Merge pull request #676 from MarinPostma/facet-count

Facet count

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## v0.10.2
 
+  - Add support for facet count (#676)
   - Add support for faceted search (#631)
   - Add support for configuring the lmdb map size (#646, #647)
   - Add exposed port for Dockerfile (#654)

Cargo.lock

@@ -522,9 +522,9 @@ dependencies = [
 
 [[package]]
 name = "bstr"
-version = "0.2.12"
+version = "0.2.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2889e6d50f394968c8bf4240dc3f2a7eb4680844d27308f798229ac9d4725f41"
+checksum = "31accafdb70df7871592c058eca3985b71104e15ac32f64706022c58867da931"
 dependencies = [
  "lazy_static",
  "memchr",
@@ -616,9 +616,9 @@ checksum = "5b89647f09b9f4c838cb622799b2843e4e13bff64661dab9a0362bb92985addd"
 
 [[package]]
 name = "clap"
-version = "2.33.0"
+version = "2.33.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5067f5bb2d80ef5d68b4c87db81601f0b75bca627bc2ef76b141d7b846a3c6d9"
+checksum = "bdfa80d47f954d53a35a64987ca1422f495b8d6483c0fe9f7117b36c2a792129"
 dependencies = [
  "ansi_term",
  "atty",
@@ -1008,9 +1008,9 @@ checksum = "3dcaa9ae7725d12cdb85b3ad99a434db70b468c09ded17e012d86b5c1010f7a7"
 
 [[package]]
 name = "futures"
-version = "0.3.4"
+version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5c329ae8753502fb44ae4fc2b622fa2a94652c41e795143765ba0927f92ab780"
+checksum = "1e05b85ec287aac0dc34db7d4a569323df697f9c55b99b15d6b4ef8cde49f613"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -1023,9 +1023,9 @@ dependencies = [
 
 [[package]]
 name = "futures-channel"
-version = "0.3.4"
+version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f0c77d04ce8edd9cb903932b608268b3fffec4163dc053b3b402bf47eac1f1a8"
+checksum = "f366ad74c28cca6ba456d95e6422883cfb4b252a83bed929c83abfdbbf2967d5"
 dependencies = [
  "futures-core",
  "futures-sink",
@@ -1033,15 +1033,15 @@ dependencies = [
 
 [[package]]
 name = "futures-core"
-version = "0.3.4"
+version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f25592f769825e89b92358db00d26f965761e094951ac44d3663ef25b7ac464a"
+checksum = "59f5fff90fd5d971f936ad674802482ba441b6f09ba5e15fd8b39145582ca399"
 
 [[package]]
 name = "futures-executor"
-version = "0.3.4"
+version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f674f3e1bcb15b37284a90cedf55afdba482ab061c407a9c0ebbd0f3109741ba"
+checksum = "10d6bb888be1153d3abeb9006b11b02cf5e9b209fda28693c31ae1e4e012e314"
 dependencies = [
  "futures-core",
  "futures-task",
@@ -1050,15 +1050,15 @@ dependencies = [
 
 [[package]]
 name = "futures-io"
-version = "0.3.4"
+version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a638959aa96152c7a4cddf50fcb1e3fede0583b27157c26e67d6f99904090dc6"
+checksum = "de27142b013a8e869c14957e6d2edeef89e97c289e69d042ee3a49acd8b51789"
 
 [[package]]
 name = "futures-macro"
-version = "0.3.4"
+version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9a5081aa3de1f7542a794a397cde100ed903b0630152d0973479018fd85423a7"
+checksum = "d0b5a30a4328ab5473878237c447333c093297bded83a4983d10f4deea240d39"
 dependencies = [
  "proc-macro-hack",
  "proc-macro2",
@@ -1068,21 +1068,24 @@ dependencies = [
 
 [[package]]
 name = "futures-sink"
-version = "0.3.4"
+version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3466821b4bc114d95b087b850a724c6f83115e929bc88f1fa98a3304a944c8a6"
+checksum = "3f2032893cb734c7a05d85ce0cc8b8c4075278e93b24b66f9de99d6eb0fa8acc"
 
 [[package]]
 name = "futures-task"
-version = "0.3.4"
+version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7b0a34e53cf6cdcd0178aa573aed466b646eb3db769570841fda0c7ede375a27"
+checksum = "bdb66b5f09e22019b1ab0830f7785bcea8e7a42148683f99214f73f8ec21a626"
+dependencies = [
+ "once_cell",
+]
 
 [[package]]
 name = "futures-util"
-version = "0.3.4"
+version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "22766cf25d64306bedf0384da004d05c9974ab104fcc4528f1236181c18004c5"
+checksum = "8764574ff08b701a084482c3c7031349104b07ac897393010494beaa18ce32c6"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -1091,6 +1094,7 @@ dependencies = [
  "futures-sink",
  "futures-task",
  "memchr",
+ "pin-project",
  "pin-utils",
  "proc-macro-hack",
  "proc-macro-nested",
@@ -1398,9 +1402,9 @@ dependencies = [
 
 [[package]]
 name = "intervaltree"
-version = "0.2.5"
+version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8254add2ea664734c9d001f8151cc3d7696b135f7e40e5a2efa814a662cb3a44"
+checksum = "566d5aa3b5cc5c5809cc1a9c9588d917a634248bfc58f7ea14e354e71595a32c"
 dependencies = [
  "smallvec",
 ]
@@ -1660,8 +1664,8 @@ dependencies = [
  "mime",
  "pretty-bytes",
  "rand 0.7.3",
- "sentry",
  "regex",
+ "sentry",
  "serde",
  "serde_json",
  "serde_qs",
@@ -1842,9 +1846,9 @@ dependencies = [
 
