +24,10 @@ pub const DEFAULT_VALUES_PER_FACET: usize = 100;
 /// the system to choose between one algorithm or another.
 const CANDIDATES_THRESHOLD: u64 = 3000;
 
-/// How should we fetch the facets?
-#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub enum OrderBy {
-    /// By lexicographic order...
-    #[default]
-    Lexicographic,
-    /// Or by number of docids in common?
-    Count,
-}
-
 pub struct FacetDistribution<'a> {
     facets: Option<HashSet<String>>,
     candidates: Option<RoaringBitmap>,
     max_values_per_facet: usize,
-    order_by: OrderBy,
     rtxn: &'a heed::RoTxn<'a>,
     index: &'a Index,
 }
@@ -51,7 +38,6 @@ impl<'a> FacetDistribution<'a> {
             facets: None,
             candidates: None,
             max_values_per_facet: DEFAULT_VALUES_PER_FACET,
-            order_by: OrderBy::default(),
             rtxn,
             index,
         }
@@ -67,11 +53,6 @@ impl<'a> FacetDistribution<'a> {
         self
     }
 
-    pub fn order_by(&mut self, order_by: OrderBy) -> &mut Self {
-        self.order_by = order_by;
-        self
-    }
-
     pub fn candidates(&mut self, candidates: RoaringBitmap) -> &mut Self {
         self.candidates = Some(candidates);
         self
@@ -84,7 +65,7 @@ impl<'a> FacetDistribution<'a> {
         field_id: FieldId,
         facet_type: FacetType,
         candidates: &RoaringBitmap,
-        distribution: &mut IndexMap<String, u64>,
+        distribution: &mut BTreeMap<String, u64>,
     ) -> heed::Result<()> {
         match facet_type {
             FacetType::Number => {
@@ -153,15 +134,9 @@ impl<'a> FacetDistribution<'a> {
         &self,
         field_id: FieldId,
         candidates: &RoaringBitmap,
-        order_by: OrderBy,
-        distribution: &mut IndexMap<String, u64>,
+        distribution: &mut BTreeMap<String, u64>,
     ) -> heed::Result<()> {
-        let search_function = match order_by {
-            OrderBy::Lexicographic => lexicographically_iterate_over_facet_distribution,
-            OrderBy::Count => count_iterate_over_facet_distribution,
-        };
-
-        search_function(
+        facet_distribution_iter::iterate_over_facet_distribution(
             self.rtxn,
             self.index
                 .facet_id_f64_docids
@@ -184,15 +159,9 @@ impl<'a> FacetDistribution<'a> {
         &self,
         field_id: FieldId,
         candidates: &RoaringBitmap,
-        order_by: OrderBy,
-        distribution: &mut IndexMap<String, u64>,
+        distribution: &mut BTreeMap<String, u64>,
     ) -> heed::Result<()> {
-        let search_function = match order_by {
-            OrderBy::Lexicographic => lexicographically_iterate_over_facet_distribution,
-            OrderBy::Count => count_iterate_over_facet_distribution,
-        };
-
-        search_function(
+        facet_distribution_iter::iterate_over_facet_distribution(
             self.rtxn,
             self.index
                 .facet_id_string_docids
@@ -220,46 +189,95 @@ impl<'a> FacetDistribution<'a> {
         )
     }
 
-    fn facet_values(&self, field_id: FieldId) -> heed::Result<IndexMap<String, u64>> {
-        use FacetType::{Number, String};
+    /// Placeholder search, a.k.a. no candidates were specified. We iterate throught the
+    /// facet values one by one and iterate on the facet level 0 for numbers.
+    fn facet_values_from_raw_facet_database(
+        &self,
+        field_id: FieldId,
+    ) -> heed::Result<BTreeMap<String, u64>> {
+        let mut distribution = BTreeMap::new();
 
-        let mut distribution = IndexMap::new();
-        match (self.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.
-                self.facet_distribution_from_documents(field_id, Number, cnd, &mut distribution)?;
-                self.facet_distribution_from_documents(field_id, String, cnd, &mut distribution)?;
-            }
-            _ => {
-                let universe;
-                let candidates;
-                match &self.candidates {
-                    Some(cnd) => candidates = cnd,
-                    None => {
-                        universe = self.index.documents_ids(self.rtxn)?;
-                        candidates = &universe;
-                    }
-                }
+        let db = self.index.facet_id_f64_docids;
+        let mut prefix = vec![];
+        prefix.extend_from_slice(&field_id.to_be_bytes());
+        prefix.push(0); // read values from level 0 only
 
