Searching for pictures with only one character

Is there a way to do this using the tag system, like a search for pictures that only have one character tag?

If not, how hard would it be to add a tag ('1person' or something) to such pictures to make them easier to find?

solo

Considering the number of pictures this would effect, I doubt you'd ever get this to work well, both with new people tagging, and with the 340k previous posts that need to be looked at retrospectively.

I made a trac request for a metatag to do this, but it got a wontfix: http://trac.donmai.us/ticket/482

And it turns out that wasn't the first time something like that's been requested (and rejected): http://trac.donmai.us/ticket/199

Adding a "solo" tag just isn't a feasible solution.

No, the solo tag is not feasible. Having 1_character 2_character and upwards for just about every image is too much. It would need to be done using metatags if done at all. I've brought up a number of times my desire to get a way to search for images with 'x' occurances of 'y' metatag ("Give me all touhou images with two character tags assigned" for example) but I guess it's not feasible from a programming standpoint. =/ Even so, we don't want to start using things like solo.

So are you going to get rid of the existing 'solo' tag with ~1500 images?

We probably should. 1500 out of probably 150,000 eligible, at the very least, means it's not well known or used and isn't serving its purpose.