Re: PSPP-BUG: 'Undo" function in PSPP?

From: John Darrington <john@darrington.wattle.id.au>
Sent: Wednesday, October 6, 2021 12:13 AM
To: Lane, Jonathan D. <jonathan.lane@vanderbilt.edu>
Cc: bug-gnu-pspp@gnu.org <bug-gnu-pspp@gnu.org>
Subject: Re: PSPP-BUG: 'Undo" function in PSPP?

On Tue, Oct 05, 2021 at 09:40:10PM +0000, Lane, Jonathan D. wrote:

     Thank you for maintaining and updating PSPP. There doesn't appear to be
     an "undo" function in the 9-5-2020 version of PSPP for Windows. "Undo"
     and "Redo" buttons/functions are common features of most programs. Is
     there indeed an "undo" function in the program?

Short answer: Not in the place that you're probably wanting it.

There is an Undo/Redo feature in the syntax editor, so that you can Undo/Redo
edits you have made there.

There is no such feature for the data editor, for a simple reason: Since
transformations in the data editor are in general non-reversable, the only
way to implement such a feature would be to keep a copy of the entire dataset,
so that it can be restored on Undo.   Datasets in PSPP can be enormous - larger
than the available memory of the machine, and in the case of datasets which
come from external sources such as a database connection, large that the local
machine's disk. A copy would need to be kept before every transformation, which
for a large dataset would rapidly exhaughst the space needed to keep it.

J'

From:	Lane, Jonathan D.
Subject:	Re: PSPP-BUG: 'Undo" function in PSPP?
Date:	Wed, 6 Oct 2021 05:46:22 +0000