feat(index): store fields distribution in index

milli/src/update/index_documents/mod.rs

@@ -358,6 +358,7 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
         let TransformOutput {
             primary_key,
             fields_ids_map,
+            fields_distribution,
             external_documents_ids,
             new_documents_ids,
             replaced_documents_ids,
@@ -551,6 +552,9 @@ impl<'t, 'u, 'i, 'a> IndexDocuments<'t, 'u, 'i, 'a> {
         // We write the fields ids map into the main database
         self.index.put_fields_ids_map(self.wtxn, &fields_ids_map)?;
 
+        // We write the fields distribution into the main database
+        self.index.put_fields_distribution(self.wtxn, &fields_distribution)?;
+
         // We write the primary key field id into the main database
         self.index.put_primary_key(self.wtxn, &primary_key)?;
 

milli/src/update/index_documents/transform.rs

@@ -14,12 +14,14 @@ use crate::{Index, BEU32, MergeFn, FieldsIdsMap, ExternalDocumentsIds, FieldId};
 use crate::update::{AvailableDocumentsIds, UpdateIndexingStep};
 use super::merge_function::merge_two_obkvs;
 use super::{create_writer, create_sorter, IndexDocumentsMethod};
+use crate::index::FieldsDistribution;
 
 const DEFAULT_PRIMARY_KEY_NAME: &str = "id";
 
 pub struct TransformOutput {
     pub primary_key: String,
     pub fields_ids_map: FieldsIdsMap,
+    pub fields_distribution: FieldsDistribution,
     pub external_documents_ids: ExternalDocumentsIds<'static>,
     pub new_documents_ids: RoaringBitmap,
     pub replaced_documents_ids: RoaringBitmap,
@@ -74,6 +76,7 @@ impl Transform<'_, '_> {
         F: Fn(UpdateIndexingStep) + Sync,
     {
         let mut fields_ids_map = self.index.fields_ids_map(self.rtxn)?;
+        let mut fields_distribution = self.index.fields_distribution(self.rtxn)?;
         let external_documents_ids = self.index.external_documents_ids(self.rtxn).unwrap();
 
         // Deserialize the whole batch of documents in memory.
@@ -103,6 +106,7 @@ impl Transform<'_, '_> {
             return Ok(TransformOutput {
                 primary_key,
                 fields_ids_map,
+                fields_distribution,
                 external_documents_ids: ExternalDocumentsIds::default(),
                 new_documents_ids: RoaringBitmap::new(),
                 replaced_documents_ids: RoaringBitmap::new(),
@@ -148,6 +152,8 @@ impl Transform<'_, '_> {
             // We prepare the fields ids map with the documents keys.
             for (key, _value) in &document {
                 fields_ids_map.insert(&key).context("field id limit reached")?;
+
+                *fields_distribution.entry(key.to_owned()).or_default() += 1;
             }
 
             // We retrieve the user id from the document based on the primary key name,
@@ -200,6 +206,7 @@ impl Transform<'_, '_> {
             sorter,
             primary_key,
             fields_ids_map,
+            fields_distribution,
             documents_count,
             external_documents_ids,
             progress_callback,
@@ -212,6 +219,7 @@ impl Transform<'_, '_> {
         F: Fn(UpdateIndexingStep) + Sync,
     {
         let mut fields_ids_map = self.index.fields_ids_map(self.rtxn)?;
+        let mut fields_distribution = self.index.fields_distribution(self.rtxn)?;
         let external_documents_ids = self.index.external_documents_ids(self.rtxn).unwrap();
 
         let mut csv = csv::Reader::from_reader(reader);
@@ -307,6 +315,10 @@ impl Transform<'_, '_> {
                 json_buffer.clear();
                 serde_json::to_writer(&mut json_buffer, &field)?;
                 writer.insert(*field_id, &json_buffer)?;
+
+                let field_name = fields_ids_map.name(*field_id).unwrap();
+
+                *fields_distribution.entry(field_name.to_string()).or_default() += 1;
             }
 
             // We use the extracted/generated user id as the key for this document.
@@ -328,6 +340,7 @@ impl Transform<'_, '_> {
             sorter,
             primary_key_name,
             fields_ids_map,
+            fields_distribution,
             documents_count,
             external_documents_ids,
             progress_callback,
@@ -342,6 +355,7 @@ impl Transform<'_, '_> {
         sorter: grenad::Sorter<MergeFn>,
         primary_key: String,
         fields_ids_map: FieldsIdsMap,
+        fields_distribution: FieldsDistribution,
         approximate_number_of_documents: usize,
         mut external_documents_ids: ExternalDocumentsIds<'_>,
         progress_callback: F,
@@ -439,6 +453,7 @@ impl Transform<'_, '_> {
         Ok(TransformOutput {
             primary_key,
             fields_ids_map,
+            fields_distribution,
             external_documents_ids: external_documents_ids.into_static(),
             new_documents_ids,
             replaced_documents_ids,
@@ -457,6 +472,7 @@ impl Transform<'_, '_> {
         new_fields_ids_map: FieldsIdsMap,
     ) -> anyhow::Result<TransformOutput>
     {
+        let fields_distribution = self.index.fields_distribution(self.rtxn)?;
         let external_documents_ids = self.index.external_documents_ids(self.rtxn)?;
         let documents_ids = self.index.documents_ids(self.rtxn)?;
         let documents_count = documents_ids.len() as usize;
@@ -492,6 +508,7 @@ impl Transform<'_, '_> {
         Ok(TransformOutput {
             primary_key,
             fields_ids_map: new_fields_ids_map,
+            fields_distribution,
             external_documents_ids: external_documents_ids.into_static(),
             new_documents_ids: documents_ids,
             replaced_documents_ids: RoaringBitmap::default(),

milli/src/update/settings.rs

@@ -183,7 +183,7 @@ impl<'a, 't, 'u, 'i> Settings<'a, 't, 'u, 'i> {
         Ok(true)
     }
 
-    /// Udpates the index's searchable attributes. This causes the field map to be recomputed to
+    /// Updates the index's searchable attributes. This causes the field map to be recomputed to
     /// reflect the order of the searchable attributes.
     fn update_searchable(&mut self) -> anyhow::Result<bool> {
         match self.searchable_fields {