Merge #4140

4140: Fix bug where search with distinct attribute has wrong totalHits and totalPages r=dureuill a=vivek-26

# Pull Request

## Related issue
Fixes #4130

## What does this PR do?
This PR - 
- Fixes the bug where search with distinct attribute and pagination (no ranking) returns incorrect values for `totalHits` and `totalPages`.
- Add/update unit and integration tests.

## PR checklist
Please check if your PR fulfills the following requirements:
- [x] Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
- [x] Have you read the contributing guidelines?
- [x] Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!


Co-authored-by: Vivek Kumar <vivek.26@outlook.com>
Co-authored-by: Louis Dureuil <louis.dureuil@gmail.com>

Cargo.lock

@@ -468,7 +468,7 @@ checksum = "8c3c1a368f70d6cf7302d78f8f7093da241fb8e8807c05cc9e51a125895a6d5b"
 
 [[package]]
 name = "benchmarks"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "anyhow",
  "bytes",
@@ -1206,7 +1206,7 @@ dependencies = [
 
 [[package]]
 name = "dump"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "anyhow",
  "big_s",
@@ -1417,7 +1417,7 @@ dependencies = [
 
 [[package]]
 name = "file-store"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "faux",
  "tempfile",
@@ -1439,7 +1439,7 @@ dependencies = [
 
 [[package]]
 name = "filter-parser"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "insta",
  "nom",
@@ -1459,7 +1459,7 @@ dependencies = [
 
 [[package]]
 name = "flatten-serde-json"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "criterion",
  "serde_json",
@@ -1577,7 +1577,7 @@ dependencies = [
 
 [[package]]
 name = "fuzzers"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "arbitrary",
  "clap",
@@ -1891,7 +1891,7 @@ dependencies = [
 
 [[package]]
 name = "index-scheduler"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "anyhow",
  "big_s",
@@ -2088,7 +2088,7 @@ dependencies = [
 
 [[package]]
 name = "json-depth-checker"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "criterion",
  "serde_json",
@@ -2500,7 +2500,7 @@ checksum = "490cc448043f947bae3cbee9c203358d62dbee0db12107a74be5c30ccfd09771"
 
 [[package]]
 name = "meili-snap"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "insta",
  "md5",
@@ -2509,7 +2509,7 @@ dependencies = [
 
 [[package]]
 name = "meilisearch"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "actix-cors",
  "actix-http",
@@ -2600,7 +2600,7 @@ dependencies = [
 
 [[package]]
 name = "meilisearch-auth"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "base64 0.21.2",
  "enum-iterator",
@@ -2619,7 +2619,7 @@ dependencies = [
 
 [[package]]
 name = "meilisearch-types"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "actix-web",
  "anyhow",
@@ -2673,7 +2673,7 @@ dependencies = [
 
 [[package]]
 name = "milli"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "big_s",
  "bimap",
@@ -2995,7 +2995,7 @@ checksum = "9b2a4787296e9989611394c33f193f676704af1686e70b8f8033ab5ba9a35a94"
 
 [[package]]
 name = "permissive-json-pointer"
-version = "1.4.0"
+version = "1.4.2"
 dependencies = [
  "big_s",
  "serde_json",

Cargo.toml

@@ -18,7 +18,7 @@ members = [
 ]
 
 [workspace.package]
-version = "1.4.0"
+version = "1.4.2"
 authors = ["Quentin de Quelen <quentin@dequelen.me>", "Clément Renault <clement@meilisearch.com>"]
 description = "Meilisearch HTTP server"
 homepage = "https://meilisearch.com"

