From 5e0c9b7c1ad44b92d5c634f5d4f4426f17864079 Mon Sep 17 00:00:00 2001
From: markwalkom <mark@walkom.id.au>
Date: Tue, 30 Oct 2018 20:22:42 +1100
Subject: [PATCH] Update reindex.asciidoc (#35062)

Highlighted that `_source` needs to exist in the source index.
---
 docs/reference/docs/reindex.asciidoc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/docs/reference/docs/reindex.asciidoc b/docs/reference/docs/reindex.asciidoc
index 314f63c7ada..bf8a2057b39 100644
--- a/docs/reference/docs/reindex.asciidoc
+++ b/docs/reference/docs/reindex.asciidoc
@@ -1,6 +1,9 @@
 [[docs-reindex]]
 == Reindex API
 
+IMPORTANT: Reindex requires <<mapping-source-field,`_source`>> to be enabled for
+all documents in the source index.
+
 IMPORTANT: Reindex does not attempt to set up the destination index.  It does
 not copy the settings of the source index.  You should set up the destination
 index prior to running a `_reindex` action, including setting up mappings, shard