Your mySQL database sometimes has to create temporary tables and it usually does this in the system ‘/tmp’ folder. This is telling you, I believe, that it can not do that and the reason may be that the folder is full as it will have a limit imposed on it.

If you do not know how to empty it out I would ask your host support to do it ASAP. And perhaps ask them why they think it might be full if, indeed, that is the problem.

Thank you Andy.

I honestly don’t know what’s going on, but at the moment it’s working perfectly. No more errors.

So I will wait and see if it happens again, then I will contact the hosting.

I wouldn’t leave it. It may be that some space has been redeemed but there may still be garbage in the folder that could be removed.

I’ve been having this same issue, I get the “Invalid database query” message when trying to display the New/Recently updated topics combo, the logs show this:

file: sp-list-topic-class.php
line: 166
function: select
error: Can’t create/write to file ‘/tmp/#sql_5471_0.MYI’ (Errcode: 28)

I wrote to my hosting and asked them to free space on the tmp folder, but it’s been less than an hour and it seems to be full again

At the end of the day it really is something you need to discuss with your hosting support. Specifically why is the /tmp folder filling up so fast.

However – there is one thing you can look into. MySQL databases can get very fragmented and at some point this can be a real problem that can cause it to stop functioning altogether.  It becomes more likely that it will start to use space in the /tmp folder when it is in this state (as I understand it). The way to deal with this is to optimise your database and to keep it optimised.

You can do this in phpMyAdmin through your hosting control panel whenever you like but another good and useful way is to install something like the wp-dbmanager plugin which will allow you to optimise on demand but also set up a schedule so it gets done on a regular basis – like once weekly. Keeping it optimised will also boost its performance so it is a good thing to do whatever the problem.

But – it is still a question for your host if this doesn’t help.

Ok, I’ll try the plugin when I get home and I’ll let you know

let us know how it goes…  your host ought to be able to help with /tmp filling up too…

I installed the plugin and optimized the db but after a couple of days later I’m getting the same error from time to time, I’ve asked the hosting to empty the folder again and try to give the tmp folder more space, or maybe make the mysql use another folder with more space

Let’s see what they say

I’ve convinced them to increase the folder space, looks like it’s a shared folder not the tmp in my user…

I hope it works now

….

Well, they have now erased all the posts in my blog but that’s another fight… 

Joan Alamo Vallejo said
I’ve convinced them to increase the folder space, looks like it’s a shared folder not the tmp in my user…

I hope it works now

With shared hosting the chances are it is not even your site that is using up the space. You are basically at the mercy of all those other sites fighting for contention of resources.

Well, they have now erased all the posts in my blog but that’s another fight… 

How on earth can that happen? They should not really be in a position to effect data…