-                self.facet_numbers_distribution_from_facet_levels(
-                    field_id,
-                    candidates,
-                    self.order_by,
-                    &mut distribution,
-                )?;
-                self.facet_strings_distribution_from_facet_levels(
-                    field_id,
-                    candidates,
-                    self.order_by,
-                    &mut distribution,
-                )?;
+        let iter = db
+            .as_polymorph()
+            .prefix_iter::<_, ByteSlice, ByteSlice>(self.rtxn, prefix.as_slice())?
+            .remap_types::<FacetGroupKeyCodec<OrderedF64Codec>, FacetGroupValueCodec>();
+
+        for result in iter {
+            let (key, value) = result?;
+            distribution.insert(key.left_bound.to_string(), value.bitmap.len());
+            if distribution.len() == self.max_values_per_facet {
+                break;
             }
-        };
+        }
+
+        let iter = self
+            .index
+            .facet_id_string_docids
+            .as_polymorph()
+            .prefix_iter::<_, ByteSlice, ByteSlice>(self.rtxn, prefix.as_slice())?
+            .remap_types::<FacetGroupKeyCodec<StrRefCodec>, FacetGroupValueCodec>();
+
+        for result in iter {
+            let (key, value) = result?;
+
+            let docid = value.bitmap.iter().next().unwrap();
+            let key: (FieldId, _, &'a str) = (field_id, docid, key.left_bound);
+            let original_string =
+                self.index.field_id_docid_facet_strings.get(self.rtxn, &key)?.unwrap().to_owned();
+
+            distribution.insert(original_string, value.bitmap.len());
+            if distribution.len() == self.max_values_per_facet {
+                break;
+            }
+        }
 
         Ok(distribution)
     }
 
+    fn facet_values(&self, field_id: FieldId) -> heed::Result<BTreeMap<String, u64>> {
+        use FacetType::{Number, String};
+
+        match self.candidates {
+            Some(ref candidates) => {
+                // 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.
+                let mut distribution = BTreeMap::new();
+                if candidates.len() <= CANDIDATES_THRESHOLD {
+                    self.facet_distribution_from_documents(
+                        field_id,
+                        Number,
+                        candidates,
+                        &mut distribution,
+                    )?;
+                    self.facet_distribution_from_documents(
+                        field_id,
+                        String,
+                        candidates,
+                        &mut distribution,
+                    )?;
+                } else {
+                    self.facet_numbers_distribution_from_facet_levels(
+                        field_id,
+                        candidates,
+                        &mut distribution,
+                    )?;
+                    self.facet_strings_distribution_from_facet_levels(
+                        field_id,
+                        candidates,
+                        &mut distribution,
+                    )?;
+                }
+                Ok(distribution)
+            }
+            None => self.facet_values_from_raw_facet_database(field_id),
+        }
+    }
+
     pub fn compute_stats(&self) -> Result<BTreeMap<String, (f64, f64)>> {
         let fields_ids_map = self.index.fields_ids_map(self.rtxn)?;
         let filterable_fields = self.index.filterable_fields(self.rtxn)?;
@@ -319,7 +337,7 @@ impl<'a> FacetDistribution<'a> {
         Ok(distribution)
     }
 
-    pub fn execute(&self) -> Result<BTreeMap<String, IndexMap<String, u64>>> {
+    pub fn execute(&self) -> Result<BTreeMap<String, BTreeMap<String, u64>>> {
         let fields_ids_map = self.index.fields_ids_map(self.rtxn)?;
         let filterable_fields = self.index.filterable_fields(self.rtxn)?;
 
