Introduce a structure to implement ranking rules with graph algorithms

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

@@ -0,0 +1,43 @@
+use std::collections::{BTreeSet, HashMap, HashSet};
+
+use heed::RoTxn;
+
+use super::{Edge, RankingRuleGraph, RankingRuleGraphTrait};
+use crate::new::db_cache::DatabaseCache;
+use crate::new::QueryGraph;
+use crate::{Index, Result};
+
+impl<G: RankingRuleGraphTrait> RankingRuleGraph<G> {
+    pub fn build<'db_cache, 'transaction: 'db_cache>(
+        index: &Index,
+        txn: &'transaction RoTxn,
+        db_cache: &mut DatabaseCache<'transaction>,
+        query_graph: QueryGraph,
+    ) -> Result<Self> {
+        let mut ranking_rule_graph = Self { query_graph, all_edges: vec![], node_edges: vec![] };
+
+        for (node_idx, node) in ranking_rule_graph.query_graph.nodes.iter().enumerate() {
+            ranking_rule_graph.node_edges.push(BTreeSet::new());
+            let new_edges = ranking_rule_graph.node_edges.last_mut().unwrap();
+
+            let Some(from_node_data) = G::build_visit_from_node(index, txn, db_cache, node)? else { continue };
+
+            for &successor_idx in ranking_rule_graph.query_graph.edges[node_idx].outgoing.iter() {
+                let to_node = &ranking_rule_graph.query_graph.nodes[successor_idx];
+                let Some(edges) = G::build_visit_to_node(index, txn, db_cache, to_node, &from_node_data)? else { continue };
+                for (cost, details) in edges {
+                    ranking_rule_graph.all_edges.push(Some(Edge {
+                        from_node: node_idx,
+                        to_node: successor_idx,
+                        cost,
+                        details,
+                    }));
+                    new_edges.insert(ranking_rule_graph.all_edges.len() - 1);
+                }
+            }
+        }
+        ranking_rule_graph.simplify();
+
+        Ok(ranking_rule_graph)
+    }
+}