meilisearch/tests/search/distinct.rs

@@ -0,0 +1,241 @@
+use meili_snap::snapshot;
+use once_cell::sync::Lazy;
+use serde_json::{json, Value};
+
+use crate::common::Server;
+
+pub(self) static DOCUMENTS: Lazy<Value> = Lazy::new(|| {
+    json!([
+      {
+        "id": 1,
+        "description": "Leather Jacket",
+        "brand": "Lee Jeans",
+        "product_id": "123456",
+        "color": "Brown"
+      },
+      {
+        "id": 2,
+        "description": "Leather Jacket",
+        "brand": "Lee Jeans",
+        "product_id": "123456",
+        "color": "Black"
+      },
+      {
+        "id": 3,
+        "description": "Leather Jacket",
+        "brand": "Lee Jeans",
+        "product_id": "123456",
+        "color": "Blue"
+      },
+      {
+        "id": 4,
+        "description": "T-Shirt",
+        "brand": "Nike",
+        "product_id": "789012",
+        "color": "Red"
+      },
+      {
+        "id": 5,
+        "description": "T-Shirt",
+        "brand": "Nike",
+        "product_id": "789012",
+        "color": "Blue"
+      },
+      {
+        "id": 6,
+        "description": "Running Shoes",
+        "brand": "Adidas",
+        "product_id": "456789",
+        "color": "Black"
+      },
+      {
+        "id": 7,
+        "description": "Running Shoes",
+        "brand": "Adidas",
+        "product_id": "456789",
+        "color": "White"
+      },
+      {
+        "id": 8,
+        "description": "Hoodie",
+        "brand": "Puma",
+        "product_id": "987654",
+        "color": "Gray"
+      },
+      {
+        "id": 9,
+        "description": "Sweater",
+        "brand": "Gap",
+        "product_id": "234567",
+        "color": "Green"
+      },
+      {
+        "id": 10,
+        "description": "Sweater",
+        "brand": "Gap",
+        "product_id": "234567",
+        "color": "Red"
+      },
+      {
+        "id": 11,
+        "description": "Sweater",
+        "brand": "Gap",
+        "product_id": "234567",
+        "color": "Blue"
+      },
+      {
+        "id": 12,
+        "description": "Jeans",
+        "brand": "Levi's",
+        "product_id": "345678",
+        "color": "Indigo"
+      },
+      {
+        "id": 13,
+        "description": "Jeans",
+        "brand": "Levi's",
+        "product_id": "345678",
+        "color": "Black"
+      },
+      {
+        "id": 14,
+        "description": "Jeans",
+        "brand": "Levi's",
+        "product_id": "345678",
+        "color": "Stone Wash"
+      }
+    ])
+});
+
+pub(self) static DOCUMENT_PRIMARY_KEY: &str = "id";
+pub(self) static DOCUMENT_DISTINCT_KEY: &str = "product_id";
+
+/// testing: https://github.com/meilisearch/meilisearch/issues/4078
+#[actix_rt::test]
+async fn distinct_search_with_offset_no_ranking() {
+    let server = Server::new().await;
+    let index = server.index("test");
+
+    let documents = DOCUMENTS.clone();
+    index.add_documents(documents, Some(DOCUMENT_PRIMARY_KEY)).await;
+    index.update_distinct_attribute(json!(DOCUMENT_DISTINCT_KEY)).await;
+    index.wait_task(1).await;
+
+    fn get_hits(response: &Value) -> Vec<&str> {
+        let hits_array = response["hits"].as_array().unwrap();
+        hits_array.iter().map(|h| h[DOCUMENT_DISTINCT_KEY].as_str().unwrap()).collect::<Vec<_>>()
+    }
+
+    let (response, code) = index.search_post(json!({"offset": 0, "limit": 2})).await;
+    let hits = get_hits(&response);
+    snapshot!(code, @"200 OK");
+    snapshot!(hits.len(), @"2");
+    snapshot!(format!("{:?}", hits), @r#"["123456", "789012"]"#);
+    snapshot!(response["estimatedTotalHits"] , @"11");
+
+    let (response, code) = index.search_post(json!({"offset": 2, "limit": 2})).await;
+    let hits = get_hits(&response);
+    snapshot!(code, @"200 OK");
+    snapshot!(hits.len(), @"2");
+    snapshot!(format!("{:?}", hits), @r#"["456789", "987654"]"#);
+    snapshot!(response["estimatedTotalHits"], @"10");
+
+    let (response, code) = index.search_post(json!({"offset": 4, "limit": 2})).await;
+    let hits = get_hits(&response);
+    snapshot!(code, @"200 OK");
+    snapshot!(hits.len(), @"2");
+    snapshot!(format!("{:?}", hits), @r#"["234567", "345678"]"#);
+    snapshot!(response["estimatedTotalHits"], @"6");
+
+    let (response, code) = index.search_post(json!({"offset": 5, "limit": 2})).await;
+    let hits = get_hits(&response);
+    snapshot!(code, @"200 OK");
+    snapshot!(hits.len(), @"1");
+    snapshot!(format!("{:?}", hits), @r#"["345678"]"#);
+    snapshot!(response["estimatedTotalHits"], @"6");
+
+    let (response, code) = index.search_post(json!({"offset": 6, "limit": 2})).await;
+    let hits = get_hits(&response);
+    snapshot!(code, @"200 OK");
+    snapshot!(hits.len(), @"0");
+    snapshot!(format!("{:?}", hits), @r#"[]"#);
+    snapshot!(response["estimatedTotalHits"], @"6");
+
+    let (response, code) = index.search_post(json!({"offset": 7, "limit": 2})).await;
+    let hits = get_hits(&response);
+    snapshot!(code, @"200 OK");
+    snapshot!(hits.len(), @"0");
+    snapshot!(format!("{:?}", hits), @r#"[]"#);
+    snapshot!(response["estimatedTotalHits"], @"6");
+}
+
+/// testing: https://github.com/meilisearch/meilisearch/issues/4130
+#[actix_rt::test]
+async fn distinct_search_with_pagination_no_ranking() {
+    let server = Server::new().await;
+    let index = server.index("test");
+
+    let documents = DOCUMENTS.clone();
+    index.add_documents(documents, Some(DOCUMENT_PRIMARY_KEY)).await;
+    index.update_distinct_attribute(json!(DOCUMENT_DISTINCT_KEY)).await;
+    index.wait_task(1).await;
+
+    fn get_hits(response: &Value) -> Vec<&str> {
+        let hits_array = response["hits"].as_array().unwrap();
+        hits_array.iter().map(|h| h[DOCUMENT_DISTINCT_KEY].as_str().unwrap()).collect::<Vec<_>>()
+    }
+
+    let (response, code) = index.search_post(json!({"page": 0, "hitsPerPage": 2})).await;
+    let hits = get_hits(&response);
+    snapshot!(code, @"200 OK");
+    snapshot!(hits.len(), @"0");
+    snapshot!(format!("{:?}", hits), @r#"[]"#);
+    snapshot!(response["page"], @"0");
+    snapshot!(response["totalPages"], @"3");
+    snapshot!(response["totalHits"], @"6");
+
+    let (response, code) = index.search_post(json!({"page": 1, "hitsPerPage": 2})).await;
+    let hits = get_hits(&response);
+    snapshot!(code, @"200 OK");
+    snapshot!(hits.len(), @"2");
+    snapshot!(format!("{:?}", hits), @r#"["123456", "789012"]"#);
+    snapshot!(response["page"], @"1");
+    snapshot!(response["totalPages"], @"3");
+    snapshot!(response["totalHits"], @"6");
+
+    let (response, code) = index.search_post(json!({"page": 2, "hitsPerPage": 2})).await;
+    let hits = get_hits(&response);
+    snapshot!(code, @"200 OK");
+    snapshot!(hits.len(), @"2");
+    snapshot!(format!("{:?}", hits), @r#"["456789", "987654"]"#);
+    snapshot!(response["page"], @"2");
+    snapshot!(response["totalPages"], @"3");
+    snapshot!(response["totalHits"], @"6");
+
+    let (response, code) = index.search_post(json!({"page": 3, "hitsPerPage": 2})).await;
+    let hits = get_hits(&response);
+    snapshot!(code, @"200 OK");
+    snapshot!(hits.len(), @"2");
+    snapshot!(format!("{:?}", hits), @r#"["234567", "345678"]"#);
+    snapshot!(response["page"], @"3");
+    snapshot!(response["totalPages"], @"3");
+    snapshot!(response["totalHits"], @"6");
+
+    let (response, code) = index.search_post(json!({"page": 4, "hitsPerPage": 2})).await;
+    let hits = get_hits(&response);
+    snapshot!(code, @"200 OK");
+    snapshot!(hits.len(), @"0");
+    snapshot!(format!("{:?}", hits), @r#"[]"#);
+    snapshot!(response["page"], @"4");
+    snapshot!(response["totalPages"], @"3");
+    snapshot!(response["totalHits"], @"6");
+
+    let (response, code) = index.search_post(json!({"page": 2, "hitsPerPage": 3})).await;
+    let hits = get_hits(&response);
+    snapshot!(code, @"200 OK");
+    snapshot!(hits.len(), @"3");
+    snapshot!(format!("{:?}", hits), @r#"["987654", "234567", "345678"]"#);
+    snapshot!(response["page"], @"2");
+    snapshot!(response["totalPages"], @"2");
+    snapshot!(response["totalHits"], @"6");
+}

meilisearch/tests/search/mod.rs

@@ -1,6 +1,7 @@
 // This modules contains all the test concerning search. Each particular feature of the search
 // should be tested in its own module to isolate tests and keep the tests readable.
 
