Expose new segment meta from Index (#637)

src/core/index.rs

@@ -216,8 +216,22 @@ impl Index {
         Index::open(mmap_directory)
     }
 
-    pub(crate) fn inventory(&self) -> &SegmentMetaInventory {
-        &self.inventory
+    /// Returns the list of the segment metas tracked by the index.
+    ///
+    /// Such segments can of course be part of the index,
+    /// but also they could be segments being currently built or in the middle of a merge
+    /// operation.
+    pub fn list_all_segment_metas(&self) -> Vec<SegmentMeta> {
+        self.inventory.all()
+    }
+
+    /// Creates a new segment_meta (Advanced user only).
+    ///
+    /// As long as the `SegmentMeta` lives, the files associated with the
+    /// `SegmentMeta` are guaranteed to not be garbage collected, regardless of
+    /// whether the segment is recorded as part of the index or not.
+    pub fn new_segment_meta(&self, segment_id: SegmentId, max_doc: u32) -> SegmentMeta {
+        self.inventory.new_segment_meta(segment_id, max_doc)
     }
 
     /// Open the index using the provided directory

src/core/index_meta.rs

@@ -30,7 +30,6 @@ impl SegmentMetaInventory {
             .collect::<Vec<_>>()
     }
 
-    #[doc(hidden)]
     pub fn new_segment_meta(&self, segment_id: SegmentId, max_doc: u32) -> SegmentMeta {
         let inner = InnerSegmentMeta {
             segment_id,

src/indexer/index_writer.rs

@@ -209,10 +209,7 @@ fn index_documents(
     assert!(num_docs > 0);
 
     let doc_opstamps: Vec<Opstamp> = segment_writer.finalize()?;
-    let segment_meta = segment
-        .index()
-        .inventory()
-        .new_segment_meta(segment_id, num_docs);
+    let segment_meta = segment.index().new_segment_meta(segment_id, num_docs);
 
     let last_docstamp: Opstamp = *(doc_opstamps.last().unwrap());
 

src/indexer/segment_updater.rs

@@ -126,9 +126,7 @@ fn perform_merge(
 
     let num_docs = merger.write(segment_serializer)?;
 
-    let segment_meta = index
-        .inventory()
-        .new_segment_meta(merged_segment.id(), num_docs);
+    let segment_meta = index.new_segment_meta(merged_segment.id(), num_docs);
 
     let after_merge_segment_entry = SegmentEntry::new(segment_meta.clone(), delete_cursor, None);
     Ok(after_merge_segment_entry)
@@ -282,7 +280,7 @@ impl SegmentUpdater {
     fn list_files(&self) -> HashSet<PathBuf> {
         let mut files = HashSet::new();
         files.insert(META_FILEPATH.to_path_buf());
-        for segment_meta in self.0.index.inventory().all() {
+        for segment_meta in self.0.index.list_all_segment_metas() {
             files.extend(segment_meta.list_files());
         }
         files