Compute an exact count when using distinct

milli/src/search/criteria/initial.rs

@@ -3,32 +3,35 @@ use roaring::RoaringBitmap;
 use super::{Criterion, CriterionParameters, CriterionResult};
 use crate::search::criteria::{resolve_query_tree, Context};
 use crate::search::query_tree::Operation;
+use crate::search::Distinct;
 use crate::Result;
 
-pub struct Initial<'t> {
+pub struct Initial<'t, D> {
     ctx: &'t dyn Context<'t>,
     answer: Option<CriterionResult>,
     exhaustive_number_hits: bool,
+    distinct: Option<D>,
 }
 
-impl<'t> Initial<'t> {
+impl<'t, D> Initial<'t, D> {
     pub fn new(
         ctx: &'t dyn Context<'t>,
         query_tree: Option<Operation>,
         filtered_candidates: Option<RoaringBitmap>,
         exhaustive_number_hits: bool,
-    ) -> Initial {
+        distinct: Option<D>,
+    ) -> Initial<D> {
         let answer = CriterionResult {
             query_tree,
             candidates: None,
             filtered_candidates,
             bucket_candidates: None,
         };
-        Initial { ctx, answer: Some(answer), exhaustive_number_hits }
+        Initial { ctx, answer: Some(answer), exhaustive_number_hits, distinct }
     }
 }
 
-impl Criterion for Initial<'_> {
+impl<D: Distinct> Criterion for Initial<'_, D> {
     #[logging_timer::time("Initial::{}")]
     fn next(&mut self, params: &mut CriterionParameters) -> Result<Option<CriterionResult>> {
         self.answer
@@ -41,8 +44,20 @@ impl Criterion for Initial<'_> {
                         &mut params.wdcache,
                     )?;
 
-                    answer.candidates = Some(candidates.clone());
-                    answer.bucket_candidates = Some(candidates);
+                    let bucket_candidates = match &mut self.distinct {
+                        // may be really time consuming
+                        Some(distinct) => {
+                            let mut bucket_candidates = RoaringBitmap::new();
+                            for c in distinct.distinct(candidates.clone(), RoaringBitmap::new()) {
+                                bucket_candidates.insert(c?);
+                            }
+                            bucket_candidates
+                        }
+                        None => candidates.clone(),
+                    };
+
+                    answer.candidates = Some(candidates);
+                    answer.bucket_candidates = Some(bucket_candidates);
                 }
                 Ok(answer)
             })

milli/src/search/criteria/mod.rs

@@ -13,7 +13,7 @@ use self::typo::Typo;
 use self::words::Words;
 use super::query_tree::{Operation, PrimitiveQueryPart, Query, QueryKind};
 use crate::search::criteria::geo::Geo;
-use crate::search::{word_derivations, WordDerivationsCache};
+use crate::search::{word_derivations, Distinct, WordDerivationsCache};
 use crate::{AscDesc as AscDescName, DocumentId, FieldId, Index, Member, Result};
 
 mod asc_desc;
@@ -226,21 +226,26 @@ impl<'t> CriteriaBuilder<'t> {
         Ok(Self { rtxn, index, words_fst, words_prefixes_fst })
     }
 
-    pub fn build(
+    pub fn build<D: 't + Distinct>(
         &'t self,
         query_tree: Option<Operation>,
         primitive_query: Option<Vec<PrimitiveQueryPart>>,
         filtered_candidates: Option<RoaringBitmap>,
         sort_criteria: Option<Vec<AscDescName>>,
         exhaustive_number_hits: bool,
+        distinct: Option<D>,
     ) -> Result<Final<'t>> {
         use crate::criterion::Criterion as Name;
 
         let primitive_query = primitive_query.unwrap_or_default();
 
-        let mut criterion =
-            Box::new(Initial::new(self, query_tree, filtered_candidates, exhaustive_number_hits))
-                as Box<dyn Criterion>;
+        let mut criterion = Box::new(Initial::new(
+            self,
+            query_tree,
+            filtered_candidates,
+            exhaustive_number_hits,
+            distinct,
+        )) as Box<dyn Criterion>;
         for name in self.index.criteria(&self.rtxn)? {
             criterion = match name {
                 Name::Words => Box::new(Words::new(self, criterion)),

milli/src/search/criteria/typo.rs

@@ -348,6 +348,7 @@ mod test {
     use super::super::initial::Initial;
     use super::super::test::TestContext;
     use super::*;
+    use crate::search::NoopDistinct;
 
     fn display_criteria(mut criteria: Typo, mut parameters: CriterionParameters) -> String {
         let mut result = String::new();
@@ -368,7 +369,8 @@ mod test {
             excluded_candidates: &RoaringBitmap::new(),
         };
 
