refactor spawn_extraction_task

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

@@ -26,7 +26,7 @@ use self::extract_word_pair_proximity_docids::extract_word_pair_proximity_docids
 use self::extract_word_position_docids::extract_word_position_docids;
 use super::helpers::{
     as_cloneable_grenad, keep_first_prefix_value_merge_roaring_bitmaps, merge_cbo_roaring_bitmaps,
-    merge_readers, merge_roaring_bitmaps, CursorClonableMmap, GrenadParameters, MergeFn,
+    merge_roaring_bitmaps, CursorClonableMmap, GrenadParameters, MergeFn, MergeableReader,
 };
 use super::{helpers, TypedChunk};
 use crate::{FieldId, Result};
@@ -66,7 +66,7 @@ pub(crate) fn data_from_obkv_documents(
         (docid_fid_facet_numbers_chunks, docid_fid_facet_strings_chunks),
     ) = result?;
 
-    spawn_extraction_task(
+    spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
         docid_word_positions_chunks.clone(),
         indexer.clone(),
         lmdb_writer_sx.clone(),
@@ -76,7 +76,7 @@ pub(crate) fn data_from_obkv_documents(
         "word-pair-proximity-docids",
     );
 
-    spawn_extraction_task(
+    spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
         docid_word_positions_chunks.clone(),
         indexer.clone(),
         lmdb_writer_sx.clone(),
@@ -86,7 +86,7 @@ pub(crate) fn data_from_obkv_documents(
         "field-id-wordcount-docids",
     );
 
-    spawn_extraction_task(
+    spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
         docid_word_positions_chunks.clone(),
         indexer.clone(),
         lmdb_writer_sx.clone(),
@@ -96,7 +96,7 @@ pub(crate) fn data_from_obkv_documents(
         "word-docids",
     );
 
-    spawn_extraction_task(
+    spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
         docid_word_positions_chunks.clone(),
         indexer.clone(),
         lmdb_writer_sx.clone(),
@@ -106,7 +106,7 @@ pub(crate) fn data_from_obkv_documents(
         "word-position-docids",
     );
 
-    spawn_extraction_task(
+    spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
         docid_fid_facet_strings_chunks.clone(),
         indexer.clone(),
         lmdb_writer_sx.clone(),
@@ -116,7 +116,7 @@ pub(crate) fn data_from_obkv_documents(
         "field-id-facet-string-docids",
     );
 
-    spawn_extraction_task(
+    spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
         docid_fid_facet_numbers_chunks.clone(),
         indexer.clone(),
         lmdb_writer_sx.clone(),
@@ -133,7 +133,7 @@ pub(crate) fn data_from_obkv_documents(
 /// Generated grenad chunks are merged using the merge_fn.
 /// The result of merged chunks is serialized as TypedChunk using the serialize_fn
 /// and sent into lmdb_writer_sx.
-fn spawn_extraction_task<FE, FS>(
+fn spawn_extraction_task<FE, FS, M>(
     chunks: Vec<grenad::Reader<CursorClonableMmap>>,
     indexer: GrenadParameters,
     lmdb_writer_sx: Sender<Result<TypedChunk>>,
@@ -142,19 +142,21 @@ fn spawn_extraction_task<FE, FS>(
     serialize_fn: FS,
     name: &'static str,
 ) where
-    FE: Fn(grenad::Reader<CursorClonableMmap>, GrenadParameters) -> Result<grenad::Reader<File>>
+    FE: Fn(grenad::Reader<CursorClonableMmap>, GrenadParameters) -> Result<M::Output>
         + Sync
         + Send
         + 'static,
-    FS: Fn(grenad::Reader<File>) -> TypedChunk + Sync + Send + 'static,
+    FS: Fn(M::Output) -> TypedChunk + Sync + Send + 'static,
+    M: MergeableReader + FromParallelIterator<M::Output> + Send + 'static,
+    M::Output: Send,
 {
     rayon::spawn(move || {
-        let chunks: Result<Vec<_>> =
+        let chunks: Result<M> =
             chunks.into_par_iter().map(|chunk| extract_fn(chunk, indexer.clone())).collect();
         rayon::spawn(move || match chunks {
             Ok(chunks) => {
                 debug!("merge {} database", name);
-                let reader = merge_readers(chunks, merge_fn, indexer);
+                let reader = chunks.merge(merge_fn, &indexer);
                 let _ = lmdb_writer_sx.send(reader.map(|r| serialize_fn(r)));
             }
             Err(e) => {

