Re: Suppressing src block evaluationon publish?

From: Dan Davison <dandavison7@gmail.com>
To: Loris Bennett <loris.bennett@fu-berlin.de>
Cc: emacs-orgmode@gnu.org
Subject: Re: Suppressing src block evaluationon publish?
Date: Thu, 03 Feb 2011 10:38:08 +0000	[thread overview]
Message-ID: <m17hdhwghb.fsf@94.197.213.136.threembb.co.uk> (raw)
In-Reply-To: <87bp2t34z3.fsf@slate.zedat.fu-berlin.de> (Loris Bennett's message of "Thu, 03 Feb 2011 09:19:28 +0100")

Loris Bennett <loris.bennett@fu-berlin.de> writes:

> Erik Iverson <eriki@ccbr.umn.edu> writes:
>
>> Loris Bennett wrote:
>>> Hi,
>>>
>>> I have an org file containing several src blocks which generate images
>>> using ditaa. When I publish to PDF via LaTeX, the images are all
>>> generated every time, which makes publishing rather slow.
>>>
>>> Is there some way to toggle the evaluation of the src blocks on and off
>>> when the file is published?
>>>
>>
>> You could try the :cache header argument, http://orgmode.org/org.html#cache
>>
>
> Ah, thanks. There is a slight gotcha here, though.
>
> I added :cache yes to the source headers and exported again, but nothing
> changed; all the images were generated again. Also, no SHA1 hash was
> added to the +results header.
>
> After some fruitless fiddling I was about to write to the list again and
> moan, when I did a slightly random C-c C-c in the begin_src line and,
> hey presto, the hash was added to the results header. I then did this
> for all the images and found that the image were no longer regenerated
> on export, as advertised.

Hi Loris,

Yes. It does seem that it would be nice if in this situation, the first
export added the SHA1s, and subsequent exports recognized that
evaluation wasn't required. I think the reason this does not happen is
that behind-the-scenes Org makes a copy of the buffer for export
preprocessing (including src block evaluation). But Eric S is the expert
-- he may have more to say here.

A couple of things that might be relevant here: the variable
`org-export-babel-evaluate' can also be used to prevent evaluation on
export (but the :cache approach has advantages). And C-c C-v C-b / C-c
C-v C-s (`org-babel-evaluate-buffer' / `org-babel-execute-subtree')
could be used to update the SHA1s.

> Perhaps the documentation of :cache could be extended to mention the
> necessity of evaluating the source block before exporting.

I've added that to the TODO list.

Dan

>

>
> Loris
>>
>>
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