implement placeholder search

errors.yaml

@@ -0,0 +1,51 @@
+---
+errors:
+  - code: create_index
+    description: "Error relatice to index creation, check out our guide on [index creation](link.com)"
+  - code: existing_index
+    description: "An index with this name already exists, check out our guide on [index creation](link.com)"
+  - code: invalid_index_uid
+    description: "The provided index formatting is wrong, check out our guide on [index creation](link.com)"
+  - code: open_index
+    description: "An error occured while trying to open the requested index, ..."
+  - code: invalid_state
+    description: ""
+  - code: missing_primary_key
+    description: ""
+  - code: primary_key_already_present
+    description: ""
+  - code: max_field_limit_exceeded
+    description: ""
+  - code: missing_document_id
+    description: ""
+  - code: invalid_facet
+    description: ""
+  - code: invalid_filter
+    description: ""
+  - code: bad_parameter
+    description: ""
+  - code: bad_request
+    description: ""
+  - code: document_not_found
+    description: ""
+  - code: internal
+    description: ""
+  - code: invalid_token
+    description: ""
+  - code: maintenance
+    description: ""
+  - code: missing_authorization_header
+    description: ""
+  - code: missing_header
+    description: ""
+  - code: not_found
+    description: ""
+  - code: payload_too_large
+    description: ""
+  - code: retrieve_document
+    description: ""
+  - code: search_error
+    description: ""
+  - code: unsupported_media_type
+    description: ""
+...

meilisearch-core/examples/from_file.rs

@@ -368,7 +368,7 @@ fn search_command(command: SearchCommand, database: Database) -> Result<(), Box<
                     });
                 }
 
-                let result = builder.query(ref_reader, &query, 0..command.number_results)?;
+                let result = builder.query(ref_reader, Some(&query), 0..command.number_results)?;
 
                 let mut retrieve_duration = Duration::default();
 

meilisearch-core/src/bucket_sort.rs

@@ -10,16 +10,16 @@ use std::fmt;
 
 use compact_arena::{SmallArena, Idx32, mk_arena};
 use log::debug;
-use meilisearch_types::DocIndex;
 use sdset::{Set, SetBuf, exponential_search, SetOperation, Counter, duo::OpBuilder};
 use slice_group_by::{GroupBy, GroupByMut};
 
-use crate::error::Error;
+use meilisearch_types::DocIndex;
+
 use crate::criterion::{Criteria, Context, ContextMut};
 use crate::distinct_map::{BufferedDistinctMap, DistinctMap};
 use crate::raw_document::RawDocument;
 use crate::{database::MainT, reordered_attrs::ReorderedAttrs};
-use crate::{Document, DocumentId, MResult, Index};
+use crate::{store, Document, DocumentId, MResult, Index, RankedMap, MainReader, Error};
 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;
@@ -588,8 +588,55 @@ impl Deref for PostingsListView<'_> {
     }
 }
 
+/// sorts documents ids according to user defined ranking rules.
+pub fn placeholder_document_sort(
+    document_ids: &mut [DocumentId],
+    index: &store::Index,
+    reader: &MainReader,
+    ranked_map: &RankedMap
+) -> MResult<()> {
+    use crate::settings::RankingRule;
+    use std::cmp::Ordering;
+
+    enum SortOrder {
+        Asc,
+        Desc,
+    }
+
+    if let Some(ranking_rules) = index.main.ranking_rules(reader)? {
+        let schema = index.main.schema(reader)?
+            .ok_or(Error::SchemaMissing)?;
+
+        // Select custom rules from ranking rules, and map them to custom rules
+        // containing a field_id
+        let ranking_rules = ranking_rules.iter().filter_map(|r|
+            match r {
+                RankingRule::Asc(name) => schema.id(name).map(|f| (f, SortOrder::Asc)),
+                RankingRule::Desc(name) => schema.id(name).map(|f| (f, SortOrder::Desc)),
+                _ => None,
+            }).collect::<Vec<_>>();
+
+        document_ids.sort_unstable_by(|a, b| {
+            for (field_id, order) in &ranking_rules {
+                let a_value = ranked_map.get(*a, *field_id);
+                let b_value = ranked_map.get(*b, *field_id);
+                let (a, b) = match order {
+                    SortOrder::Asc => (a_value, b_value),
+                    SortOrder::Desc => (b_value, a_value),
+                };
+                match a.cmp(&b) {
+                    Ordering::Equal => continue,
+                    ordering => return ordering,
+                }
+            }
+            Ordering::Equal
+        });
+    }
+    Ok(())
+}
+
 /// For each entry in facet_docids, calculates the number of documents in the intersection with candidate_docids.
-fn facet_count(
+pub fn facet_count(
     facet_docids: HashMap<String, HashMap<String, Cow<Set<DocumentId>>>>,
     candidate_docids: &Set<DocumentId>,
 ) -> HashMap<String, HashMap<String, usize>> {

