issue/43 Avoid keeping segments with 0 documents.

src/core/index.rs

@@ -243,7 +243,8 @@ impl Index {
         let mut searchers = Vec::new();
         for _ in 0..NUM_SEARCHERS {
             let searchable_segments_clone = searchable_segments.clone();
-            let segment_readers: Vec<SegmentReader> = try!(searchable_segments_clone.into_iter()
+            let segment_readers: Vec<SegmentReader> = try!(searchable_segments_clone
+                .into_iter()
                 .map(SegmentReader::open)
                 .collect());
             let searcher = Searcher::from(segment_readers);

src/indexer/index_writer.rs

@@ -155,16 +155,14 @@ fn index_documents(heap: &mut Heap,
     // this is ensured by the call to peek before starting
     // the worker thread.
     assert!(num_docs > 0);    
-    
-    segment
-        .meta_mut()
-        .set_num_docs(num_docs);
-    
+
     let doc_opstamps: Vec<u64> = segment_writer.finalize()?;
 
     // let segment_entry = advance_deletes(&mut segment, delete_queue, delete_position, )?;
+    let mut segment_meta = SegmentMeta::new(segment.id());
+    segment_meta.set_num_docs(num_docs);
 
-    let mut segment_entry = SegmentEntry::new(SegmentMeta::new(segment.id()));
+    let mut segment_entry = SegmentEntry::new(segment_meta);
     segment_entry.set_doc_to_opstamp(DocToOpstampMapping::from(doc_opstamps));
 
     segment_updater

src/indexer/merger.rs

@@ -83,9 +83,11 @@ impl IndexMerger {
         let mut readers = vec!();
         let mut max_doc = 0;
         for segment in segments {
-            let reader = SegmentReader::open(segment.clone())?;
-            max_doc += reader.num_docs();
-            readers.push(reader);
+            if segment.meta().num_docs() > 0 {
+                let reader = SegmentReader::open(segment.clone())?;
+                max_doc += reader.num_docs();
+                readers.push(reader);
+            }
         }
         Ok(IndexMerger {
             schema: schema,