Introduce the sort ranking rule working with the new search structures

milli/src/search/new/sort.rs

@@ -0,0 +1,118 @@
+use heed::RoTxn;
+use roaring::RoaringBitmap;
+
+use super::{
+    db_cache::DatabaseCache, RankingRule, RankingRuleOutput, RankingRuleOutputIter,
+    RankingRuleOutputIterWrapper, RankingRuleQueryTrait,
+};
+use crate::{
+    // facet::FacetType,
+    heed_codec::{facet::FacetGroupKeyCodec, ByteSliceRefCodec},
+    search::facet::{ascending_facet_sort, descending_facet_sort},
+    FieldId,
+    Index,
+    Result,
+};
+
+// TODO: The implementation of Sort is not correct:
+// (1) it should not return documents it has already returned (does the current implementation have the same bug?)
+// (2) at the end, it should return all the remaining documents (this could be ensured at the trait level?)
+
+pub struct Sort<'transaction, Query> {
+    field_id: Option<FieldId>,
+    is_ascending: bool,
+    iter: Option<RankingRuleOutputIterWrapper<'transaction, Query>>,
+}
+impl<'transaction, Query> Sort<'transaction, Query> {
+    pub fn new(
+        index: &'transaction Index,
+        rtxn: &'transaction heed::RoTxn,
+        field_name: String,
+        is_ascending: bool,
+    ) -> Result<Self> {
+        let fields_ids_map = index.fields_ids_map(rtxn)?;
+        let field_id = fields_ids_map.id(&field_name);
+
+        // TODO: What is this, why?
+        // let faceted_candidates = match field_id {
+        //     Some(field_id) => {
+        //         let number_faceted =
+        //             index.faceted_documents_ids(rtxn, field_id, FacetType::Number)?;
+        //         let string_faceted =
+        //             index.faceted_documents_ids(rtxn, field_id, FacetType::String)?;
+        //         number_faceted | string_faceted
+        //     }
+        //     None => RoaringBitmap::default(),
+        // };
+
+        Ok(Self { field_id, is_ascending, iter: None })
+    }
+}
+
+impl<'transaction, Query: RankingRuleQueryTrait> RankingRule<'transaction, Query>
+    for Sort<'transaction, Query>
+{
+    fn start_iteration(
+        &mut self,
+        index: &Index,
+        txn: &'transaction RoTxn,
+        _db_cache: &mut DatabaseCache<'transaction>,
+        parent_candidates: &RoaringBitmap,
+        parent_query_graph: &Query,
+    ) -> Result<()> {
+        let iter: RankingRuleOutputIterWrapper<Query> = match self.field_id {
+            Some(field_id) => {
+                let make_iter =
+                    if self.is_ascending { ascending_facet_sort } else { descending_facet_sort };
+
+                let number_iter = make_iter(
+                    txn,
+                    index
+                        .facet_id_f64_docids
+                        .remap_key_type::<FacetGroupKeyCodec<ByteSliceRefCodec>>(),
+                    field_id,
+                    parent_candidates.clone(),
+                )?;
+
+                let string_iter = make_iter(
+                    txn,
+                    index
+                        .facet_id_string_docids
+                        .remap_key_type::<FacetGroupKeyCodec<ByteSliceRefCodec>>(),
+                    field_id,
+                    parent_candidates.clone(),
+                )?;
+                let query_graph = parent_query_graph.clone();
+                RankingRuleOutputIterWrapper::new(Box::new(number_iter.chain(string_iter).map(
+                    move |docids| {
+                        Ok(RankingRuleOutput { query: query_graph.clone(), candidates: docids? })
+                    },
+                )))
+            }
+            None => RankingRuleOutputIterWrapper::new(Box::new(std::iter::empty())),
+        };
+        self.iter = Some(iter);
+        Ok(())
+    }
+
+    fn next_bucket(
+        &mut self,
+        _index: &Index,
+        _txn: &'transaction RoTxn,
+        _db_cache: &mut DatabaseCache<'transaction>,
+        _universe: &RoaringBitmap,
+    ) -> Result<Option<RankingRuleOutput<Query>>> {
+        let iter = self.iter.as_mut().unwrap();
+        // TODO: we should make use of the universe in the function below
+        iter.next_bucket()
+    }
+
+    fn end_iteration(
+        &mut self,
+        _index: &Index,
+        _txn: &'transaction RoTxn,
+        _db_cache: &mut DatabaseCache<'transaction>,
+    ) {
+        self.iter = None;
+    }
+}