Looks like I solved the problem on my machine thanks to a recent post in Ubuntu subreddit.
The post was titled: How I sped up my Ubuntu Dash. The user had problems with Dash being very slow to show him search results and he found out that the culprit was Zeitgeist. This thing tracks the files, applications you used and your other activities. It turned out that his Zeitgeist history was over two years long! When I checked on my system I had it dating back to February 2012 so it was even longer than his. I deleted the folder /home/your_user_name/.local/share/zeitgeist (almost 700 MB of data) containing the Zeitgeist history just like he did and I confirm that it sped up Dash. But it also resolved the problem described in this bug report. http://www.reddit.com/r/Ubuntu/comments/2ysuqu/how_i_sped_up_my_ubuntu_dash/ -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to unity in Ubuntu. https://bugs.launchpad.net/bugs/1308037 Title: No results from application scope Status in LibUnity: Confirmed Status in Unity: Confirmed Status in Unity Applications Lens: Confirmed Status in unity package in Ubuntu: Confirmed Bug description: Unity is in a state where I don't get any results from the applications lens. This sometimes happens for one search but either re-entering the search or toggling the lens has always fixed it in the past for me. This time neither of these steps work. I'm attaching a bustle log of the problem in case that's helpful. I searched for "spotify", which I've got installed, and got 0 results. The only way to fix the issue is to log out and back in. ProblemType: Bug DistroRelease: Ubuntu 14.04 Package: unity 7.2.0+14.04.20140411-0ubuntu1 ProcVersionSignature: Ubuntu 3.13.0-23.45-generic 3.13.8 Uname: Linux 3.13.0-23-generic x86_64 ApportVersion: 2.14.1-0ubuntu2 Architecture: amd64 CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins' CurrentDesktop: Unity Date: Tue Apr 15 13:29:40 2014 InstallationDate: Installed on 2012-10-07 (554 days ago) InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Beta amd64 (20121007) SourcePackage: unity UpgradeStatus: Upgraded to trusty on 2013-05-07 (343 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/libunity/+bug/1308037/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp