Performance tuning advice for SSI.

Kevin Grittner, with additional wordsmithing by me.

diff --git a/doc/src/sgml/mvcc.sgml b/doc/src/sgml/mvcc.sgml
index e688176acb4ce9e7fd2b3cd575edd84e25d9de58..1d337b80550d1b72b6b871017f393555b976a9a8 100644 (file)
--- a/doc/src/sgml/mvcc.sgml
+++ b/doc/src/sgml/mvcc.sgml
@@ -658,6 +658,26 @@ ERROR:  could not serialize access due to read/write dependencies among transact
        protections automatically provided by Serializable transactions.
       
      
+     
+      
+       When the system is forced to combine multiple page-level predicate
+       locks into a single relation-level predicate lock because the predicate
+       lock table is short of memory, an increase in the rate of serialization
+       failures may occur.  You can avoid this by increasing
+       .
+      
+     
+     
+      
+       A sequential scan will always necessitate a relation-level predicate
+       lock.  This can result in an increased rate of serialization failures.
+       It may be helpful to encourage the use of index scans by reducing
+        and/or increasing
+       .  Be sure to weigh any decrease
+       in transaction rollbacks and restarts against any overall change in
+       query execution time.
+      
+