Accidentally Deleting Forums Vocabulary in Categories Breaks Forums?

Good catch vincent, this is a bug. Here's what happens:

1) Forum vocabulary is created in forum.module, function _forum_get_vid(). This adds 3 pieces of data to the database, adding entries to the tables variable, vocabulary, and vocabulary_node_types.
2) The user visits the categories admin screen (or just clicks around the site for a while); another piece of data is added to the database in the form of cached variables from the variable table (forum_nav_vocabulary).
3) The user deletes the forum vocabulary via the admin/categories interface and 2 pieces of data are removed; the entries in vocabulary and vocabulary_node_types. Remaining are the entries in variable and cache.

The bug is that the variable forum_nav_vocabulary is outdated, a remnant from earlier times.

Code like this gets called 5 times in the forum.module:

$vid = variable_get('forum_nav_vocabulary', '');

Every instance should be replaced with a call to _forum_get_vid(). The function _forum_get_vid() needs to be rewritten so that it uses the following query to get the vid instead of variable_get. Since variables are cached statically to improve performance, these changes alone would result in degraded performance as we'd be querying the db every time we needed the forum vid. To fix this you can cache the vid statically in _forum_get_vid().

db_query("SELECT vid FROM {vocabulary_node_types} WHERE type = '%s'", 'forum');

Vincent, do you want to "roll a patch" for this?

PS - you can see the cached variables in the cache table. Feel free to empty your cache table outright (truncate) as these values will be rebuilt as needed.

Live database: clear cache table, erase the forum vocabulary variable entry from variable table. Then it should work (after the patch).

Bumping to CVS since it affects 4.6.* and CVS

I still had this problem in 4.6.3. after delving into the variables table I have found this workaround:

-Create a new forum vocablulary, called forums, type:forum topic, Hierarchy: Disabled
-In the vocabulary table find the vid of the forum vocabulary
-In the variables table edit forum_nav_vocabulary to s:1:"x"; where x is the vid of the forum vocab.
-You may need to empty the cache table

This may make existing forum posts unreachble, but atleast the forum will be functional again.

changing status to cvs.

I'm thinking the best thing to do is exclude this vocabulary from taxonomy.module's interface, so have created a new issue, "Remove vocabulary and term handling from taxonomy module for vocabularies assigned to other modules", http://drupal.org/node/38221.

This is still happening in 4.6.4 - is this correct?

Please use this thread to sort this issue out. This is an issue with the taxonomy module and the pros and cons seem to be more generically discussed in the other issue.

Marking this as a dupe, even though it isn't :P

Thanks for reporting this in basicmagic :)

Cheers
-K

Dave's suggestion in #6, above, does not work in my case. I cannot create containers now that actually show up.

-rich

I was able to get my forums back, I think. I ended up deleting all of the forums and containers from the admin interface because they didn't have any posts in them yet.

The procedure I followed, using phpmyadmin:

1) Create a vocabulary type called "forums" that has a single node type...
2) Reset the VID (vocabulary ID) for the forums entry in the vocabulary table to 1. Other boolean fields should all be zero for the row.
3) Edit the vocabulary_node_types table and change the entry that associated forum with the ID number you changed in step 2. In my case I had to change the number "17" back to 1; the correct value is probably 1
4) Go to admin/forum and Create a container and note the id number of the container you created
5) Fix the containers by resetting the value in the table "variables" and
name: forum_containers
value: a:1:{i:0;i:"insert-numeric-value-in-quotes";}

The stuff within the brackets includes weighting info for the containers. The 0 is thus a weight of zero.

After I did this my containers showed up again at www.site.org/forum

-rich

changing status to cvs.

Ooo.. a 4.6.1 issue survives to 7.x. Can someone verify if this bug still exists in either 6.x or 7.x?

As the one who brought this up again in #206820: Relocate or delete topics on forum deletion to avoid leaving stale data in database. because I had some kind of similar problem (solved http://drupal.org/node/509604) I tried to recreate this on my local instal. I failed...which is a good news.

I think this problem was solved by makeing the forums vocabulary indelible as long as the forum module is enabled. Disabling the module allows you to delete the vocab but reenabling recreates it automatically.

In my case above the problem was that for some reason the forum_nav_vocab entry in the variables table was not created on the first try. I had to try again and this created everything correctly. Any other hassles were due to i18n misconfigurations on my side.