Doc: enhance pgbench manual.

Clarify the difference between "prepared mode" and other query modes.

Discussion: https://postgr.es/m/20181030.103654.2249812451112831300[email protected]
Reviewed by: Fabien Coelh and Alvaro Herrera.

diff --git a/doc/src/sgml/ref/pgbench.sgml b/doc/src/sgml/ref/pgbench.sgml
index ca1608811881809227272eb176cb591023a90ee1..15ee7c0f2ba9e2fe46b850a33aeb646549001fd4 100644 (file)
--- a/doc/src/sgml/ref/pgbench.sgml
+++ b/doc/src/sgml/ref/pgbench.sgml
@@ -473,6 +473,13 @@ pgbench  options  d
             prepared: use extended query protocol with prepared statements.
            
           
+
+        Because in "prepared" mode pgbench reuses
+        the parse analysis result for the second and subsequent query
+        iteration, pgbench runs faster in the
+        prepared mode than in other modes.
+       
+       
         The default is simple query protocol.  (See 
         for more information.)