quoted

Actually it is possible. Check out David's response to my question from
some time ago:
http://permalink.gmane.org/gmane.comp.file-systems.btrfs/14227

this was a quick aid, please see attached file for an updated tool to set
the file flags, now added 'z' for NOCOMPRESS flag, and supports chattr
syntax plus all of the standard file flags.

Setting and unsetting nocow is done like 'fileflags +C file' or -C for
unseting. Without any + or - options it prints current state.

I get the following errors when running fileflags on large (>2GB) database files:

open(): No such file or directory

open(): Value too large for defined data type