 [[package]]
 name = "ntapi"
-version = "0.3.3"
+version = "0.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f26e041cd983acbc087e30fcba770380cfa352d0e392e175b2344ebaf7ea0602"
+checksum = "7a31937dea023539c72ddae0e3571deadc1414b300483fa7aaec176168cfa9d2"
 dependencies = [
  "winapi 0.3.8",
 ]
@@ -1918,9 +1922,9 @@ checksum = "77af24da69f9d9341038eba93a073b1fdaaa1b788221b00a69bce9e762cb32de"
 
 [[package]]
 name = "openssl-sys"
-version = "0.9.55"
+version = "0.9.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7717097d810a0f2e2323f9e5d11e71608355e24828410b55b9d4f18aa5f9a5d8"
+checksum = "f02309a7f127000ed50594f0b50ecc69e7c654e16d41b4e8156d1b3df8e0b52e"
 dependencies = [
  "autocfg",
  "cc",
@@ -2038,18 +2042,18 @@ dependencies = [
 
 [[package]]
 name = "pin-project"
-version = "0.4.13"
+version = "0.4.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "82c3bfbfb5bb42f99498c7234bbd768c220eb0cea6818259d0d18a1aa3d2595d"
+checksum = "81d480cb4e89522ccda96d0eed9af94180b7a5f93fb28f66e1fd7d68431663d1"
 dependencies = [
  "pin-project-internal",
 ]
 
 [[package]]
 name = "pin-project-internal"
-version = "0.4.13"
+version = "0.4.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ccbf6449dcfb18562c015526b085b8df1aa3cdab180af8ec2ebd300a3bd28f63"
+checksum = "a82996f11efccb19b685b14b5df818de31c1edcee3daa256ab5775dd98e72feb"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -2466,9 +2470,9 @@ dependencies = [
 
 [[package]]
 name = "schannel"
-version = "0.1.18"
+version = "0.1.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "039c25b130bd8c1321ee2d7de7fde2659fa9c2744e4bb29711cfc852ea53cd19"
+checksum = "8f05ba609c234e60bee0d547fe94a4c7e9da733d1c962cf6e59efa4cd9c8bc75"
 dependencies = [
  "lazy_static",
  "winapi 0.3.8",
@@ -2498,9 +2502,9 @@ checksum = "cbb21fe0588557792176c89bc7b943027b14f346d03c6be6a199c2860277d93a"
 
 [[package]]
 name = "security-framework"
-version = "0.4.3"
+version = "0.4.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3f331b9025654145cd425b9ded0caf8f5ae0df80d418b326e2dc1c3dc5eb0620"
+checksum = "64808902d7d99f78eaddd2b4e2509713babc3dc3c85ad6f4c447680f3c01e535"
 dependencies = [
  "bitflags",
  "core-foundation",
@@ -2575,18 +2579,18 @@ dependencies = [
 
 [[package]]
 name = "serde"
-version = "1.0.106"
+version = "1.0.110"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "36df6ac6412072f67cf767ebbde4133a5b2e88e76dc6187fa7104cd16f783399"
+checksum = "99e7b308464d16b56eba9964e4972a3eee817760ab60d88c3f86e1fecb08204c"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.106"
+version = "1.0.110"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9e549e3abf4fb8621bd1609f11dfc9f5e50320802273b12f3811a67e6716ea6c"
+checksum = "818fbf6bfa9a42d3bfcaca148547aa00c7b915bec71d1757aa2d44ca68771984"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -2595,9 +2599,9 @@ dependencies = [
 
 [[package]]
 name = "serde_json"
-version = "1.0.52"
+version = "1.0.53"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a7894c8ed05b7a3a279aeb79025fdec1d3158080b75b98a08faf2806bb799edd"
+checksum = "993948e75b189211a9b31a7528f950c6adc21f9720b6438ff80a7fa2f864cea2"
 dependencies = [
  "indexmap",
  "itoa",
@@ -2853,9 +2857,9 @@ dependencies = [
 
 [[package]]
 name = "threadpool"
-version = "1.8.0"
+version = "1.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e8dae184447c15d5a6916d973c642aec485105a13cd238192a6927ae3e077d66"
+checksum = "d050e60b33d41c19108b32cea32164033a9013fe3b46cbd4457559bfbf77afaa"
 dependencies = [
  "num_cpus",
 ]

meilisearch-core/examples/from_file.rs

@@ -371,12 +371,12 @@ fn search_command(command: SearchCommand, database: Database) -> Result<(), Box<
                     });
                 }
 
-                let (documents, _nb_hits) = builder.query(ref_reader, &query, 0..command.number_results)?;
+                let result = builder.query(ref_reader, &query, 0..command.number_results)?;
 
                 let mut retrieve_duration = Duration::default();
 
-                let number_of_documents = documents.len();
+                let number_of_documents = result.documents.len();
-                for mut doc in documents {
+                for mut doc in result.documents {
                     doc.highlights
                         .sort_unstable_by_key(|m| (m.char_index, m.char_length));
 

meilisearch-core/src/bucket_sort.rs

@@ -11,7 +11,7 @@ use std::fmt;
 use compact_arena::{SmallArena, Idx32, mk_arena};
 use log::debug;
 use meilisearch_types::DocIndex;
-use sdset::{Set, SetBuf, exponential_search, SetOperation};
+use sdset::{Set, SetBuf, exponential_search, SetOperation, Counter, duo::OpBuilder};
 use slice_group_by::{GroupBy, GroupByMut};
 
 use crate::error::Error;
@@ -24,11 +24,21 @@ use crate::query_tree::{create_query_tree, traverse_query_tree};
 use crate::query_tree::{Operation, QueryResult, QueryKind, QueryId, PostingsKey};
 use crate::query_tree::Context as QTContext;
 