@@ -356,20 +374,13 @@ impl<'a> FacetDistribution<'a> {
 
 impl fmt::Debug for FacetDistribution<'_> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        let FacetDistribution {
-            facets,
-            candidates,
-            max_values_per_facet,
-            order_by,
-            rtxn: _,
-            index: _,
-        } = self;
+        let FacetDistribution { facets, candidates, max_values_per_facet, rtxn: _, index: _ } =
+            self;
 
         f.debug_struct("FacetDistribution")
             .field("facets", facets)
             .field("candidates", candidates)
             .field("max_values_per_facet", max_values_per_facet)
-            .field("order_by", order_by)
             .finish()
     }
 }

milli/src/search/facet/facet_distribution_iter.rs

@@ -1,5 +1,3 @@
-use std::cmp::Reverse;
-use std::collections::BinaryHeap;
 use std::ops::ControlFlow;
 
 use heed::Result;
@@ -21,7 +19,7 @@ use crate::DocumentId;
 ///
 /// The return value of the closure is a `ControlFlow<()>` which indicates whether we should
 /// keep iterating over the different facet values or stop.
-pub fn lexicographically_iterate_over_facet_distribution<'t, CB>(
+pub fn iterate_over_facet_distribution<'t, CB>(
     rtxn: &'t heed::RoTxn<'t>,
     db: heed::Database<FacetGroupKeyCodec<ByteSliceRefCodec>, FacetGroupValueCodec>,
     field_id: u16,
@@ -31,7 +29,7 @@ pub fn lexicographically_iterate_over_facet_distribution<'t, CB>(
 where
     CB: FnMut(&'t [u8], u64, DocumentId) -> Result<ControlFlow<()>>,
 {
-    let mut fd = LexicographicFacetDistribution { rtxn, db, field_id, callback };
+    let mut fd = FacetDistribution { rtxn, db, field_id, callback };
     let highest_level = get_highest_level(
         rtxn,
         db.remap_key_type::<FacetGroupKeyCodec<ByteSliceRefCodec>>(),
@@ -46,99 +44,7 @@ where
     }
 }
 
-pub fn count_iterate_over_facet_distribution<'t, CB>(
-    rtxn: &'t heed::RoTxn<'t>,
-    db: heed::Database<FacetGroupKeyCodec<ByteSliceRefCodec>, FacetGroupValueCodec>,
-    field_id: u16,
-    candidates: &RoaringBitmap,
-    mut callback: CB,
-) -> Result<()>
-where
-    CB: FnMut(&'t [u8], u64, DocumentId) -> Result<ControlFlow<()>>,
-{
-    #[derive(Debug, PartialOrd, Ord, PartialEq, Eq)]
-    struct LevelEntry<'t> {
-        /// The number of candidates in this entry.
-        count: u64,
-        /// The key level of the entry.
-        level: Reverse<u8>,
-        /// The left bound key.
-        left_bound: &'t [u8],
-        /// The number of keys we must look for after `left_bound`.
-        group_size: u8,
-        /// Any docid in the set of matching documents. Used to find the original facet string.
-        any_docid: u32,
-    }
-
-    // Represents the list of keys that we must explore.
-    let mut heap = BinaryHeap::new();
-    let highest_level = get_highest_level(
-        rtxn,
-        db.remap_key_type::<FacetGroupKeyCodec<ByteSliceRefCodec>>(),
-        field_id,
-    )?;
-
-    if let Some(first_bound) = get_first_facet_value::<ByteSliceRefCodec>(rtxn, db, field_id)? {
-        // We first fill the heap with values from the highest level
-        let starting_key =
-            FacetGroupKey { field_id, level: highest_level, left_bound: first_bound };
-        for el in db.range(rtxn, &(&starting_key..)).unwrap().take(usize::MAX) {
-            let (key, value) = el.unwrap();
-            // The range is unbounded on the right and the group size for the highest level is MAX,
-            // so we need to check that we are not iterating over the next field id
-            if key.field_id != field_id {
-                break;
-            }
-            let intersection = value.bitmap & candidates;
-            let count = intersection.len();
-            if count != 0 {
-                heap.push(LevelEntry {
-                    count,
-                    level: Reverse(key.level),
-                    left_bound: key.left_bound,
-                    group_size: value.size,
-                    any_docid: intersection.min().unwrap(),
-                });
-            }
-        }
-
-        while let Some(LevelEntry { count, level, left_bound, group_size, any_docid }) = heap.pop()
-        {
-            if let Reverse(0) = level {
-                match (callback)(left_bound, count, any_docid)? {
-                    ControlFlow::Continue(_) => (),
-                    ControlFlow::Break(_) => return Ok(()),
-                }
-            } else {
-                let starting_key = FacetGroupKey { field_id, level: level.0 - 1, left_bound };
-                for el in db.range(rtxn, &(&starting_key..)).unwrap().take(group_size as usize) {
-                    let (key, value) = el.unwrap();
-                    // The range is unbounded on the right and the group size for the highest level is MAX,
-                    // so we need to check that we are not iterating over the next field id
-                    if key.field_id != field_id {
-                        break;
-                    }
-                    let intersection = value.bitmap & candidates;
-                    let count = intersection.len();
-                    if count != 0 {
-                        heap.push(LevelEntry {
-                            count,
-                            level: Reverse(key.level),
-                            left_bound: key.left_bound,
-                            group_size: value.size,
-                            any_docid: intersection.min().unwrap(),
-                        });
-                    }
-                }
-            }
-        }
-    }
-
-    Ok(())
-}
-
-/// Iterate over the facets values by lexicographic order.
-struct LexicographicFacetDistribution<'t, CB>
+struct FacetDistribution<'t, CB>
 where
     CB: FnMut(&'t [u8], u64, DocumentId) -> Result<ControlFlow<()>>,
 {
@@ -148,7 +54,7 @@ where
     callback: CB,
 }
 
