Problem

-- padding characters missing in map expression
-- e.g: if X is "     " fixed field with space as padding char, "A" & X & "B" will result in "AB" instead of "A     B"

Resolution

* padding characters are removed by the parser and added by the builder(parser in output).

* X's value is NULL. "A" & NULL & "B" = "AB"

* cleverly use DML String functions(padString, replaceIfNull, ..., to resolve