+#[derive(Debug, Default)]
+pub struct SortResult {
+    pub documents: Vec<Document>,
+    pub nb_hits: usize,
+    pub exhaustive_nb_hit: bool,
+    pub facets: Option<HashMap<String, HashMap<String, usize>>>,
+    pub exhaustive_facet_count: Option<bool>,
+}
+
 pub fn bucket_sort<'c, FI>(
     reader: &heed::RoTxn<MainT>,
     query: &str,
     range: Range<usize>,
     facets_docids: Option<SetBuf<DocumentId>>,
+    facet_count_docids: Option<HashMap<String, HashMap<String, Cow<Set<DocumentId>>>>>,
     filter: Option<FI>,
     criteria: Criteria<'c>,
     searchable_attrs: Option<ReorderedAttrs>,
@@ -38,7 +48,7 @@ pub fn bucket_sort<'c, FI>(
     synonyms_store: store::Synonyms,
     prefix_documents_cache_store: store::PrefixDocumentsCache,
     prefix_postings_lists_cache_store: store::PrefixPostingsListsCache,
-) -> MResult<(Vec<Document>, usize)>
+) -> MResult<SortResult>
 where
     FI: Fn(DocumentId) -> bool,
 {
@@ -52,6 +62,7 @@ where
             query,
             range,
             facets_docids,
+            facet_count_docids,
             filter,
             distinct,
             distinct_size,
@@ -66,9 +77,11 @@ where
         );
     }
 
+    let mut result = SortResult::default();
+
     let words_set = match unsafe { main_store.static_words_fst(reader)? } {
         Some(words) => words,
-        None => return Ok((Vec::new(), 0)),
+        None => return Ok(SortResult::default()),
     };
 
     let stop_words = main_store.stop_words_fst(reader)?.unwrap_or_default();
@@ -107,6 +120,12 @@ where
         docids = Cow::Owned(intersection);
     }
 
+    if let Some(f) = facet_count_docids {
+        // hardcoded value, until approximation optimization
+        result.exhaustive_facet_count = Some(true);
+        result.facets = Some(facet_count(f, &docids));
+    }
+
     let before = Instant::now();
     mk_arena!(arena);
     let mut bare_matches = cleanup_bare_matches(&mut arena, &docids, queries);
@@ -181,7 +200,10 @@ where
 
     debug!("bucket sort took {:.02?}", before_bucket_sort.elapsed());
 
-    Ok((documents, docids.len()))
+    result.documents = documents;
+    result.nb_hits = docids.len();
+
+    Ok(result)
 }
 
 pub fn bucket_sort_with_distinct<'c, FI, FD>(
@@ -189,6 +211,7 @@ pub fn bucket_sort_with_distinct<'c, FI, FD>(
     query: &str,
     range: Range<usize>,
     facets_docids: Option<SetBuf<DocumentId>>,
+    facet_count_docids: Option<HashMap<String, HashMap<String, Cow<Set<DocumentId>>>>>,
     filter: Option<FI>,
     distinct: FD,
     distinct_size: usize,
@@ -200,14 +223,16 @@ pub fn bucket_sort_with_distinct<'c, FI, FD>(
     synonyms_store: store::Synonyms,
     _prefix_documents_cache_store: store::PrefixDocumentsCache,
     prefix_postings_lists_cache_store: store::PrefixPostingsListsCache,
-) -> MResult<(Vec<Document>, usize)>
+) -> MResult<SortResult>
 where
     FI: Fn(DocumentId) -> bool,
     FD: Fn(DocumentId) -> Option<u64>,
 {
+    let mut result = SortResult::default();
+
     let words_set = match unsafe { main_store.static_words_fst(reader)? } {
         Some(words) => words,
-        None => return Ok((Vec::new(), 0)),
+        None => return Ok(SortResult::default()),
     };
 
     let stop_words = main_store.stop_words_fst(reader)?.unwrap_or_default();
@@ -240,12 +265,18 @@ where
     debug!("number of postings {:?}", queries.len());
 
     if let Some(facets_docids) = facets_docids {
-        let intersection = sdset::duo::OpBuilder::new(docids.as_ref(), facets_docids.as_set())
+        let intersection = OpBuilder::new(docids.as_ref(), facets_docids.as_set())
             .intersection()
             .into_set_buf();
         docids = Cow::Owned(intersection);
     }
 
+    if let Some(f) = facet_count_docids {
+        // hardcoded value, until approximation optimization
+        result.exhaustive_facet_count = Some(true);
+        result.facets = Some(facet_count(f, &docids));
+    }
+
     let before = Instant::now();
     mk_arena!(arena);
     let mut bare_matches = cleanup_bare_matches(&mut arena, &docids, queries);
@@ -379,8 +410,10 @@ where
             }
         }
     }
+    result.documents = documents;
+    result.nb_hits = docids.len();
 