-impl<'t, CB> LexicographicFacetDistribution<'t, CB>
+impl<'t, CB> FacetDistribution<'t, CB>
 where
     CB: FnMut(&'t [u8], u64, DocumentId) -> Result<ControlFlow<()>>,
 {
@@ -180,7 +86,6 @@ where
         }
         Ok(ControlFlow::Continue(()))
     }
-
     fn iterate(
         &mut self,
         candidates: &RoaringBitmap,
@@ -211,7 +116,7 @@ where
                     value.size as usize,
                 )?;
                 match cf {
-                    ControlFlow::Continue(_) => (),
+                    ControlFlow::Continue(_) => {}
                     ControlFlow::Break(_) => return Ok(ControlFlow::Break(())),
                 }
             }
@@ -227,7 +132,7 @@ mod tests {
     use heed::BytesDecode;
     use roaring::RoaringBitmap;
 
-    use super::lexicographically_iterate_over_facet_distribution;
+    use super::iterate_over_facet_distribution;
     use crate::heed_codec::facet::OrderedF64Codec;
     use crate::milli_snap;
     use crate::search::facet::tests::{get_random_looking_index, get_simple_index};
@@ -239,7 +144,7 @@ mod tests {
             let txn = index.env.read_txn().unwrap();
             let candidates = (0..=255).collect::<RoaringBitmap>();
             let mut results = String::new();
-            lexicographically_iterate_over_facet_distribution(
+            iterate_over_facet_distribution(
                 &txn,
                 index.content,
                 0,
@@ -256,7 +161,6 @@ mod tests {
             txn.commit().unwrap();
         }
     }
-
     #[test]
     fn filter_distribution_all_stop_early() {
         let indexes = [get_simple_index(), get_random_looking_index()];
@@ -265,7 +169,7 @@ mod tests {
             let candidates = (0..=255).collect::<RoaringBitmap>();
             let mut results = String::new();
             let mut nbr_facets = 0;
-            lexicographically_iterate_over_facet_distribution(
+            iterate_over_facet_distribution(
                 &txn,
                 index.content,
                 0,

milli/src/search/facet/mod.rs

@@ -4,7 +4,7 @@ use heed::types::{ByteSlice, DecodeIgnore};
 use heed::{BytesDecode, RoTxn};
 use roaring::RoaringBitmap;
 
-pub use self::facet_distribution::{FacetDistribution, OrderBy, DEFAULT_VALUES_PER_FACET};
+pub use self::facet_distribution::{FacetDistribution, DEFAULT_VALUES_PER_FACET};
 pub use self::filter::{BadGeoError, Filter};
 use crate::heed_codec::facet::{FacetGroupKeyCodec, FacetGroupValueCodec, OrderedF64Codec};
 use crate::heed_codec::ByteSliceRefCodec;

milli/src/search/mod.rs

@@ -1,14 +1,19 @@
 use std::fmt;
 
+use fst::automaton::{Automaton, Str};
+use fst::{IntoStreamer, Streamer};
 use levenshtein_automata::{LevenshteinAutomatonBuilder as LevBuilder, DFA};
+use log::error;
 use once_cell::sync::Lazy;
 use roaring::bitmap::RoaringBitmap;
 
