Merge pull request #41 from meilisearch/sorter-into-reader-cursors

Introduce the `Sorter::into_reader_cursors` method

src/sorter.rs

@@ -19,7 +19,9 @@ const MIN_SORTER_MEMORY: usize = 10_485_760; // 10MB
 const DEFAULT_NB_CHUNKS: usize = 25;
 const MIN_NB_CHUNKS: usize = 1;
 
-use crate::{CompressionType, Error, Merger, MergerIter, Reader, Writer, WriterBuilder};
+use crate::{
+    CompressionType, Error, Merger, MergerIter, Reader, ReaderCursor, Writer, WriterBuilder,
+};
 
 /// The kind of sort algorithm used by the sorter to sort its internal vector.
 #[derive(Debug, Clone, Copy)]
@@ -596,23 +598,35 @@ where
     }
 
     /// Consumes this [`Sorter`] and outputs a stream of the merged entries in key-order.
-    pub fn into_stream_merger_iter(mut self) -> Result<MergerIter<CC::Chunk, MF>, Error<U>> {
+    pub fn into_stream_merger_iter(self) -> Result<MergerIter<CC::Chunk, MF>, Error<U>> {
+        let (sources, merge) = self.extract_reader_cursors_and_merger()?;
+        let mut builder = Merger::builder(merge);
+        builder.extend(sources);
+        builder.build().into_stream_merger_iter().map_err(Error::convert_merge_error)
+    }
+
+    /// Consumes this [`Sorter`] and outputs the list of reader cursors.
+    pub fn into_reader_cursors(self) -> Result<Vec<ReaderCursor<CC::Chunk>>, Error<U>> {
+        self.extract_reader_cursors_and_merger().map(|(readers, _)| readers)
+    }
+
+    /// A helper function to extract the readers and the merge function.
+    fn extract_reader_cursors_and_merger(
+        mut self,
+    ) -> Result<(Vec<ReaderCursor<CC::Chunk>>, MF), Error<U>> {
         // Flush the pending unordered entries.
         self.chunks_total_size = self.write_chunk()?;
 
-        let sources: Result<Vec<_>, Error<U>> = self
-            .chunks
+        let Sorter { chunks, merge, .. } = self;
+        let result: Result<Vec<_>, _> = chunks
             .into_iter()
             .map(|mut chunk| {
                 chunk.seek(SeekFrom::Start(0))?;
                 Reader::new(chunk).and_then(Reader::into_cursor).map_err(Error::convert_merge_error)
             })
             .collect();
 
-        let mut builder = Merger::builder(self.merge);
-        builder.extend(sources?);
-
-        builder.build().into_stream_merger_iter().map_err(Error::convert_merge_error)
+        result.map(|readers| (readers, merge))
     }
 }