<optional> cannot be used here, because psql doesn't handle it.

diff --git a/doc/src/sgml/ref/cluster.sgml b/doc/src/sgml/ref/cluster.sgml
index 5c6581166995c67c3ff65a599c5e724dce118267..6e9e5bf502f56aecdc1b43e3457f110469158726 100644 (file)
--- a/doc/src/sgml/ref/cluster.sgml
+++ b/doc/src/sgml/ref/cluster.sgml
@@ -20,7 +20,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-CLUSTER <replaceable class="PARAMETER">tablename</replaceable> <optional> USING <replaceable class="PARAMETER">indexname</replaceable> </optional>
+CLUSTER <replaceable class="PARAMETER">tablename</replaceable> [ USING <replaceable class="PARAMETER">indexname</replaceable> ]
 CLUSTER
 </synopsis>
  </refsynopsisdiv>