Alfred takes longer to show results, database disk image is malformed I don't know why, but about a week ago I started seeing a lot of errors like this in system.log:

9/15/12 5:55:21.769 AM Alfred[263]: DB Query: select item, count(item) as used from knowledge where ts &gt; ? and item in (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?) group by item
9/15/12 5:55:21.769 AM Alfred[263]: DB Error: 11 "database disk image is malformed"


It would occasionally take about a second for files to show up in the result list.

Deleting the Spotlight index didn't help, but then I noticed that the usage tab didn't display any statistics either:



I think I solved it by just pressing the reset knowledge button. But I didn't find search results for this issue, so I'm answering this question myself.
So, pressing the reset knowledge button in the preferences seems to have fixed it.

If you get similar errors, you could also try removing ~/Library/Application Support/Alfred/knowledge.alfdb or other database files. If you're using a sandboxed version bought from the App Store, they are in ~/Library/Containers/com.alfredapp.Alfred/Data/.