extract exact word docids

milli/src/index.rs

@@ -964,6 +964,11 @@ impl Index {
             .get::<_, Str, SerdeBincode<Vec<&str>>>(txn, main_key::EXACT_ATTRIBUTES)?
             .unwrap_or_default())
     }
+    pub fn exact_attributes_ids(&self, txn: &RoTxn) -> Result<HashSet<FieldId>> {
+        let attrs = self.exact_attributes(txn)?;
+        let fid_map = self.fields_ids_map(txn)?;
+        Ok(attrs.iter().filter_map(|attr| fid_map.id(attr)).collect())
+    }
 
     pub(crate) fn put_exact_attributes(&self, txn: &mut RwTxn, attrs: &[&str]) -> Result<()> {
         self.main.put::<_, Str, SerdeBincode<&[&str]>>(txn, main_key::EXACT_ATTRIBUTES, &attrs)?;

milli/src/lib.rs

@@ -74,6 +74,10 @@ pub fn absolute_from_relative_position(field_id: FieldId, relative: RelativePosi
     (field_id as u32) << 16 | (relative as u32)
 }
 
+pub fn field_id_from_position(position: u32) -> FieldId {
+    (position >> 16 & 0xffff) as u16
+}
+
 /// Transform a raw obkv store into a JSON Object.
 pub fn obkv_to_json(
     displayed_fields: &[FieldId],

milli/src/update/index_documents/extract/extract_word_docids.rs

@@ -1,3 +1,4 @@
+use std::collections::HashSet;
 use std::fs::File;
 use std::io;
 use std::iter::FromIterator;
@@ -10,8 +11,8 @@ use super::helpers::{
 };
 use crate::error::SerializationError;
 use crate::index::db_name::DOCID_WORD_POSITIONS;
-use crate::update::index_documents::MergeFn;
+use crate::update::index_documents::helpers::read_u32_ne_bytes;
-use crate::Result;
+use crate::{field_id_from_position, FieldId, Result};
 
 /// Extracts the word and the documents ids where this word appear.
 ///
@@ -24,6 +25,7 @@ use crate::Result;
 pub fn extract_word_docids<R: io::Read + io::Seek>(
     docid_word_positions: grenad::Reader<R>,
     indexer: GrenadParameters,
+    exact_attributes: &HashSet<FieldId>,
 ) -> Result<(grenad::Reader<File>, grenad::Reader<File>)> {
     let max_memory = indexer.max_memory_by_thread();
 
@@ -35,21 +37,50 @@ pub fn extract_word_docids<R: io::Read + io::Seek>(
         max_memory,
     );
 
+    let mut exact_word_docids_sorter = create_sorter(
+        merge_roaring_bitmaps,
+        indexer.chunk_compression_type,
+        indexer.chunk_compression_level,
+        indexer.max_nb_chunks,
+        max_memory,
+    );
+
     let mut value_buffer = Vec::new();
     let mut cursor = docid_word_positions.into_cursor()?;
-    while let Some((key, _value)) = cursor.move_on_next()? {
+    while let Some((key, positions)) = cursor.move_on_next()? {
         let (document_id_bytes, word_bytes) = try_split_array_at(key)
             .ok_or_else(|| SerializationError::Decoding { db_name: Some(DOCID_WORD_POSITIONS) })?;
         let document_id = u32::from_be_bytes(document_id_bytes);
 
         let bitmap = RoaringBitmap::from_iter(Some(document_id));
         serialize_roaring_bitmap(&bitmap, &mut value_buffer)?;
-        word_docids_sorter.insert(word_bytes, &value_buffer)?;
+
+        // If there are no exact attributes, we do not need to iterate over positions.
+        if exact_attributes.is_empty() {
+            word_docids_sorter.insert(word_bytes, &value_buffer)?;
+        } else {
+            let mut added_to_exact = false;
+            let mut added_to_word_docids = false;
+            for position in read_u32_ne_bytes(positions) {
+                // as soon as we know that this word had been to both readers, we don't need to
+                // iterate over the positions.
+                if added_to_exact && added_to_word_docids {
+                    break;
+                }
+                let fid = field_id_from_position(position);
+                if exact_attributes.contains(&fid) && !added_to_exact {
+                    exact_word_docids_sorter.insert(word_bytes, &value_buffer)?;
+                    added_to_exact = true;
+                } else if !added_to_word_docids {
+                    word_docids_sorter.insert(word_bytes, &value_buffer)?;
+                    added_to_word_docids = true;
+                }
+            }
+        }
     }
 
-    let empty_sorter = grenad::Sorter::new(merge_roaring_bitmaps as MergeFn);
     Ok((
         sorter_into_reader(word_docids_sorter, indexer)?,
-        sorter_into_reader(empty_sorter, indexer)?,
+        sorter_into_reader(exact_word_docids_sorter, indexer)?,
     ))
 }

milli/src/update/index_documents/extract/mod.rs

@@ -43,6 +43,7 @@ pub(crate) fn data_from_obkv_documents(
     geo_field_id: Option<FieldId>,
     stop_words: Option<fst::Set<&[u8]>>,
     max_positions_per_attributes: Option<u32>,
+    exact_attributes: HashSet<FieldId>,
 ) -> Result<()> {
     let result: Result<(Vec<_>, (Vec<_>, Vec<_>))> = obkv_chunks
         .par_bridge()
@@ -90,7 +91,7 @@ pub(crate) fn data_from_obkv_documents(
         docid_word_positions_chunks.clone(),
         indexer.clone(),
         lmdb_writer_sx.clone(),
-        extract_word_docids,
+        move |doc_word_pos, indexer| extract_word_docids(doc_word_pos, indexer, &exact_attributes),
         merge_roaring_bitmaps,
         |(word_docids_reader, exact_word_docids_reader)| TypedChunk::WordDocids {
             word_docids_reader,

milli/src/update/index_documents/mod.rs

@@ -226,6 +226,7 @@ where
         };
 
         let stop_words = self.index.stop_words(self.wtxn)?;
+        let exact_attributes = self.index.exact_attributes_ids(self.wtxn)?;
 
         // Run extraction pipeline in parallel.
         pool.install(|| {
@@ -255,6 +256,7 @@ where
                     geo_field_id,
                     stop_words,
                     self.indexer_config.max_positions_per_attributes,
+                    exact_attributes,
                 )
             });