meilisearch-core/src/database.rs

@@ -814,7 +814,7 @@ mod tests {
 
         // even try to search for a document
         let reader = db.main_read_txn().unwrap();
-        let SortResult {documents, .. } = index.query_builder().query(&reader, "21 ", 0..20).unwrap();
+        let SortResult {documents, .. } = index.query_builder().query(&reader, Some("21 "), 0..20).unwrap();
         assert_matches!(documents.len(), 1);
 
         reader.abort().unwrap();
@@ -1212,7 +1212,7 @@ mod tests {
 
         let builder = index.query_builder_with_criteria(criteria);
 
-        let SortResult {documents, .. } = builder.query(&reader, "Kevin", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, Some("Kevin"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(

meilisearch-core/src/query_builder.rs

@@ -1,18 +1,20 @@
 use std::borrow::Cow;
 use std::collections::HashMap;
-use std::ops::{Range, Deref};
+use std::ops::{Deref, Range};
 use std::time::Duration;
 
 use either::Either;
-use sdset::SetOperation;
+use sdset::{SetOperation, SetBuf, Set};
 
 use meilisearch_schema::FieldId;
 
+use crate::bucket_sort::{bucket_sort, bucket_sort_with_distinct, SortResult, placeholder_document_sort, facet_count};
 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;
+use crate::distinct_map::{DistinctMap, BufferedDistinctMap};
+use crate::Document;
+use crate::{criterion::Criteria, DocumentId};
+use crate::{reordered_attrs::ReorderedAttrs, store, MResult, MainReader};
 
 pub struct QueryBuilder<'c, 'f, 'd, 'i> {
     criteria: Criteria<'c>,
@@ -27,10 +29,7 @@ pub struct QueryBuilder<'c, 'f, 'd, 'i> {
 
 impl<'c, 'f, 'd, 'i> QueryBuilder<'c, 'f, 'd, 'i> {
     pub fn new(index: &'i store::Index) -> Self {
-        QueryBuilder::with_criteria(
-            index,
-            Criteria::default(),
-        )
+        QueryBuilder::with_criteria(index, Criteria::default())
     }
 
     /// sets facet attributes to filter on
@@ -43,10 +42,7 @@ impl<'c, 'f, 'd, 'i> QueryBuilder<'c, 'f, 'd, 'i> {
         self.facets = facets;
     }
 
-    pub fn with_criteria(
-        index: &'i store::Index,
-        criteria: Criteria<'c>,
-    ) -> Self {
+    pub fn with_criteria(index: &'i store::Index, criteria: Criteria<'c>) -> Self {
         QueryBuilder {
             criteria,
             searchable_attrs: None,
@@ -82,14 +78,11 @@ impl<'c, 'f, 'd, 'i> QueryBuilder<'c, 'f, 'd, 'i> {
         reorders.insert_attribute(attribute);
     }
 