+mod distinct;
 mod errors;
 mod facet_search;
 mod formatted;

milli/src/documents/enriched.rs

@@ -1,4 +1,5 @@
 use std::fs::File;
+use std::io::BufReader;
 use std::{io, str};
 
 use obkv::KvReader;
@@ -19,14 +20,14 @@ use crate::FieldId;
 pub struct EnrichedDocumentsBatchReader<R> {
     documents: DocumentsBatchReader<R>,
     primary_key: String,
-    external_ids: grenad::ReaderCursor<File>,
+    external_ids: grenad::ReaderCursor<BufReader<File>>,
 }
 
 impl<R: io::Read + io::Seek> EnrichedDocumentsBatchReader<R> {
     pub fn new(
         documents: DocumentsBatchReader<R>,
         primary_key: String,
-        external_ids: grenad::Reader<File>,
+        external_ids: grenad::Reader<BufReader<File>>,
     ) -> Result<Self, Error> {
         if documents.documents_count() as u64 == external_ids.len() {
             Ok(EnrichedDocumentsBatchReader {
@@ -75,7 +76,7 @@ pub struct EnrichedDocument<'a> {
 pub struct EnrichedDocumentsBatchCursor<R> {
     documents: DocumentsBatchCursor<R>,
     primary_key: String,
-    external_ids: grenad::ReaderCursor<File>,
+    external_ids: grenad::ReaderCursor<BufReader<File>>,
 }
 
 impl<R> EnrichedDocumentsBatchCursor<R> {

milli/src/search/new/bucket_sort.rs

@@ -53,11 +53,22 @@ pub fn bucket_sort<'ctx, Q: RankingRuleQueryTrait>(
                 if excluded.contains(docid) {
                     continue;
                 }
+
                 distinct_single_docid(ctx.index, ctx.txn, distinct_fid, docid, &mut excluded)?;
                 results.push(docid);
             }
+
             let mut all_candidates = universe - excluded;
             all_candidates.extend(results.iter().copied());
+            // drain the results of the skipped elements
+            // this **must** be done **after** writing the entire results in `all_candidates` to ensure
+            // e.g. estimatedTotalHits is correct.
+            if results.len() >= from {
+                results.drain(..from);
+            } else {
+                results.clear();
+            }
+
             return Ok(BucketSortOutput {
                 scores: vec![Default::default(); results.len()],
                 docids: results,

milli/src/update/facet/bulk.rs

@@ -1,5 +1,6 @@
 use std::borrow::Cow;
 use std::fs::File;
+use std::io::BufReader;
 
 use grenad::CompressionType;
 use heed::types::ByteSlice;
@@ -30,7 +31,7 @@ pub struct FacetsUpdateBulk<'i> {
     facet_type: FacetType,
     field_ids: Vec<FieldId>,
     // None if level 0 does not need to be updated
-    new_data: Option<grenad::Reader<File>>,
+    new_data: Option<grenad::Reader<BufReader<File>>>,
 }
 
 impl<'i> FacetsUpdateBulk<'i> {
@@ -38,7 +39,7 @@ impl<'i> FacetsUpdateBulk<'i> {
         index: &'i Index,
         field_ids: Vec<FieldId>,
         facet_type: FacetType,
-        new_data: grenad::Reader<File>,
+        new_data: grenad::Reader<BufReader<File>>,
         group_size: u8,
         min_level_size: u8,
     ) -> FacetsUpdateBulk<'i> {
@@ -187,7 +188,7 @@ impl<R: std::io::Read + std::io::Seek> FacetsUpdateBulkInner<R> {
         &self,
         field_id: FieldId,
         txn: &RoTxn,
-    ) -> Result<(Vec<grenad::Reader<File>>, RoaringBitmap)> {
+    ) -> Result<(Vec<grenad::Reader<BufReader<File>>>, RoaringBitmap)> {
         let mut all_docids = RoaringBitmap::new();
         let subwriters = self.compute_higher_levels(txn, field_id, 32, &mut |bitmaps, _| {
             for bitmap in bitmaps {
@@ -259,7 +260,7 @@ impl<R: std::io::Read + std::io::Seek> FacetsUpdateBulkInner<R> {
         field_id: u16,
         level: u8,
         handle_group: &mut dyn FnMut(&[RoaringBitmap], &'t [u8]) -> Result<()>,
-    ) -> Result<Vec<grenad::Reader<File>>> {
+    ) -> Result<Vec<grenad::Reader<BufReader<File>>>> {
         if level == 0 {
             self.read_level_0(rtxn, field_id, handle_group)?;
             // Level 0 is already in the database

milli/src/update/facet/incremental.rs

@@ -1,5 +1,6 @@
 use std::collections::HashMap;
 use std::fs::File;
+use std::io::BufReader;
 
 use heed::types::{ByteSlice, DecodeIgnore};
 use heed::{BytesDecode, Error, RoTxn, RwTxn};
@@ -34,14 +35,14 @@ pub struct FacetsUpdateIncremental<'i> {
     index: &'i Index,
     inner: FacetsUpdateIncrementalInner,
     facet_type: FacetType,
-    new_data: grenad::Reader<File>,
+    new_data: grenad::Reader<BufReader<File>>,
 }
 
 impl<'i> FacetsUpdateIncremental<'i> {
     pub fn new(
         index: &'i Index,
         facet_type: FacetType,
-        new_data: grenad::Reader<File>,
+        new_data: grenad::Reader<BufReader<File>>,
         group_size: u8,
         min_level_size: u8,
         max_group_size: u8,

