Add exactness ranking rules

milli/src/search/new/ranking_rule_graph/exactness/mod.rs

@@ -0,0 +1,107 @@
+use roaring::RoaringBitmap;
+
+use super::{ComputedCondition, DeadEndsCache, RankingRuleGraph, RankingRuleGraphTrait};
+use crate::search::new::interner::{DedupInterner, Interned, MappedInterner};
+use crate::search::new::query_graph::{QueryGraph, QueryNode};
+use crate::search::new::query_term::{ExactTerm, LocatedQueryTermSubset};
+use crate::{CboRoaringBitmapCodec, Result, SearchContext, SearchLogger};
+
+/// - Exactness as first ranking rule: TermsMatchingStrategy? prefer a document that matches 1 word exactly and no other
+/// word than a doc that matches 9 words non exactly but none exactly
+/// - `TermsMatchingStrategy` as a word + exactness optimization: we could consider
+///
+/// "naive vision"
+/// condition from one node to another:
+/// - word exactly present: cost 0
+/// - word typo/ngram/prefix/missing: cost 1, not remove from query graph, edge btwn the two nodes, return the universe without condition when resolving, destination query term is inside
+///
+/// Three strategies:
+/// 1. ExactAttribute: word position / word_fid_docid
+/// 2. AttributeStart:
+/// 3. AttributeContainsExact => implementable via `RankingRuleGraphTrait`
+
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub enum ExactnessCondition {
+    ExactInAttribute(LocatedQueryTermSubset),
+    Skip(LocatedQueryTermSubset),
+}
+
+pub enum ExactnessGraph {}
+
+fn compute_docids(
+    ctx: &mut SearchContext,
+    dest_node: &LocatedQueryTermSubset,
+    universe: &RoaringBitmap,
+) -> Result<RoaringBitmap> {
+    let exact_term = if let Some(exact_term) = dest_node.term_subset.exact_term(ctx) {
+        exact_term
+    } else {
+        return Ok(Default::default());
+    };
+    let mut candidates = match exact_term {
+        ExactTerm::Phrase(phrase) => ctx.get_phrase_docids(phrase)?.clone(),
+        ExactTerm::Word(word) => {
+            if let Some(word_candidates) = ctx.get_db_word_docids(word)? {
+                CboRoaringBitmapCodec::deserialize_from(word_candidates)?
+            } else {
+                return Ok(Default::default());
+            }
+        }
+    };
+    // TODO: synonyms?
+    candidates &= universe;
+    Ok(candidates)
+}
+
+impl RankingRuleGraphTrait for ExactnessGraph {
+    type Condition = ExactnessCondition;
+
+    fn resolve_condition(
+        ctx: &mut SearchContext,
+        condition: &Self::Condition,
+        universe: &RoaringBitmap,
+    ) -> Result<ComputedCondition> {
+        let (docids, dest_node) = match condition {
+            ExactnessCondition::ExactInAttribute(dest_node) => {
+                (compute_docids(ctx, dest_node, universe)?, dest_node)
+            }
+            ExactnessCondition::Skip(dest_node) => (universe.clone(), dest_node),
+        };
+        Ok(ComputedCondition {
+            docids,
+            universe_len: universe.len(),
+            start_term_subset: None,
+            end_term_subset: dest_node.clone(),
+        })
+    }
+
+    fn build_edges(
+        _ctx: &mut SearchContext,
+        conditions_interner: &mut DedupInterner<Self::Condition>,
+        _source_node: Option<&LocatedQueryTermSubset>,
+        dest_node: &LocatedQueryTermSubset,
+    ) -> Result<Vec<(u32, Interned<Self::Condition>)>> {
+        let exact_condition = ExactnessCondition::ExactInAttribute(dest_node.clone());
+        let exact_condition = conditions_interner.insert(exact_condition);
+
+        let skip_condition = ExactnessCondition::Skip(dest_node.clone());
+        let skip_condition = conditions_interner.insert(skip_condition);
+        Ok(vec![(0, exact_condition), (1, skip_condition)])
+    }
+
+    fn log_state(
+        graph: &RankingRuleGraph<Self>,
+        paths: &[Vec<Interned<Self::Condition>>],
+        dead_ends_cache: &DeadEndsCache<Self::Condition>,
+        universe: &RoaringBitmap,
+        costs: &MappedInterner<QueryNode, Vec<u64>>,
+        cost: u64,
+        logger: &mut dyn SearchLogger<QueryGraph>,
+    ) {
+        todo!()
+    }
+
+    fn label_for_condition(ctx: &mut SearchContext, condition: &Self::Condition) -> Result<String> {
+        todo!()
+    }
+}

milli/src/search/new/ranking_rule_graph/mod.rs

@@ -10,6 +10,8 @@ mod cheapest_paths;
 mod condition_docids_cache;
 mod dead_ends_cache;
 
+/// Implementation of the `exactness` ranking rule
+mod exactness;
 /// Implementation of the `proximity` ranking rule
 mod proximity;
 /// Implementation of the `typo` ranking rule
@@ -20,6 +22,7 @@ use std::hash::Hash;
 pub use cheapest_paths::PathVisitor;
 pub use condition_docids_cache::ConditionDocIdsCache;
 pub use dead_ends_cache::DeadEndsCache;
+pub use exactness::{ExactnessCondition, ExactnessGraph};
 pub use proximity::{ProximityCondition, ProximityGraph};
 use roaring::RoaringBitmap;
 pub use typo::{TypoCondition, TypoGraph};