-    pub fn query(
-        self,
-        reader: &heed::RoTxn<MainT>,
-        query: &str,
-        range: Range<usize>,
-    ) -> MResult<SortResult> {
-        let facets_docids = match self.facet_filter {
-            Some(facets) => {
+    /// returns the documents ids associated with a facet filter by computing the union and
+    /// intersection of the document sets
+    fn facets_docids(&self, reader: &MainReader) -> MResult<Option<SetBuf<DocumentId>>> {
+        let facet_docids = match self.facet_filter {
+            Some(ref facets) => {
                 let mut ands = Vec::with_capacity(facets.len());
                 let mut ors = Vec::new();
                 for f in facets.deref() {
@@ -97,48 +90,50 @@ impl<'c, 'f, 'd, 'i> QueryBuilder<'c, 'f, 'd, 'i> {
                         Either::Left(keys) => {
                             ors.reserve(keys.len());
                             for key in keys {
-                                let docids = self.index.facets.facet_document_ids(reader, &key)?.unwrap_or_default();
+                                let docids = self
+                                    .index
+                                    .facets
+                                    .facet_document_ids(reader, &key)?
+                                    .unwrap_or_default();
                                 ors.push(docids);
                             }
                             let sets: Vec<_> = ors.iter().map(Cow::deref).collect();
-                            let or_result = sdset::multi::OpBuilder::from_vec(sets).union().into_set_buf();
+                            let or_result = sdset::multi::OpBuilder::from_vec(sets)
+                                .union()
+                                .into_set_buf();
                             ands.push(Cow::Owned(or_result));
                             ors.clear();
                         }
-                        Either::Right(key) =>{
+                        Either::Right(key) => {
                             match self.index.facets.facet_document_ids(reader, &key)? {
                                 Some(docids) => ands.push(docids),
                                 // no candidates for search, early return.
-                                None => return Ok(SortResult::default()),
+                                None => return Ok(Some(SetBuf::default())),
                             }
                         }
                     };
                 }
                 let ands: Vec<_> = ands.iter().map(Cow::deref).collect();
-                Some(sdset::multi::OpBuilder::from_vec(ands).intersection().into_set_buf())
-            }
-            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)
+                Some(
+                    sdset::multi::OpBuilder::from_vec(ands)
+                    .intersection()
+                    .into_set_buf(),
+                )
             }
             None => None,
         };
+        Ok(facet_docids)
+    }
+
+    fn standard_query(self, reader: &MainReader, query: &str, range: Range<usize>) -> MResult<SortResult> {
+        let facets_docids = match self.facets_docids(reader)? {
+            Some(ids) if ids.is_empty() => return Ok(SortResult::default()),
+            other => other
+        };
+        // 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 = self.facet_count_docids(reader)?;
 
         match self.distinct {
             Some((distinct, distinct_size)) => bucket_sort_with_distinct(
@@ -167,6 +162,117 @@ impl<'c, 'f, 'd, 'i> QueryBuilder<'c, 'f, 'd, 'i> {
             ),
         }
     }
+
+    fn placeholder_query(self, reader: &heed::RoTxn<MainT>, range: Range<usize>) -> MResult<SortResult> {
+        match self.facets_docids(reader)? {
+            Some(docids) => {
+                // We sort the docids from facets according to the criteria set by the user
+                let mut sorted_docids = docids.clone().into_vec();
+                let mut sort_result = match self.index.main.ranked_map(reader)? {
+                    Some(ranked_map) => {
+                        placeholder_document_sort(&mut sorted_docids, self.index, reader, &ranked_map)?;
+                        self.sort_result_from_docids(&sorted_docids, range)
+                    },
+                    // if we can't perform a sort, we return documents unordered
+                    None => self.sort_result_from_docids(&docids, range),
+                };
+
+                if let Some(f) = self.facet_count_docids(reader)? {
+                    sort_result.exhaustive_facets_count = Some(true);
+                    sort_result.facets = Some(facet_count(f, &docids));
+                }
+
+                Ok(sort_result)
+            },
+            None => {
+                match self.index.main.sorted_document_ids_cache(reader)? {
+                    // build result from cached document ids
+                    Some(docids) => {
+                        let mut sort_result = self.sort_result_from_docids(&docids, range);
+
+                        if let Some(f) = self.facet_count_docids(reader)? {
+                            sort_result.exhaustive_facets_count = Some(true);
+                            // document ids are not sorted in natural order, we need to construct a new set
+                            let document_set = SetBuf::from_dirty(Vec::from(docids));
+                            sort_result.facets = Some(facet_count(f, &document_set));
+                        }
+
+                        Ok(sort_result)
+                    },
+                    // no document id cached, return empty result
+                    None => Ok(SortResult::default()),
+                }
+            }
+        }
+    }
+
+    fn facet_count_docids<'a>(&self, reader: &'a MainReader) -> MResult<Option<HashMap<String, HashMap<String, Cow<'a, Set<DocumentId>>>>>> {
+        match self.facets {
+            Some(ref 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.clone(), key_map);
+                }
+                Ok(Some(facet_count_map))
+            }
+            None => Ok(None),
+        }
+    }
+
+    fn sort_result_from_docids(&self, docids: &[DocumentId], range: Range<usize>) -> SortResult {
+        let mut sort_result = SortResult::default();
+        let mut result = match self.filter {
+            Some(ref filter) => docids
+                .iter()
+                .filter(|item| (filter)(**item))
+                .skip(range.start)
+                .take(range.end - range.start)
+                .map(|&id| Document::from_highlights(id, &[]))
+                .collect::<Vec<_>>(),
+            None => docids
+                .iter()
+                .skip(range.start)
+                .take(range.end - range.start)
+                .map(|&id| Document::from_highlights(id, &[]))
+                .collect::<Vec<_>>(),
+        };
+
+        // distinct is set, remove duplicates with disctinct function
+        if let Some((distinct, distinct_size)) = &self.distinct {
+            let mut distinct_map = DistinctMap::new(*distinct_size);
+            let mut distinct_map = BufferedDistinctMap::new(&mut distinct_map);
+            result.retain(|doc| {
+                let id = doc.id;
+                let key = (distinct)(id);
+                match key {
+                    Some(key) => distinct_map.register(key),
+                    None => distinct_map.register_without_key(),
+                }
+            });
+        }
+
+        sort_result.documents = result;
+        sort_result.nb_hits = docids.len();
+        sort_result
+    }
+
+    pub fn query(
+        self,
+        reader: &heed::RoTxn<MainT>,
+        query: Option<&str>,
+        range: Range<usize>,
+    ) -> MResult<SortResult> {
+        match query {
+            Some(query) => self.standard_query(reader, query, range),
+            None => self.placeholder_query(reader, range),
+        }
+    }
 }
 
