if we need to copy all the functions of database to another database then how we can implement it other then copy paste and run it...Because there are total 153 functions in our database.
The tools provided to do what you want are pg_dump and pg_restore (specifically note the --list and --list-file options to pg_restore). You will need to manually edit the list file to include only the functions as there is no object type filter capability (well, I now see there is a --function argument to pg_restore but I'm unsure about whether it take wildcards. You will probably want to try it). You can restrict the dump to schema only if you indeed only care about functions.