-    Ok((documents, docids.len()))
+    Ok(result)
 }
 
 fn cleanup_bare_matches<'tag, 'txn>(
@@ -575,3 +608,22 @@ impl Deref for PostingsListView<'_> {
         }
     }
 }
+
+/// For each entry in facet_docids, calculates the number of documents in the intersection with candidate_docids.
+fn facet_count(
+    facet_docids: HashMap<String, HashMap<String, Cow<Set<DocumentId>>>>,
+    candidate_docids: &Set<DocumentId>,
+) -> HashMap<String, HashMap<String, usize>> {
+    let mut facets_counts = HashMap::with_capacity(facet_docids.len());
+    for (key, doc_map) in facet_docids {
+        let mut count_map = HashMap::with_capacity(doc_map.len());
+        for (value, docids) in doc_map {
+            let mut counter = Counter::new();
+            let op = OpBuilder::new(docids.as_ref(), candidate_docids).intersection();
+            SetOperation::<DocumentId>::extend_collection(op, &mut counter);
+            count_map.insert(value, counter.0);
+        }
+        facets_counts.insert(key, count_map);
+    }
+    facets_counts
+}

meilisearch-core/src/database.rs

@@ -371,6 +371,7 @@ impl Database {
 mod tests {
     use super::*;
 
+    use crate::bucket_sort::SortResult;
     use crate::criterion::{self, CriteriaBuilder};
     use crate::update::{ProcessedUpdateResult, UpdateStatus};
     use crate::settings::Settings;
@@ -675,8 +676,8 @@ mod tests {
 
         // even try to search for a document
         let reader = db.main_read_txn().unwrap();
-        let (results, _nb_hits) = index.query_builder().query(&reader, "21 ", 0..20).unwrap();
+        let SortResult {documents, .. } = index.query_builder().query(&reader, "21 ", 0..20).unwrap();
-        assert_matches!(results.len(), 1);
+        assert_matches!(documents.len(), 1);
 
         reader.abort();
 
@@ -1073,8 +1074,8 @@ mod tests {
 
         let builder = index.query_builder_with_criteria(criteria);
 
-        let (results, _nb_hits) = builder.query(&reader, "Kevin", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "Kevin", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(
             iter.next(),

meilisearch-core/src/query_builder.rs

@@ -1,27 +1,31 @@
 use std::borrow::Cow;
+use std::collections::HashMap;
 use std::ops::{Range, Deref};
 use std::time::Duration;
 
-use crate::database::MainT;
-use crate::bucket_sort::{bucket_sort, bucket_sort_with_distinct};
-use crate::{criterion::Criteria, Document, DocumentId};
-use crate::{reordered_attrs::ReorderedAttrs, store, MResult};
-use crate::facets::FacetFilter;
-
 use either::Either;
 use sdset::SetOperation;
 
-pub struct QueryBuilder<'c, 'f, 'd, 'fa, 'i> {
+use meilisearch_schema::FieldId;
+
+use crate::database::MainT;
+use crate::bucket_sort::{bucket_sort, bucket_sort_with_distinct, SortResult};
+use crate::{criterion::Criteria, DocumentId};
+use crate::{reordered_attrs::ReorderedAttrs, store, MResult};
+use crate::facets::FacetFilter;
+
+pub struct QueryBuilder<'c, 'f, 'd, 'i> {
     criteria: Criteria<'c>,
     searchable_attrs: Option<ReorderedAttrs>,
     filter: Option<Box<dyn Fn(DocumentId) -> bool + 'f>>,
     distinct: Option<(Box<dyn Fn(DocumentId) -> Option<u64> + 'd>, usize)>,
     timeout: Option<Duration>,
     index: &'i store::Index,
-    facets: Option<&'fa FacetFilter>,
+    facet_filter: Option<FacetFilter>,
+    facets: Option<Vec<(FieldId, String)>>,
 }
 
-impl<'c, 'f, 'd, 'fa, 'i> QueryBuilder<'c, 'f, 'd, 'fa, 'i> {
+impl<'c, 'f, 'd, 'i> QueryBuilder<'c, 'f, 'd, 'i> {
     pub fn new(index: &'i store::Index) -> Self {
         QueryBuilder::with_criteria(
             index,
@@ -29,7 +33,13 @@ impl<'c, 'f, 'd, 'fa, 'i> QueryBuilder<'c, 'f, 'd, 'fa, 'i> {
         )
     }
 
-    pub fn set_facets(&mut self, facets: Option<&'fa FacetFilter>) {
+    /// sets facet attributes to filter on
+    pub fn set_facet_filter(&mut self, facets: Option<FacetFilter>) {
+        self.facet_filter = facets;
+    }
+
+    /// sets facet attributes for which to return the count
+    pub fn set_facets(&mut self, facets: Option<Vec<(FieldId, String)>>) {
         self.facets = facets;
     }
 
@@ -44,6 +54,7 @@ impl<'c, 'f, 'd, 'fa, 'i> QueryBuilder<'c, 'f, 'd, 'fa, 'i> {
             distinct: None,
             timeout: None,
             index,
+            facet_filter: None,
             facets: None,
         }
     }
@@ -76,8 +87,8 @@ impl<'c, 'f, 'd, 'fa, 'i> QueryBuilder<'c, 'f, 'd, 'fa, 'i> {
         reader: &heed::RoTxn<MainT>,
         query: &str,
         range: Range<usize>,
-    ) -> MResult<(Vec<Document>, usize)> {
+    ) -> MResult<SortResult> {
-        let facets_docids = match self.facets {
+        let facets_docids = match self.facet_filter {
             Some(facets) => {
                 let mut ands = Vec::with_capacity(facets.len());
                 let mut ors = Vec::new();
@@ -98,7 +109,7 @@ impl<'c, 'f, 'd, 'fa, 'i> QueryBuilder<'c, 'f, 'd, 'fa, 'i> {
                             match self.index.facets.facet_document_ids(reader, &key)? {
                                 Some(docids) => ands.push(docids),
                                 // no candidates for search, early return.
-                                None => return Ok((vec![], 0)),
+                                None => return Ok(SortResult::default()),
                             }
                         }
                     };
@@ -109,12 +120,33 @@ impl<'c, 'f, 'd, 'fa, 'i> QueryBuilder<'c, 'f, 'd, 'fa, 'i> {
             None => None
         };
 