milli/src/update/facet/mod.rs

@@ -78,6 +78,7 @@ pub const FACET_MIN_LEVEL_SIZE: u8 = 5;
 
 use std::collections::BTreeSet;
 use std::fs::File;
+use std::io::BufReader;
 use std::iter::FromIterator;
 
 use charabia::normalizer::{Normalize, NormalizerOption};
@@ -108,13 +109,17 @@ pub struct FacetsUpdate<'i> {
     index: &'i Index,
     database: heed::Database<FacetGroupKeyCodec<ByteSliceRefCodec>, FacetGroupValueCodec>,
     facet_type: FacetType,
-    new_data: grenad::Reader<File>,
+    new_data: grenad::Reader<BufReader<File>>,
     group_size: u8,
     max_group_size: u8,
     min_level_size: u8,
 }
 impl<'i> FacetsUpdate<'i> {
-    pub fn new(index: &'i Index, facet_type: FacetType, new_data: grenad::Reader<File>) -> Self {
+    pub fn new(
+        index: &'i Index,
+        facet_type: FacetType,
+        new_data: grenad::Reader<BufReader<File>>,
+    ) -> Self {
         let database = match facet_type {
             FacetType::String => index
                 .facet_id_string_docids

milli/src/update/index_documents/enrich.rs

@@ -1,4 +1,4 @@
-use std::io::{Read, Seek};
+use std::io::{BufWriter, Read, Seek};
 use std::result::Result as StdResult;
 use std::{fmt, iter};
 
@@ -35,7 +35,7 @@ pub fn enrich_documents_batch<R: Read + Seek>(
 
     let (mut cursor, mut documents_batch_index) = reader.into_cursor_and_fields_index();
 
-    let mut external_ids = tempfile::tempfile().map(grenad::Writer::new)?;
+    let mut external_ids = tempfile::tempfile().map(BufWriter::new).map(grenad::Writer::new)?;
     let mut uuid_buffer = [0; uuid::fmt::Hyphenated::LENGTH];
 
     // The primary key *field id* that has already been set for this index or the one

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

@@ -1,6 +1,7 @@
 use std::collections::{HashMap, HashSet};
 use std::convert::TryInto;
 use std::fs::File;
+use std::io::BufReader;
 use std::{io, mem, str};
 
 use charabia::{Language, Script, SeparatorKind, Token, TokenKind, Tokenizer, TokenizerBuilder};
@@ -31,7 +32,7 @@ pub fn extract_docid_word_positions<R: io::Read + io::Seek>(
     allowed_separators: Option<&[&str]>,
     dictionary: Option<&[&str]>,
     max_positions_per_attributes: Option<u32>,
-) -> Result<(RoaringBitmap, grenad::Reader<File>, ScriptLanguageDocidsMap)> {
+) -> Result<(RoaringBitmap, grenad::Reader<BufReader<File>>, ScriptLanguageDocidsMap)> {
     puffin::profile_function!();
 
     let max_positions_per_attributes = max_positions_per_attributes

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

@@ -1,5 +1,5 @@
 use std::fs::File;
-use std::io;
+use std::io::{self, BufReader};
 
 use heed::{BytesDecode, BytesEncode};
 
@@ -19,7 +19,7 @@ use crate::Result;
 pub fn extract_facet_number_docids<R: io::Read + io::Seek>(
     docid_fid_facet_number: grenad::Reader<R>,
     indexer: GrenadParameters,
-) -> Result<grenad::Reader<File>> {
+) -> Result<grenad::Reader<BufReader<File>>> {
     puffin::profile_function!();
 
     let max_memory = indexer.max_memory_by_thread();

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

@@ -1,5 +1,5 @@
 use std::fs::File;
-use std::io;
+use std::io::{self, BufReader};
 
 use heed::BytesEncode;
 
@@ -17,7 +17,7 @@ use crate::{FieldId, Result, MAX_FACET_VALUE_LENGTH};
 pub fn extract_facet_string_docids<R: io::Read + io::Seek>(
     docid_fid_facet_string: grenad::Reader<R>,
     indexer: GrenadParameters,
-) -> Result<grenad::Reader<File>> {
+) -> Result<grenad::Reader<BufReader<File>>> {
     puffin::profile_function!();
 
     let max_memory = indexer.max_memory_by_thread();

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

@@ -1,7 +1,7 @@
 use std::collections::{BTreeMap, HashSet};
 use std::convert::TryInto;
 use std::fs::File;
-use std::io;
+use std::io::{self, BufReader};
 use std::mem::size_of;
 
 use heed::zerocopy::AsBytes;
@@ -17,11 +17,11 @@ use crate::{CboRoaringBitmapCodec, DocumentId, FieldId, Result, BEU32, MAX_FACET
 
 /// The extracted facet values stored in grenad files by type.
 pub struct ExtractedFacetValues {
-    pub docid_fid_facet_numbers_chunk: grenad::Reader<File>,
-    pub docid_fid_facet_strings_chunk: grenad::Reader<File>,
-    pub fid_facet_is_null_docids_chunk: grenad::Reader<File>,
-    pub fid_facet_is_empty_docids_chunk: grenad::Reader<File>,
-    pub fid_facet_exists_docids_chunk: grenad::Reader<File>,
+    pub docid_fid_facet_numbers_chunk: grenad::Reader<BufReader<File>>,
+    pub docid_fid_facet_strings_chunk: grenad::Reader<BufReader<File>>,
+    pub fid_facet_is_null_docids_chunk: grenad::Reader<BufReader<File>>,
+    pub fid_facet_is_empty_docids_chunk: grenad::Reader<BufReader<File>>,
+    pub fid_facet_exists_docids_chunk: grenad::Reader<BufReader<File>>,
 }
 
 /// Extracts the facet values of each faceted field of each document.

