refactor spawn_extraction_task

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>(
-    readers: Vec<grenad::Reader<R>>,
-    merge_fn: MergeFn,
-    indexer: GrenadParameters,
-) -> Result<grenad::Reader<File>> {
-    let mut merger_builder = grenad::MergerBuilder::new(merge_fn);
-    for reader in readers {
-        merger_builder.push(reader.into_cursor()?);
+pub trait MergeableReader
+where
+    Self: Sized,
+{
+    type Output;
+
+    fn merge(self, merge_fn: MergeFn, indexer: &GrenadParameters) -> Result<Self::Output>;
+}
+
+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();
-    let mut writer = create_writer(
-        indexer.chunk_compression_type,
-        indexer.chunk_compression_level,
-        tempfile::tempfile()?,
-    );
-    merger.write_into_stream_writer(&mut writer)?;
+    fn push(&mut self, reader: grenad::Reader<R>) -> Result<()> {
+        self.0.push(reader.into_cursor()?);
+        Ok(())
+    }
 
-    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)]