+        // for each field to retrieve the count for, create an HashMap associating the attribute
+        // value to a set of matching documents. The HashMaps are them collected in another
+        // HashMap, associating each HashMap to it's field.
+        let facet_count_docids = match self.facets {
+            Some(field_ids) => {
+                let mut facet_count_map = HashMap::new();
+                for (field_id, field_name) in field_ids {
+                    let mut key_map = HashMap::new();
+                    for pair in self.index.facets.field_document_ids(reader, field_id)? {
+                        let (facet_key, document_ids) = pair?;
+                        let value = facet_key.value();
+                        key_map.insert(value.to_string(), document_ids);
+                    }
+                    facet_count_map.insert(field_name, key_map);
+                }
+                Some(facet_count_map)
+            }
+            None => None,
+        };
+
         match self.distinct {
             Some((distinct, distinct_size)) => bucket_sort_with_distinct(
                 reader,
                 query,
                 range,
                 facets_docids,
+                facet_count_docids,
                 self.filter,
                 distinct,
                 distinct_size,
@@ -132,6 +164,7 @@ impl<'c, 'f, 'd, 'fa, 'i> QueryBuilder<'c, 'f, 'd, 'fa, 'i> {
                 query,
                 range,
                 facets_docids,
+                facet_count_docids,
                 self.filter,
                 self.criteria,
                 self.searchable_attrs,
@@ -159,6 +192,7 @@ mod tests {
     use tempfile::TempDir;
 
     use crate::DocIndex;
+    use crate::Document;
     use crate::automaton::normalize_str;
     use crate::bucket_sort::SimpleMatch;
     use crate::database::{Database,DatabaseOptions};
@@ -349,8 +383,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "iphone from apple", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, "iphone from apple", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -372,8 +406,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "hello", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, "hello", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -383,8 +417,8 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "bonjour", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, "bonjour", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -406,7 +440,7 @@ mod tests {
 
     //     let builder = store.query_builder();
     //     let results = builder.query(&reader, "sal", 0..20).unwrap();
-    //     let mut iter = results.into_iter();
+    //     let mut iter = documents.into_iter();
 
     //     assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
     //         let mut matches = matches.into_iter();
@@ -417,7 +451,7 @@ mod tests {
 
     //     let builder = store.query_builder();
     //     let results = builder.query(&reader, "bonj", 0..20).unwrap();
-    //     let mut iter = results.into_iter();
+    //     let mut iter = documents.into_iter();
 
     //     assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
     //         let mut matches = matches.into_iter();
@@ -428,13 +462,13 @@ mod tests {
 
     //     let builder = store.query_builder();
     //     let results = builder.query(&reader, "sal blabla", 0..20).unwrap();
-    //     let mut iter = results.into_iter();
+    //     let mut iter = documents.into_iter();
 
     //     assert_matches!(iter.next(), None);
 
     //     let builder = store.query_builder();
     //     let results = builder.query(&reader, "bonj blabla", 0..20).unwrap();
-    //     let mut iter = results.into_iter();
+    //     let mut iter = documents.into_iter();
 
     //     assert_matches!(iter.next(), None);
     // }
@@ -450,7 +484,7 @@ mod tests {
 
     //     let builder = store.query_builder();
     //     let results = builder.query(&reader, "salutution", 0..20).unwrap();
-    //     let mut iter = results.into_iter();
+    //     let mut iter = documents.into_iter();
 
     //     assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
     //         let mut matches = matches.into_iter();
@@ -461,7 +495,7 @@ mod tests {
 
     //     let builder = store.query_builder();
     //     let results = builder.query(&reader, "saluttion", 0..20).unwrap();
-    //     let mut iter = results.into_iter();
+    //     let mut iter = documents.into_iter();
 
     //     assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
     //         let mut matches = matches.into_iter();
@@ -487,8 +521,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "hello", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, "hello", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -508,8 +542,8 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "bonjour", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, "bonjour", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -529,8 +563,8 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "salut", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, "salut", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -575,8 +609,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "NY subway", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, "NY subway", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
             let mut iter = matches.into_iter();
@@ -597,8 +631,8 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "NYC subway", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, "NYC subway", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
             let mut iter = matches.into_iter();
@@ -639,8 +673,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "NY", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "NY", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(2), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -663,8 +697,8 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "new york", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "new york", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -697,8 +731,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "NY subway", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "NY subway", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -714,8 +748,8 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "new york subway", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "new york subway", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -762,8 +796,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "NY subway", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "NY subway", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
             let mut iter = matches.into_iter();
@@ -784,8 +818,8 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "NYC subway", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "NYC subway", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
             let mut iter = matches.into_iter();
@@ -837,8 +871,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "NY subway broken", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "NY subway broken", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut iter = matches.into_iter();
@@ -853,8 +887,8 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "NYC subway", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "NYC subway", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
             let mut iter = matches.into_iter();
@@ -909,10 +943,10 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder
+        let SortResult {documents, .. } = builder
             .query(&reader, "new york underground train broken", 0..20)
             .unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(2), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -939,10 +973,10 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder
+        let SortResult {documents, .. } = builder
             .query(&reader, "new york city underground train broken", 0..20)
             .unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(2), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -983,8 +1017,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "new york big ", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "new york big ", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -1017,8 +1051,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "NY subway ", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "NY subway ", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -1067,10 +1101,10 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder
+        let SortResult {documents, .. } = builder
             .query(&reader, "new york city long subway cool ", 0..20)
             .unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut matches = matches.into_iter();
@@ -1100,8 +1134,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "telephone", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "telephone", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut iter = matches.into_iter();
@@ -1117,8 +1151,8 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "téléphone", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "téléphone", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut iter = matches.into_iter();
@@ -1134,8 +1168,8 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "télephone", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "télephone", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
             let mut iter = matches.into_iter();
@@ -1161,8 +1195,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "i phone case", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "i phone case", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut iter = matches.into_iter();
@@ -1190,8 +1224,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "searchengine", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "searchengine", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut iter = matches.into_iter();
@@ -1230,8 +1264,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "searchengine", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "searchengine", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut iter = matches.into_iter();
@@ -1262,8 +1296,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let (results, _nb_hits) = builder.query(&reader, "searchengine", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, "searchengine", 0..20).unwrap();
-        let mut iter = results.into_iter();
+        let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
             let mut iter = matches.into_iter();

