Update v2.16.4 release notes with the reindex note
The fix Ic59e4d330f introduces a Lucene schema upgrade that needs
to be mentioned in the release notes.
Change-Id: I3def05355e7283be8915a658ae6e68cff454f475
diff --git a/pages/site/releases/2.16.md b/pages/site/releases/2.16.md
index 4e491bd..35a5058 100644
--- a/pages/site/releases/2.16.md
+++ b/pages/site/releases/2.16.md
@@ -490,6 +490,34 @@
### 2.16.4
+### Reindex for projects, accounts and groups indexes.
+
+Gerrit 2.16.4 includes a fix to the projects, accounts, and groups secondary indexes.
+It is very unusual for Gerrit to require a reindex inside a point release.
+However, this is an exception because it is the only solution to fix the list sorting
+[Issue 10210](https://bugs.chromium.org/p/gerrit/issues/detail?id=10210) reported on PolyGerrit.
+
+The reindex of projects, accounts and groups can be performed either offline or online.
+For the offline reindex, make sure that Gerrit is not active and run the followign commands:
+
+``` sh
+ java -jar gerrit.war reindex --index projects -d ${site_path}
+ java -jar gerrit.war reindex --index groups -d ${site_path}
+ java -jar gerrit.war reindex --index accounts -d ${site_path}
+```
+
+The online reindex does not require any commands: upgrade the gerrit.war
+and restart Gerrit.
+
+**NOTE**: The online reindex for projects may take quite a long time and
+require a substantial amount of heap memory to run. During the reindex operation,
+Gerrit performance may be sluggish and, even after the reindex is complete,
+it would take quite some time for the memory to be released.
+It is thus recommended to perform the offline reindex, to avoid impacting the
+server performance at startup and after the reindex is complete.
+
+### Fixes
+
#### PolyGerrit
* [Issue 9909](https://bugs.chromium.org/p/gerrit/issues/detail?id=9909):
