Introduce the new Sort criterion and AscDesc enum

milli/src/criterion.rs

@@ -12,6 +12,9 @@ pub enum Criterion {
     Words,
     /// Sorted by increasing number of typos.
     Typo,
+    /// Dynamically sort at query time the documents. None, one or multiple Asc/Desc sortable
+    /// attributes can be used in place of this criterion at query time.
+    Sort,
     /// Sorted by increasing distance between matched query terms.
     Proximity,
     /// Documents with quey words contained in more important
@@ -38,26 +41,46 @@ impl Criterion {
 impl FromStr for Criterion {
     type Err = Error;
 
-    fn from_str(txt: &str) -> Result<Criterion, Self::Err> {
-        match txt {
+    fn from_str(text: &str) -> Result<Criterion, Self::Err> {
+        match text {
             "words" => Ok(Criterion::Words),
             "typo" => Ok(Criterion::Typo),
+            "sort" => Ok(Criterion::Sort),
             "proximity" => Ok(Criterion::Proximity),
             "attribute" => Ok(Criterion::Attribute),
             "exactness" => Ok(Criterion::Exactness),
-            text => match text.rsplit_once(':') {
-                Some((field_name, "asc")) => Ok(Criterion::Asc(field_name.to_string())),
-                Some((field_name, "desc")) => Ok(Criterion::Desc(field_name.to_string())),
-                _ => Err(UserError::InvalidCriterionName { name: text.to_string() }.into()),
+            text => match AscDesc::from_str(text) {
+                Ok(AscDesc::Asc(field)) => Ok(Criterion::Asc(field)),
+                Ok(AscDesc::Desc(field)) => Ok(Criterion::Desc(field)),
+                Err(error) => Err(error.into()),
             },
         }
     }
 }
 
+#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq)]
+pub enum AscDesc {
+    Asc(String),
+    Desc(String),
+}
+
+impl FromStr for AscDesc {
+    type Err = UserError;
+
+    fn from_str(text: &str) -> Result<AscDesc, Self::Err> {
+        match text.rsplit_once(':') {
+            Some((field_name, "asc")) => Ok(AscDesc::Asc(field_name.to_string())),
+            Some((field_name, "desc")) => Ok(AscDesc::Desc(field_name.to_string())),
+            _ => Err(UserError::InvalidCriterionName { name: text.to_string() }),
+        }
+    }
+}
+
 pub fn default_criteria() -> Vec<Criterion> {
     vec![
         Criterion::Words,
         Criterion::Typo,
+        Criterion::Sort,
         Criterion::Proximity,
         Criterion::Attribute,
         Criterion::Exactness,
@@ -71,6 +94,7 @@ impl fmt::Display for Criterion {
         match self {
             Words => f.write_str("words"),
             Typo => f.write_str("typo"),
+            Sort => f.write_str("sort"),
             Proximity => f.write_str("proximity"),
             Attribute => f.write_str("attribute"),
             Exactness => f.write_str("exactness"),

milli/src/search/criteria/mod.rs

@@ -1,5 +1,6 @@
 use std::borrow::Cow;
 use std::collections::HashMap;
+use std::str::FromStr;
 
 use roaring::RoaringBitmap;
 
@@ -273,8 +274,9 @@ impl<'t> CriteriaBuilder<'t> {
         query_tree: Option<Operation>,
         primitive_query: Option<Vec<PrimitiveQueryPart>>,
         filtered_candidates: Option<RoaringBitmap>,
+        sort_criteria: Option<Vec<String>>,
     ) -> Result<Final<'t>> {
-        use crate::criterion::Criterion as Name;
+        use crate::criterion::{AscDesc as AscDescName, Criterion as Name};
 
         let primitive_query = primitive_query.unwrap_or_default();
 
@@ -282,8 +284,30 @@ impl<'t> CriteriaBuilder<'t> {
             Box::new(Initial::new(query_tree, filtered_candidates)) as Box<dyn Criterion>;
         for name in self.index.criteria(&self.rtxn)? {
             criterion = match name {
-                Name::Typo => Box::new(Typo::new(self, criterion)),
                 Name::Words => Box::new(Words::new(self, criterion)),
+                Name::Typo => Box::new(Typo::new(self, criterion)),
+                Name::Sort => match sort_criteria {
+                    Some(ref sort_criteria) => {
+                        for text in sort_criteria {
+                            criterion = match AscDescName::from_str(text)? {
+                                AscDescName::Asc(field) => Box::new(AscDesc::asc(
+                                    &self.index,
+                                    &self.rtxn,
+                                    criterion,
+                                    field,
+                                )?),
+                                AscDescName::Desc(field) => Box::new(AscDesc::desc(
+                                    &self.index,
+                                    &self.rtxn,
+                                    criterion,
+                                    field,
+                                )?),
+                            };
+                        }
+                        criterion
+                    }
+                    None => criterion,
+                },
                 Name::Proximity => Box::new(Proximity::new(self, criterion)),
                 Name::Attribute => Box::new(Attribute::new(self, criterion)),
                 Name::Exactness => Box::new(Exactness::new(self, criterion, &primitive_query)?),

milli/src/search/mod.rs

@@ -135,7 +135,13 @@ impl<'a> Search<'a> {
         };
 
         let criteria_builder = criteria::CriteriaBuilder::new(self.rtxn, self.index)?;
-        let criteria = criteria_builder.build(query_tree, primitive_query, filtered_candidates)?;
+        let sort_criteria = None;
+        let criteria = criteria_builder.build(
+            query_tree,
+            primitive_query,
+            filtered_candidates,
+            sort_criteria,
+        )?;
 
         match self.index.distinct_field(self.rtxn)? {
             None => self.perform_sort(NoopDistinct, matching_words, criteria),

milli/tests/search/mod.rs

@@ -90,6 +90,7 @@ pub fn expected_order(
                     new_groups
                         .extend(group.linear_group_by_key(|d| d.proximity_rank).map(Vec::from));
                 }
+                Criterion::Sort => todo!("sort not supported right now"),
                 Criterion::Typo => {
                     group.sort_by_key(|d| d.typo_rank);
                     new_groups.extend(group.linear_group_by_key(|d| d.typo_rank).map(Vec::from));