meilisearch-core/src/store/facets.rs

@@ -1,10 +1,11 @@
 use std::borrow::Cow;
 use std::collections::HashMap;
 
-use heed::{RwTxn, RoTxn, Result as ZResult};
+use heed::{RwTxn, RoTxn, Result as ZResult, RoRange};
 use sdset::{SetBuf, Set, SetOperation};
 
 use meilisearch_types::DocumentId;
+use meilisearch_schema::FieldId;
 
 use crate::database::MainT;
 use crate::facets::FacetKey;
@@ -22,6 +23,10 @@ impl Facets {
         self.facets.put(writer, &facet_key, doc_ids)
     }
 
+    pub fn field_document_ids<'txn>(&self, reader: &'txn RoTxn<MainT>, field_id: FieldId) -> ZResult<RoRange<'txn, FacetKey, CowSet<DocumentId>>> {
+        self.facets.prefix_iter(reader, &FacetKey::new(field_id, String::new()))
+    }
+
     pub fn facet_document_ids<'txn>(&self, reader: &'txn RoTxn<MainT>, facet_key: &FacetKey) -> ZResult<Option<Cow<'txn, Set<DocumentId>>>> {
         self.facets.get(reader, &facet_key)
     }

meilisearch-core/src/store/mod.rs

@@ -363,10 +363,10 @@ impl Index {
         QueryBuilder::new(self)
     }
 
-    pub fn query_builder_with_criteria<'c, 'f, 'd, 'fa, 'i>(
+    pub fn query_builder_with_criteria<'c, 'f, 'd, 'i>(
         &'i self,
         criteria: Criteria<'c>,
-    ) -> QueryBuilder<'c, 'f, 'd, 'fa, 'i> {
+    ) -> QueryBuilder<'c, 'f, 'd, 'i> {
         QueryBuilder::with_criteria(self, criteria)
     }
 }

meilisearch-http/src/error.rs

@@ -27,6 +27,40 @@ pub enum ResponseError {
     PayloadTooLarge,
     UnsupportedMediaType,
     FacetExpression(String),
+    FacetCount(String),
+}
+
+pub enum FacetCountError {
+    AttributeNotSet(String),
+    SyntaxError(String),
+    UnexpectedToken { found: String, expected: &'static [&'static str] },
+    NoFacetSet,
+}
+
+impl FacetCountError {
+    pub fn unexpected_token(found: impl ToString, expected: &'static [&'static str]) -> FacetCountError {
+        let found = found.to_string();
+        FacetCountError::UnexpectedToken { expected, found }
+    }
+}
+
+impl From<serde_json::error::Error> for FacetCountError {
+    fn from(other: serde_json::error::Error) -> FacetCountError {
+        FacetCountError::SyntaxError(other.to_string())
+    }
+}
+
+impl fmt::Display for FacetCountError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        use FacetCountError::*;
+
+        match self {
+            AttributeNotSet(attr) => write!(f, "attribute {} is not set as facet", attr),
+            SyntaxError(msg) => write!(f, "syntax error: {}", msg),
+            UnexpectedToken { expected, found } => write!(f, "unexpected {} found, expected {:?}", found, expected),
+            NoFacetSet => write!(f, "can't perform facet count, as no facet is set"),
+        }
+    }
 }
 
 impl ResponseError {
@@ -112,7 +146,8 @@ impl fmt::Display for ResponseError {
             Self::SearchDocuments(err) => write!(f, "impossible to search documents; {}", err),
             Self::FacetExpression(e) => write!(f, "error parsing facet filter expression: {}", e),
             Self::PayloadTooLarge => f.write_str("Payload to large"),
-            Self::UnsupportedMediaType => f.write_str("Unsupported media type")
+            Self::UnsupportedMediaType => f.write_str("Unsupported media type"),
+            Self::FacetCount(e) => write!(f, "error with facet count: {}", e),
         }
     }
 }
@@ -134,6 +169,7 @@ impl aweb::error::ResponseError for ResponseError {
             | Self::RetrieveDocument(_, _)
             | Self::FacetExpression(_)
             | Self::SearchDocuments(_)
+            | Self::FacetCount(_)
             | Self::FilterParsing(_) => StatusCode::BAD_REQUEST,
             Self::DocumentNotFound(_)
             | Self::IndexNotFound(_)
@@ -198,18 +234,23 @@ impl From<actix_http::Error> for ResponseError {
     }
 }
 