-pub use self::facet::{FacetDistribution, Filter, OrderBy, DEFAULT_VALUES_PER_FACET};
+pub use self::facet::{FacetDistribution, Filter, DEFAULT_VALUES_PER_FACET};
 pub use self::new::matches::{FormatOptions, MatchBounds, Matcher, MatcherBuilder, MatchingWords};
 use self::new::PartialSearchResult;
+use crate::error::UserError;
+use crate::heed_codec::facet::{FacetGroupKey, FacetGroupValue};
 use crate::{
-    execute_search, AscDesc, DefaultSearchLogger, DocumentId, Index, Result, SearchContext,
+    execute_search, AscDesc, DefaultSearchLogger, DocumentId, Index, Result, SearchContext, BEU16,
 };
 
 // Building these factories is not free.
@@ -16,6 +21,9 @@ static LEVDIST0: Lazy<LevBuilder> = Lazy::new(|| LevBuilder::new(0, true));
 static LEVDIST1: Lazy<LevBuilder> = Lazy::new(|| LevBuilder::new(1, true));
 static LEVDIST2: Lazy<LevBuilder> = Lazy::new(|| LevBuilder::new(2, true));
 
+/// The maximum number of facets returned by the facet search route.
+const MAX_NUMBER_OF_FACETS: usize = 100;
+
 pub mod facet;
 mod fst_utils;
 pub mod new;
@@ -199,6 +207,170 @@ pub fn build_dfa(word: &str, typos: u8, is_prefix: bool) -> DFA {
     }
 }
 
