Add settings to force milli to exhaustively compute the total number of hits

milli/src/search/criteria/initial.rs

@@ -1,17 +1,22 @@
 use roaring::RoaringBitmap;
 
 use super::{Criterion, CriterionParameters, CriterionResult};
+use crate::search::criteria::{resolve_query_tree, Context};
 use crate::search::query_tree::Operation;
 use crate::Result;
 
-pub struct Initial {
+pub struct Initial<'t> {
+    ctx: &'t dyn Context<'t>,
     answer: Option<CriterionResult>,
+    exhaustive_number_hits: bool,
 }
 
-impl Initial {
+impl<'t> Initial<'t> {
     pub fn new(
+        ctx: &'t dyn Context<'t>,
         query_tree: Option<Operation>,
         filtered_candidates: Option<RoaringBitmap>,
+        exhaustive_number_hits: bool,
     ) -> Initial {
         let answer = CriterionResult {
             query_tree,
@@ -19,13 +24,28 @@ impl Initial {
             filtered_candidates,
             bucket_candidates: None,
         };
-        Initial { answer: Some(answer) }
+        Initial { ctx, answer: Some(answer), exhaustive_number_hits }
     }
 }
 
-impl Criterion for Initial {
+impl Criterion for Initial<'_> {
     #[logging_timer::time("Initial::{}")]
-    fn next(&mut self, _: &mut CriterionParameters) -> Result<Option<CriterionResult>> {
+    fn next(&mut self, params: &mut CriterionParameters) -> Result<Option<CriterionResult>> {
-        Ok(self.answer.take())
+        self.answer
+            .take()
+            .map(|mut answer| {
+                if self.exhaustive_number_hits && answer.query_tree.is_some() {
+                    let candidates = resolve_query_tree(
+                        self.ctx,
+                        answer.query_tree.as_ref().unwrap(),
+                        &mut params.wdcache,
+                    )?;
+
+                    answer.candidates = Some(candidates.clone());
+                    answer.bucket_candidates = Some(candidates);
+                }
+                Ok(answer)
+            })
+            .transpose()
     }
 }

milli/src/search/criteria/mod.rs

@@ -232,13 +232,15 @@ impl<'t> CriteriaBuilder<'t> {
         primitive_query: Option<Vec<PrimitiveQueryPart>>,
         filtered_candidates: Option<RoaringBitmap>,
         sort_criteria: Option<Vec<AscDescName>>,
+        exhaustive_number_hits: bool,
     ) -> Result<Final<'t>> {
         use crate::criterion::Criterion as Name;
 
         let primitive_query = primitive_query.unwrap_or_default();
 
         let mut criterion =
-            Box::new(Initial::new(query_tree, filtered_candidates)) as Box<dyn Criterion>;
+            Box::new(Initial::new(self, query_tree, filtered_candidates, exhaustive_number_hits))
+                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

@@ -368,7 +368,7 @@ mod test {
             excluded_candidates: &RoaringBitmap::new(),
         };
 
-        let parent = Initial::new(query_tree, facet_candidates);
+        let parent = Initial::new(&context, query_tree, facet_candidates, false);
         let criteria = Typo::new(&context, Box::new(parent));
 
         let result = display_criteria(criteria, criterion_parameters);
@@ -405,7 +405,7 @@ mod test {
             wdcache: &mut WordDerivationsCache::new(),
             excluded_candidates: &RoaringBitmap::new(),
         };
-        let parent = Initial::new(Some(query_tree), facet_candidates);
+        let parent = Initial::new(&context, Some(query_tree), facet_candidates, false);
         let criteria = Typo::new(&context, Box::new(parent));
 
         let result = display_criteria(criteria, criterion_parameters);
@@ -439,7 +439,7 @@ mod test {
             wdcache: &mut WordDerivationsCache::new(),
             excluded_candidates: &RoaringBitmap::new(),
         };
-        let parent = Initial::new(query_tree, Some(facet_candidates.clone()));
+        let parent = Initial::new(&context, query_tree, Some(facet_candidates.clone()), false);
         let criteria = Typo::new(&context, Box::new(parent));
 
         let result = display_criteria(criteria, criterion_parameters);
@@ -476,7 +476,8 @@ mod test {
             wdcache: &mut WordDerivationsCache::new(),
             excluded_candidates: &RoaringBitmap::new(),
         };
-        let parent = Initial::new(Some(query_tree), Some(facet_candidates.clone()));
+        let parent =
+            Initial::new(&context, Some(query_tree), Some(facet_candidates.clone()), false);
         let criteria = Typo::new(&context, Box::new(parent));
 
         let result = display_criteria(criteria, criterion_parameters);

milli/src/search/mod.rs

@@ -47,6 +47,7 @@ pub struct Search<'a> {
     terms_matching_strategy: TermsMatchingStrategy,
     authorize_typos: bool,
     words_limit: usize,
+    exhaustive_number_hits: bool,
     rtxn: &'a heed::RoTxn<'a>,
     index: &'a Index,
 }
@@ -61,6 +62,7 @@ impl<'a> Search<'a> {
             sort_criteria: None,
             terms_matching_strategy: TermsMatchingStrategy::default(),
             authorize_typos: true,
+            exhaustive_number_hits: false,
             words_limit: 10,
             rtxn,
             index,
@@ -107,6 +109,11 @@ impl<'a> Search<'a> {
         self
     }
 
+    pub fn exhaustive_number_hits(&mut self, exhaustive_number_hits: bool) -> &mut Search<'a> {
+        self.exhaustive_number_hits = exhaustive_number_hits;
+        self
+    }
+
     fn is_typo_authorized(&self) -> Result<bool> {
         let index_authorizes_typos = self.index.authorize_typos(self.rtxn)?;
         // only authorize typos if both the index and the query allow it.
@@ -189,6 +196,7 @@ impl<'a> Search<'a> {
             primitive_query,
             filtered_candidates,
             self.sort_criteria.clone(),
+            self.exhaustive_number_hits,
         )?;
 
         match self.index.distinct_field(self.rtxn)? {
@@ -262,6 +270,7 @@ impl fmt::Debug for Search<'_> {
             terms_matching_strategy,
             authorize_typos,
             words_limit,
+            exhaustive_number_hits,
             rtxn: _,
             index: _,
         } = self;
@@ -273,6 +282,7 @@ impl fmt::Debug for Search<'_> {
             .field("sort_criteria", sort_criteria)
             .field("terms_matching_strategy", terms_matching_strategy)
             .field("authorize_typos", authorize_typos)
+            .field("exhaustive_number_hits", exhaustive_number_hits)
             .field("words_limit", words_limit)
             .finish()
     }

milli/tests/search/query_criteria.rs

@@ -51,7 +51,7 @@ macro_rules! test_criterion {
     };
 }
 
-test_criterion!(none_allow_typo, ALLOW_OPTIONAL_WORDS, ALLOW_TYPOS, vec![], vec![]);
+test_criterion!(none_allow_typo, DISALLOW_OPTIONAL_WORDS, ALLOW_TYPOS, vec![], vec![]);
 test_criterion!(none_disallow_typo, DISALLOW_OPTIONAL_WORDS, DISALLOW_TYPOS, vec![], vec![]);
 test_criterion!(words_allow_typo, ALLOW_OPTIONAL_WORDS, ALLOW_TYPOS, vec![Words], vec![]);
 test_criterion!(