 #[cfg(test)]
@@ -181,12 +287,12 @@ mod tests {
     use sdset::SetBuf;
     use tempfile::TempDir;
 
-    use crate::DocIndex;
-    use crate::Document;
     use crate::automaton::normalize_str;
     use crate::bucket_sort::SimpleMatch;
-    use crate::database::{Database,DatabaseOptions};
+    use crate::database::{Database, DatabaseOptions};
     use crate::store::Index;
+    use crate::DocIndex;
+    use crate::Document;
     use meilisearch_schema::Schema;
 
     fn set_from_stream<'f, I, S>(stream: I) -> fst::Set<Vec<u8>>
@@ -366,7 +472,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult { documents, .. } = builder.query(&reader, "iphone from apple", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("iphone from apple"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -389,7 +495,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult { documents, .. } = builder.query(&reader, "hello", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("hello"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -400,7 +506,7 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let SortResult { documents, .. } = builder.query(&reader, "bonjour", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("bonjour"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -504,7 +610,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult { documents, .. } = builder.query(&reader, "hello", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("hello"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -525,7 +631,7 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let SortResult { documents, .. } = builder.query(&reader, "bonjour", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("bonjour"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -546,7 +652,7 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let SortResult { documents, .. } = builder.query(&reader, "salut", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("salut"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -592,7 +698,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult { documents, .. } = builder.query(&reader, "NY subway", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("NY subway"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
@@ -614,7 +720,7 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let SortResult { documents, .. } = builder.query(&reader, "NYC subway", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("NYC subway"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
@@ -656,7 +762,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "NY", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("NY"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(2), matches, .. }) => {
@@ -680,7 +786,7 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "new york", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("new york"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -714,7 +820,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "NY subway", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("NY subway"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -731,7 +837,8 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "new york subway", 0..20).unwrap();
+        let SortResult { documents, .. } =
+            builder.query(&reader, Some("new york subway"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
@@ -779,7 +886,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "NY subway", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("NY subway"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
@@ -801,7 +908,7 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "NYC subway", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("NYC subway"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
@@ -854,7 +961,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "NY subway broken", 0..20).unwrap();
+        let SortResult {documents, .. } = builder.query(&reader, Some("NY subway broken"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -870,7 +977,7 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "NYC subway", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("NYC subway"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
@@ -926,8 +1033,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder
-            .query(&reader, "new york underground train broken", 0..20)
+        let SortResult { documents, .. } = builder
+            .query(&reader, Some("new york underground train broken"), 0..20)
             .unwrap();
         let mut iter = documents.into_iter();
 
