Add some details to format_statement() help around the new statement_truncate_len variable within the new sys_config table

Author: MarkLeith

README.md

@@ -1379,7 +1379,9 @@ mysql> select format_path('/Users/mark/sandboxes/SmallTree/AMaster/data/mysql/pr
 
 ##### Description
 
-Formats a normalized statement, truncating it if it's > 64 characters long.
+Formats a normalized statement, truncating it if it's > 64 characters long by default.
+
+To configure the length to truncate the statement to by default, update the `statement_truncate_len` variable with `sys_config` table to a different value. Alternatively, to change it just for just your particular session, use `SET @statement_truncate_len := <some new value>`.
 
 Useful for printing statement related data from Performance Schema from the command line.
 

functions/format_statement.sql

@@ -25,7 +25,11 @@ CREATE DEFINER='root'@'localhost' FUNCTION format_statement (
              Description
              -----------
 
-             Formats a normalized statement, truncating it if it\'s > 64 characters long.
+             Formats a normalized statement, truncating it if it\'s > 64 characters long by default.
+
+             To configure the length to truncate the statement to by default, update the `statement_truncate_len`
+             variable with `sys_config` table to a different value. Alternatively, to change it just for just 
+             your particular session, use `SET @statement_truncate_len := <some new value>`.
 
              Useful for printing statement related data from Performance Schema from 
              the command line.