Hello Statalisters

I am using the command -join- from the package -ftools-, from SSC, in Stata 14.0 to speed up some code on a dataset of ~4 million observations. The following pseudocode is causing a problem:

Code:
save "`full_ds'"

(transform and collapse the data)

join, into("`full_ds'") by(year)
Stata returns the following error message:

Code:
(obs: 16; levels: 16; method: hash0; dict size: 16)
invalid file specification
stata(): 3598 Stata returned error
join(): - function returned error
<istmt>: - function returned error
I have tried saving the file to disk, instead of creating a temprorary file, this hasn't helped. I have tried using a traditional -merge 1:m-, this works just fine, but will be much too slow on my full dataset. I have also tried uninstalling and re-installing -ftools-, to no avail.

Googling tells me that "3598" is a mata error, however I have decided to post my question here as I presume the error is in my use of stata, not the underlying mata code. Any suggestions to help me find the source of this problem are much appreciated.