-impl From<JsonPayloadError> for ResponseError {
+impl From<FacetCountError> for ResponseError {
-    fn from(err: JsonPayloadError) -> ResponseError {
+    fn from(other: FacetCountError) -> ResponseError {
-        match err {
+        ResponseError::FacetCount(other.to_string())
-                JsonPayloadError::Deserialize(err) => ResponseError::BadRequest(format!("Invalid JSON: {}", err)),
-                JsonPayloadError::Overflow => ResponseError::PayloadTooLarge,
-                JsonPayloadError::ContentType => ResponseError::UnsupportedMediaType,
-                JsonPayloadError::Payload(err) => ResponseError::BadRequest(format!("Problem while decoding the request: {}", err)),
-            }
     }
 }
 
+impl From<JsonPayloadError> for ResponseError {
+    fn from(err: JsonPayloadError) -> ResponseError {
+        match err {
+            JsonPayloadError::Deserialize(err) => ResponseError::BadRequest(format!("Invalid JSON: {}", err)),
+            JsonPayloadError::Overflow => ResponseError::PayloadTooLarge,
+            JsonPayloadError::ContentType => ResponseError::UnsupportedMediaType,
+            JsonPayloadError::Payload(err) => ResponseError::BadRequest(format!("Problem while decoding the request: {}", err)),
+        }
+    }
+}
 
 pub fn json_error_handler(err: JsonPayloadError) -> ResponseError {
-	err.into()
+    err.into()
 }

meilisearch-http/src/helpers/meilisearch.rs

@@ -36,6 +36,7 @@ impl IndexSearchExt for Index {
             filters: None,
             matches: false,
             facet_filters: None,
+            facets: None,
         }
     }
 }
@@ -51,6 +52,7 @@ pub struct SearchBuilder<'a> {
     filters: Option<String>,
     matches: bool,
     facet_filters: Option<FacetFilter>,
+    facets: Option<Vec<(FieldId, String)>>
 }
 
 impl<'a> SearchBuilder<'a> {
@@ -100,7 +102,12 @@ impl<'a> SearchBuilder<'a> {
         self
     }
 
-    pub fn search(&self, reader: &heed::RoTxn<MainT>) -> Result<SearchResult, ResponseError> {
+    pub fn add_facets(&mut self, facets: Vec<(FieldId, String)>) -> &SearchBuilder {
+        self.facets = Some(facets);
+        self
+    }
+
+    pub fn search(self, reader: &heed::RoTxn<MainT>) -> Result<SearchResult, ResponseError> {
         let schema = self
             .index
             .main
@@ -117,8 +124,8 @@ impl<'a> SearchBuilder<'a> {
 
         if let Some(filter_expression) = &self.filters {
             let filter = Filter::parse(filter_expression, &schema)?;
+            let index = &self.index;
             query_builder.with_filter(move |id| {
-                let index = &self.index;
                 let reader = &reader;
                 let filter = &filter;
                 match filter.test(reader, index, id) {
@@ -133,8 +140,9 @@ impl<'a> SearchBuilder<'a> {
 
         if let Some(field) = self.index.main.distinct_attribute(reader)? {
             if let Some(field_id) = schema.id(&field) {
+                let index = &self.index;
                 query_builder.with_distinct(1, move |id| {
-                    match self.index.document_attribute_bytes(reader, id, field_id) {
+                    match index.document_attribute_bytes(reader, id, field_id) {
                         Ok(Some(bytes)) => {
                             let mut s = SipHasher::new();
                             bytes.hash(&mut s);
@@ -146,11 +154,12 @@ impl<'a> SearchBuilder<'a> {
             }
         }
 
-        query_builder.set_facets(self.facet_filters.as_ref());
+        query_builder.set_facet_filter(self.facet_filters);
+        query_builder.set_facets(self.facets);
 
         let start = Instant::now();
         let result = query_builder.query(reader, &self.query, self.offset..(self.offset + self.limit));
-        let (docs, nb_hits) = result.map_err(ResponseError::search_documents)?;
+        let search_result = result.map_err(ResponseError::search_documents)?;
         let time_ms = start.elapsed().as_millis() as usize;
 
         let mut all_attributes: HashSet<&str> = HashSet::new();
@@ -181,7 +190,7 @@ impl<'a> SearchBuilder<'a> {
         }
 
         let mut hits = Vec::with_capacity(self.limit);
-        for doc in docs {
+        for doc in search_result.documents {
             let mut document: IndexMap<String, Value> = self
                 .index
                 .document(reader, Some(&all_attributes), doc.id)
@@ -235,10 +244,11 @@ impl<'a> SearchBuilder<'a> {
             hits,
             offset: self.offset,
             limit: self.limit,
-            nb_hits,
+            nb_hits: search_result.nb_hits,
-            exhaustive_nb_hits: false,
+            exhaustive_nb_hits: search_result.exhaustive_nb_hit,
             processing_time_ms: time_ms,
             query: self.query.to_string(),
+            facets: search_result.facets,
         };
 
         Ok(results)
@@ -323,6 +333,7 @@ pub struct SearchResult {
     pub exhaustive_nb_hits: bool,
     pub processing_time_ms: usize,
     pub query: String,
+    pub facets: Option<HashMap<String, HashMap<String, usize>>>,
 }
 
 /// returns the start index and the length on the crop.

meilisearch-http/src/routes/search.rs

@@ -5,14 +5,16 @@ use actix_web::web;
 use actix_web::HttpResponse;
 use actix_web_macros::get;
 use serde::Deserialize;
+use serde_json::Value;
 
