All category functionality lost after upgrade to 2.6.2

Oh, and all the links disappeared as well.

They’re still in the database – they just don’t show up on the site.

Unfortunately this was a terrible problem a lot of people had when upgrading to WP 2.6+ when you went from certain older versions of WP.

I think it worked right for those who upgraded every step of the way (WP 2.5.1 etc)

There are numerous threads & blog posts on other websites explaining ways of fixing it. Far as I know you have to go into your SQL database using phpMyAdmin.

It has to do with the categories, taxonomy tables in the database.

I do not know if this blog has the best answer, but this is one blog that tries to explain how to fix it:

https://blog.cumps.be/wordpress-26-upgrade-fix-missing-categories/

Hope this helps! If anyone knows an easier way, please post it!

Well… no. David Cump’s solution doesn’t work for me.

Weirdly, the links are all still there, and browse-able in wp_links. They have the category id field populated, and the link categories still seem to be there in wp_terms. However, the category # in wp_links doesn’t seem to match the category # in wp_terms.

What strikes me as bizarre is that I can add categories in wp-admin, but they just don’t seem to “stick” to the posts.

Another oddity – whenever I edit a post, it seems to create a new copy of the post in the database. If I carry out 7 edits, 7 copies of the post are created. Only the first (unaltered) copy is shown on the website, however.

the extra copies in the database has to do with the new (WP 2.6+) feature called “Post Revisions”

If you don’t want that action, there are 2 plugins that can disable it, or a manual code method described here,
https://lesterchan.net/wordpress/2008/07/17/how-to-turn-off-post-revision-in-wordpress-26/

I don’t know whether this would solve your other issues, or if this will even help. You might like that feature.

gpvillamil, did you ever figure out why your categories didn’t “stick” when you selected them for a post? If so, how did you fix it? I am having the same problem and I am at a dead-end and could really use some help!
Thanks! ??

I was able to fix everything after all.

My website had actually been hacked – there was a bunch of hidden metadata in the index page, pointing to a variety of dodgy pharmaceuticals and Viagra sites.

Clearly, whoever hacked the site also tampered with the database structure, and this was probably the cause of the problem.

So I backed up my SQL database, deleted it from the server, and installed WordPress from scratch. I then restored each individual table from the backup – data only, no preferences or anything like that. I used a text editor to go through the database and identify each individual table, splitting them out into separate files.

Once done, everything worked again, even post numbers and permalinks.

It was a while ago, and I didn’t keep track of what I did in too much detail, otherwise I’d post step-by-step instructions.