Make sure data always goes to new index

Fixes pypi#3746

Author: honzakral

warehouse/search/tasks.py

@@ -94,7 +94,10 @@ def _project_docs(db):
     for release in windowed_query(release_data, Release.name, 50000):
         p = ProjectDocType.from_db(release)
         p.full_clean()
-        yield p.to_dict(include_meta=True)
+        doc = p.to_dict(include_meta=True)
+        if '_index' in doc:
+            del doc['_index']
+        yield doc
 
 
 @tasks.task(ignore_result=True, acks_late=True)
@@ -143,7 +146,8 @@ def reindex(request):
     try:
         request.db.execute("SET statement_timeout = '600s'")
 
-        for _ in parallel_bulk(client, _project_docs(request.db)):
+        for _ in parallel_bulk(client, _project_docs(request.db),
+                               index=new_index_name):
             pass
     except:  # noqa
         new_index.delete()