-use crate::error::ResponseError;
+use crate::error::{ResponseError, FacetCountError};
 use crate::helpers::meilisearch::IndexSearchExt;
 use crate::helpers::Authentication;
 use crate::routes::IndexParam;
 use crate::Data;
 
 use meilisearch_core::facets::FacetFilter;
+use meilisearch_schema::{Schema, FieldId};
 
 pub fn services(cfg: &mut web::ServiceConfig) {
     cfg.service(search_with_url_query);
@@ -31,6 +33,7 @@ struct SearchQuery {
     filters: Option<String>,
     matches: Option<bool>,
     facet_filters: Option<String>,
+    facets: Option<String>,
 }
 
 #[get("/indexes/{index_uid}/search", wrap = "Authentication::Public")]
@@ -91,6 +94,16 @@ async fn search_with_url_query(
         }
     }
 
+    if let Some(facets) = &params.facets {
+        match index.main.attributes_for_faceting(&reader)? {
+            Some(ref attrs) => {
+                let field_ids = prepare_facet_list(&facets, &schema, attrs)?;
+                search_builder.add_facets(field_ids);
+            },
+            None => return Err(FacetCountError::NoFacetSet.into())
+        }
+    }
+
     if let Some(attributes_to_crop) = &params.attributes_to_crop {
         let default_length = params.crop_length.unwrap_or(200);
         let mut final_attributes: HashMap<String, usize> = HashMap::new();
@@ -150,3 +163,40 @@ async fn search_with_url_query(
 
     Ok(HttpResponse::Ok().json(search_builder.search(&reader)?))
 }
+
+/// Parses the incoming string into an array of attributes for which to return a count. It returns
+/// a Vec of attribute names ascociated with their id.
+///
+/// An error is returned if the array is malformed, or if it contains attributes that are
+/// unexisting, or not set as facets.
+fn prepare_facet_list(facets: &str, schema: &Schema, facet_attrs: &[FieldId]) -> Result<Vec<(FieldId, String)>, FacetCountError> {
+    let json_array = serde_json::from_str(facets)?;
+    match json_array {
+        Value::Array(vals) => {
+            let wildcard = Value::String("*".to_string());
+            if vals.iter().any(|f| f == &wildcard) {
+                let attrs = facet_attrs
+                    .iter()
+                    .filter_map(|&id| schema.name(id).map(|n| (id, n.to_string())))
+                    .collect();
+                return Ok(attrs);
+            }
+            let mut field_ids = Vec::with_capacity(facet_attrs.len());
+            for facet in vals {
+                match facet {
+                    Value::String(facet) => {
+                        if let Some(id) = schema.id(&facet) {
+                            if !facet_attrs.contains(&id) {
+                                return Err(FacetCountError::AttributeNotSet(facet));
+                            }
+                            field_ids.push((id, facet));
+                        }
+                    }
+                    bad_val => return Err(FacetCountError::unexpected_token(bad_val, &["String"])),
+                }
+            }
+            Ok(field_ids)
+        }
+        bad_val => return Err(FacetCountError::unexpected_token(bad_val, &["[String]"]))
+    }
+}

meilisearch-http/tests/search.rs

@@ -1292,3 +1292,54 @@ async fn test_faceted_search_invalid() {
     let (_response, status_code) = server.search(query).await;
     assert_ne!(status_code, 202);
 }
+
+#[actix_rt::test]
+async fn test_facet_count() {
+    let mut server = common::Server::test_server().await;
+
+    // test no facets set, search on color
+    let query = "q=a&facets=%5B%22color%22%5D";
+    let (_response, status_code) = server.search(query).await;
+    assert_eq!(status_code, 400);
+
+    let body = json!({
+        "attributesForFaceting": ["color", "tags"]
+    });
+    server.update_all_settings(body).await;
+    // same as before, but now facets are set:
+    let (response, _status_code) = server.search(query).await;
+    assert_eq!(response.get("facets").unwrap().as_object().unwrap().values().count(), 1);
+    // searching on color and tags
+    let query = "q=a&facets=%5B%22color%22,%20%22tags%22%5D";
+    let (response, _status_code) = server.search(query).await;
+    let facets = response.get("facets").unwrap().as_object().unwrap();
+    eprintln!("response: {:#?}", response);
+    assert_eq!(facets.values().count(), 2);
+    assert_ne!(!facets.get("color").unwrap().as_object().unwrap().values().count(), 0);
+    assert_ne!(!facets.get("tags").unwrap().as_object().unwrap().values().count(), 0);
+    // wildcard
+    let query = "q=a&facets=%5B%22*%22%5D";
+    let (response, _status_code) = server.search(query).await;
+    assert_eq!(response.get("facets").unwrap().as_object().unwrap().values().count(), 2);
+    // wildcard with other attributes:
+    let query = "q=a&facets=%5B%22color%22,%20%22*%22%5D";
+    let (response, _status_code) = server.search(query).await;
+    assert_eq!(response.get("facets").unwrap().as_object().unwrap().values().count(), 2);
+    // empty facet list
+    let query = "q=a&facets=%5B%5D";
+    let (response, _status_code) = server.search(query).await;
+    assert_eq!(response.get("facets").unwrap().as_object().unwrap().values().count(), 0);
+
+    // attr not set as facet passed:
+    let query = "q=a&facets=%5B%22gender%22%5D";
+    let (_response, status_code) = server.search(query).await;
+    assert_eq!(status_code, 400);
+    // string instead of array:
+    let query = "q=a&facets=%22gender%22";
+    let (_response, status_code) = server.search(query).await;
+    assert_eq!(status_code, 400);
+    // invalid value in array:
+    let query = "q=a&facets=%5B%22color%22,%20true%5D";
+    let (_response, status_code) = server.search(query).await;
+    assert_eq!(status_code, 400);
+}