+pub struct SearchForFacetValues<'a> {
+    query: Option<String>,
+    facet: String,
+    search_query: Search<'a>,
+}
+
+impl<'a> SearchForFacetValues<'a> {
+    pub fn new(facet: String, search_query: Search<'a>) -> SearchForFacetValues<'a> {
+        SearchForFacetValues { query: None, facet, search_query }
+    }
+
+    pub fn query(&mut self, query: impl Into<String>) -> &mut Self {
+        self.query = Some(query.into());
+        self
+    }
+
+    pub fn execute(&self) -> Result<Vec<FacetValueHit>> {
+        let index = self.search_query.index;
+        let rtxn = self.search_query.rtxn;
+
+        let filterable_fields = index.filterable_fields(rtxn)?;
+        if !filterable_fields.contains(&self.facet) {
+            return Err(UserError::InvalidFacetSearchFacetName {
+                field: self.facet.clone(),
+                valid_fields: filterable_fields.into_iter().collect(),
+            }
+            .into());
+        }
+
+        let fields_ids_map = index.fields_ids_map(rtxn)?;
+        let fid = match fields_ids_map.id(&self.facet) {
+            Some(fid) => fid,
+            // we return an empty list of results when the attribute has been
+            // set as filterable but no document contains this field (yet).
+            None => return Ok(Vec::new()),
+        };
+
+        let fst = match self.search_query.index.facet_id_string_fst.get(rtxn, &BEU16::new(fid))? {
+            Some(fst) => fst,
+            None => return Ok(vec![]),
+        };
+
+        let search_candidates = self.search_query.execute()?.candidates;
+
+        match self.query.as_ref() {
+            Some(query) => {
+                let authorize_typos = self.search_query.index.authorize_typos(rtxn)?;
+                let field_authorizes_typos =
+                    !self.search_query.index.exact_attributes_ids(rtxn)?.contains(&fid);
+
+                if authorize_typos && field_authorizes_typos {
+                    let mut results = vec![];
+
+                    let exact_words_fst = self.search_query.index.exact_words(rtxn)?;
+                    if exact_words_fst.map_or(false, |fst| fst.contains(query)) {
+                        let key =
+                            FacetGroupKey { field_id: fid, level: 0, left_bound: query.as_ref() };
+                        if let Some(FacetGroupValue { bitmap, .. }) =
+                            index.facet_id_string_docids.get(rtxn, &key)?
+                        {
+                            let count = search_candidates.intersection_len(&bitmap);
+                            if count != 0 {
+                                results.push(FacetValueHit { value: query.to_string(), count });
+                            }
+                        }
+                    } else {
+                        let one_typo = self.search_query.index.min_word_len_one_typo(rtxn)?;
+                        let two_typos = self.search_query.index.min_word_len_two_typos(rtxn)?;
+
+                        let is_prefix = true;
+                        let automaton = if query.len() < one_typo as usize {
+                            build_dfa(query, 0, is_prefix)
+                        } else if query.len() < two_typos as usize {
+                            build_dfa(query, 1, is_prefix)
+                        } else {
+                            build_dfa(query, 2, is_prefix)
+                        };
+
+                        let mut stream = fst.search(automaton).into_stream();
+                        let mut length = 0;
+                        while let Some(facet_value) = stream.next() {
+                            let value = std::str::from_utf8(facet_value)?;
+                            let key = FacetGroupKey { field_id: fid, level: 0, left_bound: value };
+                            let docids = match index.facet_id_string_docids.get(rtxn, &key)? {
+                                Some(FacetGroupValue { bitmap, .. }) => bitmap,
+                                None => {
+                                    error!(
+                                        "the facet value is missing from the facet database: {key:?}"
+                                    );
+                                    continue;
+                                }
+                            };
+                            let count = search_candidates.intersection_len(&docids);
+                            if count != 0 {
+                                results.push(FacetValueHit { value: value.to_string(), count });
+                                length += 1;
+                            }
+                            if length >= MAX_NUMBER_OF_FACETS {
+                                break;
+                            }
+                        }
+                    }
+
+                    Ok(results)
+                } else {
+                    let automaton = Str::new(query).starts_with();
+                    let mut stream = fst.search(automaton).into_stream();
+                    let mut results = vec![];
+                    let mut length = 0;
+                    while let Some(facet_value) = stream.next() {
+                        let value = std::str::from_utf8(facet_value)?;
+                        let key = FacetGroupKey { field_id: fid, level: 0, left_bound: value };
+                        let docids = match index.facet_id_string_docids.get(rtxn, &key)? {
+                            Some(FacetGroupValue { bitmap, .. }) => bitmap,
+                            None => {
+                                error!(
+                                    "the facet value is missing from the facet database: {key:?}"
+                                );
+                                continue;
+                            }
+                        };
+                        let count = search_candidates.intersection_len(&docids);
+                        if count != 0 {
+                            results.push(FacetValueHit { value: value.to_string(), count });
+                            length += 1;
+                        }
+                        if length >= MAX_NUMBER_OF_FACETS {
+                            break;
+                        }
+                    }
+
+                    Ok(results)
+                }
+            }
+            None => {
+                let mut results = vec![];
+                let mut length = 0;
+                let prefix = FacetGroupKey { field_id: fid, level: 0, left_bound: "" };
+                for result in index.facet_id_string_docids.prefix_iter(rtxn, &prefix)? {
+                    let (FacetGroupKey { left_bound, .. }, FacetGroupValue { bitmap, .. }) =
+                        result?;
+                    let count = search_candidates.intersection_len(&bitmap);
+                    if count != 0 {
+                        results.push(FacetValueHit { value: left_bound.to_string(), count });
+                        length += 1;
+                    }
+                    if length >= MAX_NUMBER_OF_FACETS {
+                        break;
+                    }
+                }
+                Ok(results)
+            }
+        }
+    }
+}
+
+#[derive(Debug, Clone, serde::Serialize, PartialEq)]
+pub struct FacetValueHit {
+    /// The original facet value
+    pub value: String,
+    /// The number of documents associated to this facet
+    pub count: u64,
+}
+
 #[cfg(test)]
 mod test {
     #[allow(unused_imports)]

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

@@ -77,13 +77,9 @@ pub fn located_query_terms_from_tokens(
                 }
             }
             TokenKind::Separator(separator_kind) => {
-                match separator_kind {
-                    SeparatorKind::Hard => {
-                        position += 1;
-                    }
-                    SeparatorKind::Soft => {
-                        position += 0;
-                    }
+                // add penalty for hard separators
+                if let SeparatorKind::Hard = separator_kind {
+                    position = position.wrapping_add(1);
                 }
 