@@ -956,8 +1063,8 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder
-            .query(&reader, "new york city underground train broken", 0..20)
+        let SortResult { documents, .. } = builder
+            .query(&reader, Some("new york city underground train broken"), 0..20)
             .unwrap();
         let mut iter = documents.into_iter();
 
@@ -1000,7 +1107,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "new york big ", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("new york big "), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -1034,7 +1141,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "NY subway ", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("NY subway "), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -1084,8 +1191,8 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder
-            .query(&reader, "new york city long subway cool ", 0..20)
+        let SortResult { documents, .. } = builder
+            .query(&reader, Some("new york city long subway cool "), 0..20)
             .unwrap();
         let mut iter = documents.into_iter();
 
@@ -1117,7 +1224,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "telephone", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("telephone"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -1134,7 +1241,7 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "téléphone", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("téléphone"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -1151,7 +1258,7 @@ mod tests {
         assert_matches!(iter.next(), None);
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "télephone", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("télephone"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(1), matches, .. }) => {
@@ -1178,7 +1285,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "i phone case", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("i phone case"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -1207,7 +1314,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "searchengine", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("searchengine"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -1247,7 +1354,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "searchengine", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("searchengine"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {
@@ -1279,7 +1386,7 @@ mod tests {
         let reader = db.main_read_txn().unwrap();
 
         let builder = store.query_builder();
-        let SortResult {documents, .. } = builder.query(&reader, "searchengine", 0..20).unwrap();
+        let SortResult { documents, .. } = builder.query(&reader, Some("searchengine"), 0..20).unwrap();
         let mut iter = documents.into_iter();
 
         assert_matches!(iter.next(), Some(Document { id: DocumentId(0), matches, .. }) => {

meilisearch-core/src/store/main.rs

@@ -2,7 +2,7 @@ use std::borrow::Cow;
 use std::collections::HashMap;
 
 use chrono::{DateTime, Utc};
-use heed::types::{ByteSlice, OwnedType, SerdeBincode, Str};
+use heed::types::{ByteSlice, OwnedType, SerdeBincode, Str, CowSlice};
 use meilisearch_schema::{FieldId, Schema};
 use meilisearch_types::DocumentId;
 use sdset::Set;
@@ -25,6 +25,7 @@ const NUMBER_OF_DOCUMENTS_KEY: &str = "number-of-documents";
 const RANKED_MAP_KEY: &str = "ranked-map";
 const RANKING_RULES_KEY: &str = "ranking-rules";
 const SCHEMA_KEY: &str = "schema";
+const SORTED_DOCUMENT_IDS_CACHE_KEY: &str = "sorted-document-ids-cache";
 const STOP_WORDS_KEY: &str = "stop-words";
 const SYNONYMS_KEY: &str = "synonyms";
 const UPDATED_AT_KEY: &str = "updated-at";
@@ -165,6 +166,14 @@ impl Main {
         Ok(self.main.put::<_, Str, ByteSlice>(writer, WORDS_KEY, fst.as_fst().as_bytes())?)
     }
 
+    pub fn put_sorted_document_ids_cache(self, writer: &mut heed::RwTxn<MainT>, documents_ids: &[DocumentId]) -> MResult<()> {
+        Ok(self.main.put::<_, Str, CowSlice<DocumentId>>(writer, SORTED_DOCUMENT_IDS_CACHE_KEY, documents_ids)?)
+    }
+
+    pub fn sorted_document_ids_cache(self, reader: &heed::RoTxn<MainT>) -> MResult<Option<Cow<[DocumentId]>>> {
+        Ok(self.main.get::<_, Str, CowSlice<DocumentId>>(reader, SORTED_DOCUMENT_IDS_CACHE_KEY)?)
+    }
+
     pub fn put_schema(self, writer: &mut heed::RwTxn<MainT>, schema: &Schema) -> MResult<()> {
         Ok(self.main.put::<_, Str, SerdeBincode<Schema>>(writer, SCHEMA_KEY, schema)?)
     }

meilisearch-core/src/update/documents_addition.rs

@@ -217,7 +217,7 @@ pub fn apply_addition<'a, 'b>(
     let mut indexer = RawIndexer::new(stop_words);
 
