I thought I have already explained it. Here it goes again. Demo page is: http://dbfiddle.uk/?rdbms=postgres_9.6&fiddle=ea61e7e1859bdb 7f297f853a9dc0e3d0
Now that you've posted the right link it becomes a bit easier to follow...
To summarize: I wanna use a pattern matching the only returns these rows:/testfile/client/10/attachment/1000/master/
/testfile/client/10/attachment/unassigned/file/ 1001/master
/testfile/client/10/attachment/unassigned/file/ 1002/master
Why isn't 7 valid?
Requiring that the last directory be the word master, with or without a forward slash, is simple enough but 7 matches that. Just tack the following onto the end of your existing pattern.
.+master/?$
I'd be more helpful but my iPad and the fiddle don't seem to play nicely together...
David J.