                 phrase = 'phrase: {
@@ -288,3 +284,36 @@ impl PhraseBuilder {
         })
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use charabia::TokenizerBuilder;
+
+    use super::*;
+    use crate::index::tests::TempIndex;
+
+    fn temp_index_with_documents() -> TempIndex {
+        let temp_index = TempIndex::new();
+        temp_index
+            .add_documents(documents!([
+                { "id": 1, "name": "split this world westfali westfalia the Ŵôřlḑôle" },
+                { "id": 2, "name": "Westfália" },
+                { "id": 3, "name": "Ŵôřlḑôle" },
+            ]))
+            .unwrap();
+        temp_index
+    }
+
+    #[test]
+    fn start_with_hard_separator() -> Result<()> {
+        let tokenizer = TokenizerBuilder::new().build();
+        let tokens = tokenizer.tokenize(".");
+        let index = temp_index_with_documents();
+        let rtxn = index.read_txn()?;
+        let mut ctx = SearchContext::new(&index, &rtxn);
+        // panics with `attempt to add with overflow` before <https://github.com/meilisearch/meilisearch/issues/3785>
+        let located_query_terms = located_query_terms_from_tokens(&mut ctx, tokens, None)?;
+        assert!(located_query_terms.is_empty());
+        Ok(())
+    }
+}

milli/src/update/clear_documents.rs

@@ -35,6 +35,7 @@ impl<'t, 'u, 'i> ClearDocuments<'t, 'u, 'i> {
             script_language_docids,
             facet_id_f64_docids,
             facet_id_string_docids,
+            facet_id_string_fst: _,
             facet_id_exists_docids,
             facet_id_is_null_docids,
             facet_id_is_empty_docids,

milli/src/update/delete_documents.rs

@@ -243,6 +243,7 @@ impl<'t, 'u, 'i> DeleteDocuments<'t, 'u, 'i> {
             word_prefix_fid_docids,
             facet_id_f64_docids: _,
             facet_id_string_docids: _,
+            facet_id_string_fst: _,
             field_id_docid_facet_f64s: _,
             field_id_docid_facet_strings: _,
             script_language_docids,

milli/src/update/facet/mod.rs

@@ -78,15 +78,16 @@ pub const FACET_MIN_LEVEL_SIZE: u8 = 5;
 
 use std::fs::File;
 
+use heed::types::DecodeIgnore;
 use log::debug;
 use time::OffsetDateTime;
 
 use self::incremental::FacetsUpdateIncremental;
 use super::FacetsUpdateBulk;
 use crate::facet::FacetType;
-use crate::heed_codec::facet::{FacetGroupKeyCodec, FacetGroupValueCodec};
+use crate::heed_codec::facet::{FacetGroupKey, FacetGroupKeyCodec, FacetGroupValueCodec};
 use crate::heed_codec::ByteSliceRefCodec;
-use crate::{Index, Result};
+use crate::{Index, Result, BEU16};
 
 pub mod bulk;
 pub mod delete;
@@ -157,6 +158,43 @@ impl<'i> FacetsUpdate<'i> {
             );
             incremental_update.execute(wtxn)?;
         }
+
+        // We compute one FST by string facet
+        let mut text_fsts = vec![];
+        let mut current_fst: Option<(u16, fst::SetBuilder<Vec<u8>>)> = None;
+        let database = self.index.facet_id_string_docids.remap_data_type::<DecodeIgnore>();
+        for result in database.iter(wtxn)? {
+            let (facet_group_key, _) = result?;
+            if let FacetGroupKey { field_id, level: 0, left_bound } = facet_group_key {
+                current_fst = match current_fst.take() {
+                    Some((fid, fst_builder)) if fid != field_id => {
+                        let fst = fst_builder.into_set();
+                        text_fsts.push((fid, fst));
+                        Some((field_id, fst::SetBuilder::memory()))
+                    }
+                    Some((field_id, fst_builder)) => Some((field_id, fst_builder)),
+                    None => Some((field_id, fst::SetBuilder::memory())),
+                };
+
+                if let Some((_, fst_builder)) = current_fst.as_mut() {
+                    fst_builder.insert(left_bound)?;
+                }
+            }
+        }
+
+        if let Some((field_id, fst_builder)) = current_fst {
+            let fst = fst_builder.into_set();
+            text_fsts.push((field_id, fst));
+        }
+
+        // We remove all of the previous FSTs that were in this database
+        self.index.facet_id_string_fst.clear(wtxn)?;
+
+        // We write those FSTs in LMDB now
+        for (field_id, fst) in text_fsts {
+            self.index.facet_id_string_fst.put(wtxn, &BEU16::new(field_id), &fst)?;
+        }
+
         Ok(())
     }
 }

milli/src/update/facets.rs

@@ -1 +0,0 @@
-