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

@@ -1,6 +1,6 @@
 use std::collections::HashMap;
 use std::fs::File;
-use std::io;
+use std::io::{self, BufReader};
 
 use grenad::Sorter;
 
@@ -21,7 +21,7 @@ use crate::{relative_from_absolute_position, DocumentId, FieldId, Result};
 pub fn extract_fid_word_count_docids<R: io::Read + io::Seek>(
     docid_word_positions: grenad::Reader<R>,
     indexer: GrenadParameters,
-) -> Result<grenad::Reader<File>> {
+) -> Result<grenad::Reader<BufReader<File>>> {
     puffin::profile_function!();
 
     let max_memory = indexer.max_memory_by_thread();

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

@@ -1,5 +1,5 @@
 use std::fs::File;
-use std::io;
+use std::io::{self, BufReader};
 
 use concat_arrays::concat_arrays;
 use serde_json::Value;
@@ -18,7 +18,7 @@ pub fn extract_geo_points<R: io::Read + io::Seek>(
     indexer: GrenadParameters,
     primary_key_id: FieldId,
     (lat_fid, lng_fid): (FieldId, FieldId),
-) -> Result<grenad::Reader<File>> {
+) -> Result<grenad::Reader<BufReader<File>>> {
     puffin::profile_function!();
 
     let mut writer = create_writer(

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

@@ -1,6 +1,6 @@
 use std::convert::TryFrom;
 use std::fs::File;
-use std::io;
+use std::io::{self, BufReader};
 
 use bytemuck::cast_slice;
 use serde_json::{from_slice, Value};
@@ -18,7 +18,7 @@ pub fn extract_vector_points<R: io::Read + io::Seek>(
     indexer: GrenadParameters,
     primary_key_id: FieldId,
     vectors_fid: FieldId,
-) -> Result<grenad::Reader<File>> {
+) -> Result<grenad::Reader<BufReader<File>>> {
     puffin::profile_function!();
 
     let mut writer = create_writer(

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

@@ -1,6 +1,6 @@
 use std::collections::HashSet;
 use std::fs::File;
-use std::io;
+use std::io::{self, BufReader};
 use std::iter::FromIterator;
 
 use roaring::RoaringBitmap;
@@ -26,7 +26,7 @@ pub fn extract_word_docids<R: io::Read + io::Seek>(
     docid_word_positions: grenad::Reader<R>,
     indexer: GrenadParameters,
     exact_attributes: &HashSet<FieldId>,
-) -> Result<(grenad::Reader<File>, grenad::Reader<File>)> {
+) -> Result<(grenad::Reader<BufReader<File>>, grenad::Reader<BufReader<File>>)> {
     puffin::profile_function!();
 
     let max_memory = indexer.max_memory_by_thread();

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

@@ -1,5 +1,5 @@
 use std::fs::File;
-use std::io;
+use std::io::{self, BufReader};
 
 use super::helpers::{
     create_sorter, merge_cbo_roaring_bitmaps, read_u32_ne_bytes, sorter_into_reader,
@@ -14,7 +14,7 @@ use crate::{relative_from_absolute_position, DocumentId, Result};
 pub fn extract_word_fid_docids<R: io::Read + io::Seek>(
     docid_word_positions: grenad::Reader<R>,
     indexer: GrenadParameters,
-) -> Result<grenad::Reader<File>> {
+) -> Result<grenad::Reader<BufReader<File>>> {
     puffin::profile_function!();
 
     let max_memory = indexer.max_memory_by_thread();

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

@@ -1,6 +1,7 @@
 use std::cmp::Ordering;
 use std::collections::{BinaryHeap, HashMap};
 use std::fs::File;
+use std::io::BufReader;
 use std::{cmp, io, mem, str, vec};
 
 use super::helpers::{
@@ -20,7 +21,7 @@ use crate::{DocumentId, Result};
 pub fn extract_word_pair_proximity_docids<R: io::Read + io::Seek>(
     docid_word_positions: grenad::Reader<R>,
     indexer: GrenadParameters,
-) -> Result<grenad::Reader<File>> {
+) -> Result<grenad::Reader<BufReader<File>>> {
     puffin::profile_function!();
 
     let max_memory = indexer.max_memory_by_thread();

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

@@ -1,5 +1,5 @@
 use std::fs::File;
-use std::io;
+use std::io::{self, BufReader};
 
 use super::helpers::{
     create_sorter, merge_cbo_roaring_bitmaps, read_u32_ne_bytes, sorter_into_reader,
@@ -17,7 +17,7 @@ use crate::{bucketed_position, relative_from_absolute_position, DocumentId, Resu
 pub fn extract_word_position_docids<R: io::Read + io::Seek>(
     docid_word_positions: grenad::Reader<R>,
     indexer: GrenadParameters,
-) -> Result<grenad::Reader<File>> {
+) -> Result<grenad::Reader<BufReader<File>>> {
     puffin::profile_function!();
 
     let max_memory = indexer.max_memory_by_thread();

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

@@ -12,6 +12,7 @@ mod extract_word_position_docids;
 
 use std::collections::HashSet;
 use std::fs::File;
+use std::io::BufReader;
 
 use crossbeam_channel::Sender;
 use log::debug;
@@ -39,8 +40,8 @@ use crate::{FieldId, Result};
 /// Send data in grenad file over provided Sender.
 #[allow(clippy::too_many_arguments)]
 pub(crate) fn data_from_obkv_documents(
-    original_obkv_chunks: impl Iterator<Item = Result<grenad::Reader<File>>> + Send,
-    flattened_obkv_chunks: impl Iterator<Item = Result<grenad::Reader<File>>> + Send,
+    original_obkv_chunks: impl Iterator<Item = Result<grenad::Reader<BufReader<File>>>> + Send,
+    flattened_obkv_chunks: impl Iterator<Item = Result<grenad::Reader<BufReader<File>>>> + Send,
     indexer: GrenadParameters,
     lmdb_writer_sx: Sender<Result<TypedChunk>>,
     searchable_fields: Option<HashSet<FieldId>>,
@@ -152,7 +153,7 @@ pub(crate) fn data_from_obkv_documents(
         });
     }
 
-    spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
+    spawn_extraction_task::<_, _, Vec<grenad::Reader<BufReader<File>>>>(
         docid_word_positions_chunks.clone(),
         indexer,
         lmdb_writer_sx.clone(),
@@ -162,7 +163,7 @@ pub(crate) fn data_from_obkv_documents(
         "word-pair-proximity-docids",
     );
 
