MDL-60174 Document new dboption in config-dist.php

config-dist.php

@@ -70,6 +70,15 @@ $CFG->dboptions = array(
                                 // can be removed for MySQL (by default it will
                                 // use 'utf8mb4_unicode_ci'. This option should
                                 // be removed for all other databases.
+    // 'fetchbuffersize' => 100000, // On PostgreSQL, this option sets a limit
+                                // on the number of rows that are fetched into
+                                // memory when doing a large recordset query
+                                // (e.g. search indexing). Default is 100000.
+                                // Uncomment and set to a value to change it,
+                                // or zero to turn off the limit. You need to
+                                // set to zero if you are using pg_bouncer in
+                                // 'transaction' mode (it is fine in 'session'
+                                // mode).
 );