-        let parent = Initial::new(&context, query_tree, facet_candidates, false);
+        let parent =
+            Initial::<NoopDistinct>::new(&context, query_tree, facet_candidates, false, None);
         let criteria = Typo::new(&context, Box::new(parent));
 
         let result = display_criteria(criteria, criterion_parameters);
@@ -405,7 +407,8 @@ mod test {
             wdcache: &mut WordDerivationsCache::new(),
             excluded_candidates: &RoaringBitmap::new(),
         };
-        let parent = Initial::new(&context, Some(query_tree), facet_candidates, false);
+        let parent =
+            Initial::<NoopDistinct>::new(&context, Some(query_tree), facet_candidates, false, None);
         let criteria = Typo::new(&context, Box::new(parent));
 
         let result = display_criteria(criteria, criterion_parameters);
@@ -439,7 +442,13 @@ mod test {
             wdcache: &mut WordDerivationsCache::new(),
             excluded_candidates: &RoaringBitmap::new(),
         };
-        let parent = Initial::new(&context, query_tree, Some(facet_candidates.clone()), false);
+        let parent = Initial::<NoopDistinct>::new(
+            &context,
+            query_tree,
+            Some(facet_candidates.clone()),
+            false,
+            None,
+        );
         let criteria = Typo::new(&context, Box::new(parent));
 
         let result = display_criteria(criteria, criterion_parameters);
@@ -476,8 +485,13 @@ mod test {
             wdcache: &mut WordDerivationsCache::new(),
             excluded_candidates: &RoaringBitmap::new(),
         };
-        let parent =
-            Initial::new(&context, Some(query_tree), Some(facet_candidates.clone()), false);
+        let parent = Initial::<NoopDistinct>::new(
+            &context,
+            Some(query_tree),
+            Some(facet_candidates.clone()),
+            false,
+            None,
+        );
         let criteria = Typo::new(&context, Box::new(parent));
 
         let result = display_criteria(criteria, criterion_parameters);

milli/src/search/distinct/facet_distinct.rs

@@ -21,6 +21,7 @@ const DOCID_SIZE: usize = size_of::<DocumentId>();
 /// care to keep the document we are currently on, and remove it from the excluded list. The next
 /// iterations will never contain any occurence of a document with the same distinct value as a
 /// document from previous iterations.
+#[derive(Clone)]
 pub struct FacetDistinct<'a> {
     distinct: FieldId,
     index: &'a Index,

milli/src/search/mod.rs

@@ -191,21 +191,33 @@ impl<'a> Search<'a> {
         }
 
         let criteria_builder = criteria::CriteriaBuilder::new(self.rtxn, self.index)?;
+
+        match self.index.distinct_field(self.rtxn)? {
+            None => {
+                let criteria = criteria_builder.build::<NoopDistinct>(
+                    query_tree,
+                    primitive_query,
+                    filtered_candidates,
+                    self.sort_criteria.clone(),
+                    self.exhaustive_number_hits,
+                    None,
+                )?;
+                self.perform_sort(NoopDistinct, matching_words.unwrap_or_default(), criteria)
+            }
+            Some(name) => {
+                let field_ids_map = self.index.fields_ids_map(self.rtxn)?;
+                match field_ids_map.id(name) {
+                    Some(fid) => {
+                        let distinct = FacetDistinct::new(fid, self.index, self.rtxn);
+
                         let criteria = criteria_builder.build(
                             query_tree,
                             primitive_query,
                             filtered_candidates,
                             self.sort_criteria.clone(),
                             self.exhaustive_number_hits,
+                            Some(distinct.clone()),
                         )?;
-
-        match self.index.distinct_field(self.rtxn)? {
-            None => self.perform_sort(NoopDistinct, matching_words.unwrap_or_default(), criteria),
-            Some(name) => {
-                let field_ids_map = self.index.fields_ids_map(self.rtxn)?;
-                match field_ids_map.id(name) {
-                    Some(fid) => {
-                        let distinct = FacetDistinct::new(fid, self.index, self.rtxn);
                         self.perform_sort(distinct, matching_words.unwrap_or_default(), criteria)
                     }
                     None => Ok(SearchResult::default()),