-    spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
+    spawn_extraction_task::<_, _, Vec<grenad::Reader<BufReader<File>>>>(
         docid_word_positions_chunks.clone(),
         indexer,
         lmdb_writer_sx.clone(),
@@ -172,7 +173,11 @@ pub(crate) fn data_from_obkv_documents(
         "field-id-wordcount-docids",
     );
 
-    spawn_extraction_task::<_, _, Vec<(grenad::Reader<File>, grenad::Reader<File>)>>(
+    spawn_extraction_task::<
+        _,
+        _,
+        Vec<(grenad::Reader<BufReader<File>>, grenad::Reader<BufReader<File>>)>,
+    >(
         docid_word_positions_chunks.clone(),
         indexer,
         lmdb_writer_sx.clone(),
@@ -185,7 +190,7 @@ pub(crate) fn data_from_obkv_documents(
         "word-docids",
     );
 
-    spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
+    spawn_extraction_task::<_, _, Vec<grenad::Reader<BufReader<File>>>>(
         docid_word_positions_chunks.clone(),
         indexer,
         lmdb_writer_sx.clone(),
@@ -194,7 +199,7 @@ pub(crate) fn data_from_obkv_documents(
         TypedChunk::WordPositionDocids,
         "word-position-docids",
     );
-    spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
+    spawn_extraction_task::<_, _, Vec<grenad::Reader<BufReader<File>>>>(
         docid_word_positions_chunks,
         indexer,
         lmdb_writer_sx.clone(),
@@ -204,7 +209,7 @@ pub(crate) fn data_from_obkv_documents(
         "word-fid-docids",
     );
 
-    spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
+    spawn_extraction_task::<_, _, Vec<grenad::Reader<BufReader<File>>>>(
         docid_fid_facet_strings_chunks,
         indexer,
         lmdb_writer_sx.clone(),
@@ -214,7 +219,7 @@ pub(crate) fn data_from_obkv_documents(
         "field-id-facet-string-docids",
     );
 
-    spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
+    spawn_extraction_task::<_, _, Vec<grenad::Reader<BufReader<File>>>>(
         docid_fid_facet_numbers_chunks,
         indexer,
         lmdb_writer_sx,
@@ -269,7 +274,7 @@ fn spawn_extraction_task<FE, FS, M>(
 /// Extract chunked data and send it into lmdb_writer_sx sender:
 /// - documents
 fn send_original_documents_data(
-    original_documents_chunk: Result<grenad::Reader<File>>,
+    original_documents_chunk: Result<grenad::Reader<BufReader<File>>>,
     indexer: GrenadParameters,
     lmdb_writer_sx: Sender<Result<TypedChunk>>,
     vectors_field_id: Option<FieldId>,
@@ -311,7 +316,7 @@ fn send_original_documents_data(
 #[allow(clippy::too_many_arguments)]
 #[allow(clippy::type_complexity)]
 fn send_and_extract_flattened_documents_data(
-    flattened_documents_chunk: Result<grenad::Reader<File>>,
+    flattened_documents_chunk: Result<grenad::Reader<BufReader<File>>>,
     indexer: GrenadParameters,
     lmdb_writer_sx: Sender<Result<TypedChunk>>,
     searchable_fields: &Option<HashSet<FieldId>>,
@@ -328,7 +333,10 @@ fn send_and_extract_flattened_documents_data(
         grenad::Reader<CursorClonableMmap>,
         (
             grenad::Reader<CursorClonableMmap>,
-            (grenad::Reader<File>, (grenad::Reader<File>, grenad::Reader<File>)),
+            (
+                grenad::Reader<BufReader<File>>,
+                (grenad::Reader<BufReader<File>>, grenad::Reader<BufReader<File>>),
+            ),
         ),
     ),
 )> {

milli/src/update/index_documents/helpers/grenad_helpers.rs

@@ -1,6 +1,6 @@
 use std::borrow::Cow;
 use std::fs::File;
-use std::io::{self, Seek};
+use std::io::{self, BufReader, BufWriter, Seek};
 use std::time::Instant;
 
 use grenad::{CompressionType, Sorter};
@@ -17,13 +17,13 @@ pub fn create_writer<R: io::Write>(
     typ: grenad::CompressionType,
     level: Option<u32>,
     file: R,
-) -> grenad::Writer<R> {
+) -> grenad::Writer<BufWriter<R>> {
     let mut builder = grenad::Writer::builder();
     builder.compression_type(typ);
     if let Some(level) = level {
         builder.compression_level(level);
     }
-    builder.build(file)
+    builder.build(BufWriter::new(file))
 }
 
 pub fn create_sorter(
@@ -53,7 +53,7 @@ pub fn create_sorter(
 pub fn sorter_into_reader(
     sorter: grenad::Sorter<MergeFn>,
     indexer: GrenadParameters,
-) -> Result<grenad::Reader<File>> {
+) -> Result<grenad::Reader<BufReader<File>>> {
     let mut writer = create_writer(
         indexer.chunk_compression_type,
         indexer.chunk_compression_level,
@@ -64,16 +64,18 @@ pub fn sorter_into_reader(
     writer_into_reader(writer)
 }
 
-pub fn writer_into_reader(writer: grenad::Writer<File>) -> Result<grenad::Reader<File>> {
-    let mut file = writer.into_inner()?;
+pub fn writer_into_reader(
+    writer: grenad::Writer<BufWriter<File>>,
+) -> Result<grenad::Reader<BufReader<File>>> {
+    let mut file = writer.into_inner()?.into_inner().map_err(|err| err.into_error())?;
     file.rewind()?;
-    grenad::Reader::new(file).map_err(Into::into)
+    grenad::Reader::new(BufReader::new(file)).map_err(Into::into)
 }
 
 pub unsafe fn as_cloneable_grenad(
-    reader: &grenad::Reader<File>,
+    reader: &grenad::Reader<BufReader<File>>,
 ) -> Result<grenad::Reader<CursorClonableMmap>> {
-    let file = reader.get_ref();
+    let file = reader.get_ref().get_ref();
     let mmap = memmap2::Mmap::map(file)?;
     let cursor = io::Cursor::new(ClonableMmap::from(mmap));
     let reader = grenad::Reader::new(cursor)?;
@@ -89,8 +91,8 @@ where
     fn merge(self, merge_fn: MergeFn, indexer: &GrenadParameters) -> Result<Self::Output>;
 }
 
