Solr 4 Pro Tip
If you’ve upgraded to the alpha version of Solr 4 (as far as I can recall, this wasn’t a problem in the development trunk versions from a couple of months back), and you kept your schema.xml file, you may have noticed that deleteByQuery commands no longer work.
Here’s the simple fix (posted as an image because I can’t make damn Tumblr output code nicely).
Make sure that “version" statement is in your schema. I don’t know why it works, but it does.
Incidentally: if you’re using Solr through PHP, I recommend Solarium as an API. It seems to do just about everything, is well documented, and is updated with amazing frequency. It’s had support for Solr 4 features like join for some time now (although I believe I’m doing join manually).
I’ll detail how I’m using join in a later post.