     // For each document in this update
-    for (document_id, document) in documents_additions {
+    for (document_id, document) in &documents_additions {
         // For each key-value pair in the document.
         for (attribute, value) in document {
             let field_id = schema.insert_and_index(&attribute)?;
@@ -229,7 +229,7 @@ pub fn apply_addition<'a, 'b>(
                 &mut indexer,
                 &schema,
                 field_id,
-                document_id,
+                *document_id,
                 &value,
             )?;
         }
@@ -257,6 +257,10 @@ pub fn apply_addition<'a, 'b>(
         index.facets.add(writer, facet_map)?;
     }
 
+    // update is finished; update sorted document id cache with new state
+    let mut document_ids = index.main.internal_docids(writer)?.to_vec();
+    super::cache_document_ids_sorted(writer, &ranked_map, index, &mut document_ids)?;
+
     Ok(())
 }
 
@@ -313,8 +317,8 @@ pub fn reindex_all_documents(writer: &mut heed::RwTxn<MainT>, index: &store::Ind
         index.facets.add(writer, facet_map)?;
     }
     // ^-- https://github.com/meilisearch/MeiliSearch/pull/631#issuecomment-626624470 --v
-    for document_id in documents_ids_to_reindex {
-        for result in index.documents_fields.document_fields(writer, document_id)? {
+    for document_id in &documents_ids_to_reindex {
+        for result in index.documents_fields.document_fields(writer, *document_id)? {
             let (field_id, bytes) = result?;
             let value: Value = serde_json::from_slice(bytes)?;
             ram_store.insert((document_id, field_id), value);
@@ -330,7 +334,7 @@ pub fn reindex_all_documents(writer: &mut heed::RwTxn<MainT>, index: &store::Ind
                 &mut indexer,
                 &schema,
                 field_id,
-                document_id,
+                *document_id,
                 &value,
             )?;
         }
@@ -354,6 +358,10 @@ pub fn reindex_all_documents(writer: &mut heed::RwTxn<MainT>, index: &store::Ind
         index.facets.add(writer, facet_map)?;
     }
 
+    // update is finished; update sorted document id cache with new state
+    let mut document_ids = index.main.internal_docids(writer)?.to_vec();
+    super::cache_document_ids_sorted(writer, &ranked_map, index, &mut document_ids)?;
+
     Ok(())
 }
 

meilisearch-core/src/update/documents_deletion.rs

@@ -8,7 +8,7 @@ use crate::database::{UpdateEvent, UpdateEventsEmitter};
 use crate::facets;
 use crate::store;
 use crate::update::{next_update_id, compute_short_prefixes, Update};
-use crate::{DocumentId, Error, MResult, RankedMap};
+use crate::{DocumentId, Error, MResult, RankedMap, MainWriter, Index};
 
 pub struct DocumentsDeletion {
     updates_store: store::Updates,
@@ -153,8 +153,8 @@ pub fn apply_documents_deletion(
     }
 
     let deleted_documents_len = deleted_documents.len() as u64;
-    for id in deleted_documents {
-        index.docs_words.del_doc_words(writer, id)?;
+    for id in &deleted_documents {
+        index.docs_words.del_doc_words(writer, *id)?;
     }
 
     let removed_words = fst::Set::from_iter(removed_words).unwrap();
@@ -180,5 +180,28 @@ pub fn apply_documents_deletion(
 
     compute_short_prefixes(writer, &words, index)?;
 
+    // update is finished; update sorted document id cache with new state
+    document_cache_remove_deleted(writer, index, &ranked_map, &deleted_documents)?;
+
+    Ok(())
+}
+
+/// rebuilds the document id cache by either removing deleted documents from the existing cache,
+/// and generating a new one from docs in store
+fn document_cache_remove_deleted(writer: &mut MainWriter, index: &Index, ranked_map: &RankedMap, documents_to_delete: &HashSet<DocumentId>) -> MResult<()> {
+    let new_cache = match index.main.sorted_document_ids_cache(writer)? {
+        // only keep documents that are not in the list of deleted documents. Order is preserved,
+        // no need to resort
+        Some(old_cache) => {
+            old_cache.iter().filter(|docid| !documents_to_delete.contains(docid)).cloned().collect::<Vec<_>>()
+        }
+        // couldn't find cached documents, try building a new cache from documents in store
+        None => {
+            let mut document_ids = index.main.internal_docids(writer)?.to_vec();
+            super::cache_document_ids_sorted(writer, ranked_map, index, &mut document_ids)?;
+            document_ids
+        }
+    };
+    index.main.put_sorted_document_ids_cache(writer, &new_cache)?;
     Ok(())
 }

meilisearch-core/src/update/mod.rs

@@ -25,8 +25,9 @@ use serde::{Deserialize, Serialize};
 use serde_json::Value;
 
 use meilisearch_error::ErrorCode;
+use meilisearch_types::DocumentId;
 