-impl MergeableReader for Vec<grenad::Reader<File>> {
-    type Output = grenad::Reader<File>;
+impl MergeableReader for Vec<grenad::Reader<BufReader<File>>> {
+    type Output = grenad::Reader<BufReader<File>>;
 
     fn merge(self, merge_fn: MergeFn, params: &GrenadParameters) -> Result<Self::Output> {
         let mut merger = MergerBuilder::new(merge_fn);
@@ -99,8 +101,8 @@ impl MergeableReader for Vec<grenad::Reader<File>> {
     }
 }
 
-impl MergeableReader for Vec<(grenad::Reader<File>, grenad::Reader<File>)> {
-    type Output = (grenad::Reader<File>, grenad::Reader<File>);
+impl MergeableReader for Vec<(grenad::Reader<BufReader<File>>, grenad::Reader<BufReader<File>>)> {
+    type Output = (grenad::Reader<BufReader<File>>, grenad::Reader<BufReader<File>>);
 
     fn merge(self, merge_fn: MergeFn, params: &GrenadParameters) -> Result<Self::Output> {
         let mut m1 = MergerBuilder::new(merge_fn);
@@ -125,7 +127,7 @@ impl<R: io::Read + io::Seek> MergerBuilder<R> {
         Ok(())
     }
 
-    fn finish(self, params: &GrenadParameters) -> Result<grenad::Reader<File>> {
+    fn finish(self, params: &GrenadParameters) -> Result<grenad::Reader<BufReader<File>>> {
         let merger = self.0.build();
         let mut writer = create_writer(
             params.chunk_compression_type,
@@ -176,7 +178,7 @@ pub fn grenad_obkv_into_chunks<R: io::Read + io::Seek>(
     reader: grenad::Reader<R>,
     indexer: GrenadParameters,
     documents_chunk_size: usize,
-) -> Result<impl Iterator<Item = Result<grenad::Reader<File>>>> {
+) -> Result<impl Iterator<Item = Result<grenad::Reader<BufReader<File>>>>> {
     let mut continue_reading = true;
     let mut cursor = reader.into_cursor()?;
 

milli/src/update/index_documents/transform.rs

@@ -659,8 +659,10 @@ impl<'a, 'i> Transform<'a, 'i> {
             new_documents_ids: self.new_documents_ids,
             replaced_documents_ids: self.replaced_documents_ids,
             documents_count: self.documents_count,
-            original_documents,
-            flattened_documents,
+            original_documents: original_documents.into_inner().map_err(|err| err.into_error())?,
+            flattened_documents: flattened_documents
+                .into_inner()
+                .map_err(|err| err.into_error())?,
         })
     }
 
@@ -779,8 +781,10 @@ impl<'a, 'i> Transform<'a, 'i> {
             new_documents_ids: documents_ids,
             replaced_documents_ids: RoaringBitmap::default(),
             documents_count,
-            original_documents,
-            flattened_documents,
+            original_documents: original_documents.into_inner().map_err(|err| err.into_error())?,
+            flattened_documents: flattened_documents
+                .into_inner()
+                .map_err(|err| err.into_error())?,
         };
 
         let new_facets = output.compute_real_facets(wtxn, self.index)?;

milli/src/update/index_documents/typed_chunk.rs

@@ -2,7 +2,7 @@ use std::borrow::Cow;
 use std::collections::HashMap;
 use std::convert::TryInto;
 use std::fs::File;
-use std::io;
+use std::io::{self, BufReader};
 
 use bytemuck::allocation::pod_collect_to_vec;
 use charabia::{Language, Script};
@@ -27,22 +27,22 @@ pub(crate) enum TypedChunk {
     FieldIdDocidFacetStrings(grenad::Reader<CursorClonableMmap>),
     FieldIdDocidFacetNumbers(grenad::Reader<CursorClonableMmap>),
     Documents(grenad::Reader<CursorClonableMmap>),
-    FieldIdWordcountDocids(grenad::Reader<File>),
+    FieldIdWordcountDocids(grenad::Reader<BufReader<File>>),
     NewDocumentsIds(RoaringBitmap),
     WordDocids {
-        word_docids_reader: grenad::Reader<File>,
-        exact_word_docids_reader: grenad::Reader<File>,
+        word_docids_reader: grenad::Reader<BufReader<File>>,
+        exact_word_docids_reader: grenad::Reader<BufReader<File>>,
     },
-    WordPositionDocids(grenad::Reader<File>),
-    WordFidDocids(grenad::Reader<File>),
-    WordPairProximityDocids(grenad::Reader<File>),
-    FieldIdFacetStringDocids(grenad::Reader<File>),
-    FieldIdFacetNumberDocids(grenad::Reader<File>),
-    FieldIdFacetExistsDocids(grenad::Reader<File>),
-    FieldIdFacetIsNullDocids(grenad::Reader<File>),
-    FieldIdFacetIsEmptyDocids(grenad::Reader<File>),
-    GeoPoints(grenad::Reader<File>),
-    VectorPoints(grenad::Reader<File>),
+    WordPositionDocids(grenad::Reader<BufReader<File>>),
+    WordFidDocids(grenad::Reader<BufReader<File>>),
+    WordPairProximityDocids(grenad::Reader<BufReader<File>>),
+    FieldIdFacetStringDocids(grenad::Reader<BufReader<File>>),
+    FieldIdFacetNumberDocids(grenad::Reader<BufReader<File>>),
+    FieldIdFacetExistsDocids(grenad::Reader<BufReader<File>>),
+    FieldIdFacetIsNullDocids(grenad::Reader<BufReader<File>>),
+    FieldIdFacetIsEmptyDocids(grenad::Reader<BufReader<File>>),
+    GeoPoints(grenad::Reader<BufReader<File>>),
+    VectorPoints(grenad::Reader<BufReader<File>>),
     ScriptLanguageDocids(HashMap<(Script, Language), RoaringBitmap>),
 }
 

milli/src/update/prefix_word_pairs/mod.rs

@@ -1,6 +1,6 @@
 use std::borrow::Cow;
 use std::collections::HashSet;
-use std::io::BufReader;
+use std::io::{BufReader, BufWriter};
 