milli/src/update/index_documents/helpers/grenad_helpers.rs

@@ -78,25 +78,62 @@ pub unsafe fn as_cloneable_grenad(
     Ok(reader)
 }
 
-pub fn merge_readers<R: io::Read + io::Seek>(
+pub trait MergeableReader
-    readers: Vec<grenad::Reader<R>>,
+where
-    merge_fn: MergeFn,
+    Self: Sized,
-    indexer: GrenadParameters,
+{
-) -> Result<grenad::Reader<File>> {
+    type Output;
-    let mut merger_builder = grenad::MergerBuilder::new(merge_fn);
+
-    for reader in readers {
+    fn merge(self, merge_fn: MergeFn, indexer: &GrenadParameters) -> Result<Self::Output>;
-        merger_builder.push(reader.into_cursor()?);
+}
+
+impl MergeableReader for Vec<grenad::Reader<File>> {
+    type Output = grenad::Reader<File>;
+
+    fn merge(self, merge_fn: MergeFn, params: &GrenadParameters) -> Result<Self::Output> {
+        let mut merger = MergerBuilder::new(merge_fn);
+        self.into_iter().try_for_each(|r| merger.push(r))?;
+        merger.finish(params)
+    }
+}
+
+impl MergeableReader for Vec<(grenad::Reader<File>, grenad::Reader<File>)> {
+    type Output = (grenad::Reader<File>, grenad::Reader<File>);
+
+    fn merge(self, merge_fn: MergeFn, params: &GrenadParameters) -> Result<Self::Output> {
+        let mut m1 = MergerBuilder::new(merge_fn);
+        let mut m2 = MergerBuilder::new(merge_fn);
+        for (r1, r2) in self.into_iter() {
+            m1.push(r1)?;
+            m2.push(r2)?;
+        }
+        Ok((m1.finish(params)?, m2.finish(params)?))
+    }
+}
+
+struct MergerBuilder<R>(grenad::MergerBuilder<R, MergeFn>);
+
+impl<R: io::Read + io::Seek> MergerBuilder<R> {
+    fn new(merge_fn: MergeFn) -> Self {
+        Self(grenad::MergerBuilder::new(merge_fn))
     }
 
-    let merger = merger_builder.build();
+    fn push(&mut self, reader: grenad::Reader<R>) -> Result<()> {
-    let mut writer = create_writer(
+        self.0.push(reader.into_cursor()?);
-        indexer.chunk_compression_type,
+        Ok(())
-        indexer.chunk_compression_level,
+    }
-        tempfile::tempfile()?,
-    );
-    merger.write_into_stream_writer(&mut writer)?;
 
-    Ok(writer_into_reader(writer)?)
+    fn finish(self, params: &GrenadParameters) -> Result<grenad::Reader<File>> {
+        let merger = self.0.build();
+        let mut writer = create_writer(
+            params.chunk_compression_type,
+            params.chunk_compression_level,
+            tempfile::tempfile()?,
+        );
+        merger.write_into_stream_writer(&mut writer)?;
+
+        Ok(writer_into_reader(writer)?)
+    }
 }
 
 #[derive(Debug, Clone, Copy)]

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

@@ -8,9 +8,9 @@ use std::convert::{TryFrom, TryInto};
 pub use clonable_mmap::{ClonableMmap, CursorClonableMmap};
 use fst::{IntoStreamer, Streamer};
 pub use grenad_helpers::{
-    as_cloneable_grenad, create_sorter, create_writer, grenad_obkv_into_chunks, merge_readers,
+    as_cloneable_grenad, create_sorter, create_writer, grenad_obkv_into_chunks,
     sorter_into_lmdb_database, sorter_into_reader, write_into_lmdb_database, writer_into_reader,
-    GrenadParameters,
+    GrenadParameters, MergeableReader,
 };
 pub use merge_functions::{
     concat_u32s_array, keep_first, keep_first_prefix_value_merge_roaring_bitmaps, keep_latest_obkv,