-use crate::{store, MResult};
+use crate::{store, MResult, RankedMap};
 use crate::database::{MainT, UpdateT};
 use crate::settings::SettingsUpdate;
 
@@ -371,3 +372,13 @@ where A: AsRef<[u8]>,
 
     Ok(())
 }
+
+fn cache_document_ids_sorted(
+    writer: &mut heed::RwTxn<MainT>,
+    ranked_map: &RankedMap,
+    index: &store::Index,
+    document_ids: &mut [DocumentId],
+) -> MResult<()> {
+    crate::bucket_sort::placeholder_document_sort(document_ids, index, writer, ranked_map)?;
+    index.main.put_sorted_document_ids_cache(writer, &document_ids)
+}

meilisearch-http/Cargo.toml

@@ -70,9 +70,9 @@ features = [
 optional = true
 
 [dev-dependencies]
+serde_url_params = "0.2.0"
 tempdir = "0.3.7"
 tokio = { version = "0.2.18", features = ["macros", "time"] }
-serde_url_params = "0.2.0"
 
 [dev-dependencies.assert-json-diff]
 git = "https://github.com/qdequele/assert-json-diff"

meilisearch-http/src/helpers/meilisearch.rs

@@ -20,11 +20,11 @@ use slice_group_by::GroupBy;
 use crate::error::{Error, ResponseError};
 
 pub trait IndexSearchExt {
-    fn new_search(&self, query: String) -> SearchBuilder;
+    fn new_search(&self, query: Option<String>) -> SearchBuilder;
 }
 
 impl IndexSearchExt for Index {
-    fn new_search(&self, query: String) -> SearchBuilder {
+    fn new_search(&self, query: Option<String>) -> SearchBuilder {
         SearchBuilder {
             index: self,
             query,
@@ -43,7 +43,7 @@ impl IndexSearchExt for Index {
 
 pub struct SearchBuilder<'a> {
     index: &'a Index,
-    query: String,
+    query: Option<String>,
     offset: usize,
     limit: usize,
     attributes_to_crop: Option<HashMap<String, usize>>,
@@ -156,7 +156,7 @@ impl<'a> SearchBuilder<'a> {
         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 result = query_builder.query(reader, self.query.as_deref(), self.offset..(self.offset + self.limit));
         let search_result = result.map_err(Error::search_documents)?;
         let time_ms = start.elapsed().as_millis() as usize;
 
@@ -245,7 +245,7 @@ impl<'a> SearchBuilder<'a> {
             nb_hits: search_result.nb_hits,
             exhaustive_nb_hits: search_result.exhaustive_nb_hit,
             processing_time_ms: time_ms,
-            query: self.query.to_string(),
+            query: self.query.unwrap_or_default(),
             facets_distribution: search_result.facets,
             exhaustive_facets_count: search_result.exhaustive_facets_count,
         };

meilisearch-http/src/routes/search.rs

@@ -24,7 +24,7 @@ pub fn services(cfg: &mut web::ServiceConfig) {
 #[derive(Serialize, Deserialize)]
 #[serde(rename_all = "camelCase", deny_unknown_fields)]
 pub struct SearchQuery {
-    q: String,
+    q: Option<String>,
     offset: Option<usize>,
     limit: Option<usize>,
     attributes_to_retrieve: Option<String>,
@@ -50,7 +50,7 @@ async fn search_with_url_query(
 #[derive(Deserialize)]
 #[serde(rename_all = "camelCase", deny_unknown_fields)]
 pub struct SearchQueryPost {
-    q: String,
+    q: Option<String>,
     offset: Option<usize>,
     limit: Option<usize>,
     attributes_to_retrieve: Option<Vec<String>>,
@@ -177,7 +177,6 @@ impl SearchQuery {
                     None => (),
                 }
             }
-
             search_builder.attributes_to_crop(final_attributes);
         }