 use grenad::CompressionType;
 use heed::types::ByteSlice;
@@ -119,9 +119,9 @@ pub fn insert_into_database(
 pub fn write_into_lmdb_database_without_merging(
     wtxn: &mut heed::RwTxn,
     database: heed::PolyDatabase,
-    writer: grenad::Writer<std::fs::File>,
+    writer: grenad::Writer<BufWriter<std::fs::File>>,
 ) -> Result<()> {
-    let file = writer.into_inner()?;
+    let file = writer.into_inner()?.into_inner().map_err(|err| err.into_error())?;
     let reader = grenad::Reader::new(BufReader::new(file))?;
     if database.is_empty(wtxn)? {
         let mut out_iter = database.iter_mut::<_, ByteSlice, ByteSlice>(wtxn)?;

milli/tests/search/distinct.rs

@@ -8,7 +8,7 @@ use Criterion::*;
 use crate::search::{self, EXTERNAL_DOCUMENTS_IDS};
 
 macro_rules! test_distinct {
-    ($func:ident, $distinct:ident, $exhaustive:ident, $limit:expr, $criteria:expr, $n_res:expr) => {
+    ($func:ident, $distinct:ident, $exhaustive:ident, $limit:expr, $offset:expr, $criteria:expr, $n_res:expr) => {
         #[test]
         fn $func() {
             let criteria = $criteria;
@@ -27,6 +27,7 @@ macro_rules! test_distinct {
             let mut search = Search::new(&rtxn, &index);
             search.query(search::TEST_QUERY);
             search.limit($limit);
+            search.offset($offset);
             search.exhaustive_number_hits($exhaustive);
 
             search.terms_matching_strategy(TermsMatchingStrategy::default());
@@ -47,6 +48,7 @@ macro_rules! test_distinct {
                             Some(d.id)
                         }
                     })
+                    .skip($offset)
                     .take($limit)
                     .collect();
 
@@ -61,6 +63,7 @@ test_distinct!(
     tag,
     true,
     1,
+    0,
     vec![Words, Typo, Proximity, Attribute, Exactness],
     3
 );
@@ -69,6 +72,7 @@ test_distinct!(
     asc_desc_rank,
     true,
     1,
+    0,
     vec![Words, Typo, Proximity, Attribute, Exactness],
     7
 );
@@ -77,6 +81,7 @@ test_distinct!(
     asc_desc_rank,
     true,
     0,
+    0,
     vec![Desc(S("attribute_rank")), Desc(S("exactness_rank")), Exactness, Typo],
     7
 );
@@ -86,6 +91,7 @@ test_distinct!(
     tag,
     false,
     EXTERNAL_DOCUMENTS_IDS.len(),
+    0,
     vec![Words, Typo, Proximity, Attribute, Exactness],
     3
 );
@@ -94,6 +100,7 @@ test_distinct!(
     asc_desc_rank,
     false,
     EXTERNAL_DOCUMENTS_IDS.len(),
+    0,
     vec![Words, Typo, Proximity, Attribute, Exactness],
     7
 );
@@ -102,6 +109,7 @@ test_distinct!(
     tag,
     false,
     EXTERNAL_DOCUMENTS_IDS.len(),
+    0,
     vec![Words],
     3
 );
@@ -110,6 +118,7 @@ test_distinct!(
     asc_desc_rank,
     false,
     EXTERNAL_DOCUMENTS_IDS.len(),
+    0,
     vec![Words],
     7
 );
@@ -118,6 +127,7 @@ test_distinct!(
     tag,
     false,
     EXTERNAL_DOCUMENTS_IDS.len(),
+    0,
     vec![Words, Typo],
     3
 );
@@ -126,6 +136,7 @@ test_distinct!(
     asc_desc_rank,
     false,
     EXTERNAL_DOCUMENTS_IDS.len(),
+    0,
     vec![Words, Typo],
     7
 );
@@ -134,6 +145,7 @@ test_distinct!(
     tag,
     false,
     EXTERNAL_DOCUMENTS_IDS.len(),
+    0,
     vec![Words, Proximity],
     3
 );
@@ -142,6 +154,7 @@ test_distinct!(
     asc_desc_rank,
     false,
     EXTERNAL_DOCUMENTS_IDS.len(),
+    0,
     vec![Words, Proximity],
     7
 );
@@ -150,6 +163,7 @@ test_distinct!(
     tag,
     false,
     EXTERNAL_DOCUMENTS_IDS.len(),
+    0,
     vec![Words, Attribute],
     3
 );
@@ -158,6 +172,7 @@ test_distinct!(
     asc_desc_rank,
     false,
     EXTERNAL_DOCUMENTS_IDS.len(),
+    0,
     vec![Words, Attribute],
     7
 );
@@ -166,6 +181,7 @@ test_distinct!(
     tag,
     false,
     EXTERNAL_DOCUMENTS_IDS.len(),
+    0,
     vec![Words, Exactness],
     3
 );
@@ -174,6 +190,47 @@ test_distinct!(
     asc_desc_rank,
     false,
     EXTERNAL_DOCUMENTS_IDS.len(),
+    0,
     vec![Words, Exactness],
     7
 );
+test_distinct!(
+    // testing: https://github.com/meilisearch/meilisearch/issues/4078
+    distinct_string_limit_and_offset,
+    tag,
+    false,
+    EXTERNAL_DOCUMENTS_IDS.len(),
+    1,
+    vec![],
+    3
+);
+test_distinct!(
+    // testing: https://github.com/meilisearch/meilisearch/issues/4078
+    exhaustive_distinct_string_limit_and_offset,
+    tag,
+    true,
+    1,
+    2,
+    vec![],
+    3
+);
+test_distinct!(
+    // testing: https://github.com/meilisearch/meilisearch/issues/4078
+    distinct_number_limit_and_offset,
+    asc_desc_rank,
+    false,
+    EXTERNAL_DOCUMENTS_IDS.len(),
+    2,
+    vec![],
+    7
+);
+test_distinct!(
+    // testing: https://github.com/meilisearch/meilisearch/issues/4078
+    exhaustive_distinct_number_limit_and_offset,
+    asc_desc_rank,
+    true,
+    2,
+    4,
+    vec![],
+    7
+);