Sorry about not being able to provide the proper version. aptitude tells me I'm using:

kde-plasma-desktop at  5:90
plasma-desktop / plasma-workspace at 4:5.0.0
kde-base / kde-runtime at 4:4.11.3

If I go to the "About KDE" menu on KTorrent or Amarok it shows 4.14.21.

Anyway I'm using Debian testing with all packages up-to-date as of today.

Yesterday I updated my Debian packages normally and lost the functionality of the K menu (application launcher) where before the update it would give me results of applications or system setting modules. For example: if I wrote "ktor" it would show me ktorrent. If I wrote "composit" it would show me the Display And Monitor system configuration module (where you can configure compositing being enabled or not at startup).

If I go to Computer -> System Settings and type "composit" it works fine (showing me a few drop-down options and highlighting the relevant icon below).

Even if I write the full application name (konsole, for example) it won't produce results. Even with konsole written and pressing ENTER it also won't launch the command. KRunner is the same: I can press ALT+F2, write konsole and press ENTER repeatedly and nothing happens.

Maybe I'm missing a package on my installation? I don't install the full set of KDE packages from Debian so it could be that the new update is missing a dependency. If that is the case I'm asking for help identifying which one so I can open a follow-up bug on the Debian tracker. The application launcher search feature was working fine before the upgrade yesterday.

If I go to the Search system settings module it show all proper plugins activated (including Applications and System Settings among several others). File search is enabled too.

Reproducible: Always

Steps to Reproduce:
Case 1 (ktorrent)

1. Open Application Launcher
2. Where it says "Type to search..." type "ktor" or "ktorrent"

Case 2 (compositing)

1. Open Application Launcher
2. Where it says "Type to search..." type "compos" or "compositing"

Case 3 using KRunner (konsole)

1. Press ALT+F2
2. Where it says "search" type konsole (nothing is shown)
3. Press ENTER to run the command (nothing happens)

Actual Results:  
Case 1: Nothing is shown. Pressing ENTER doesn't launch the application if full name is specified.

Case 2: the command isn't launched, UI gives no feedback at all / is unchanged. Doing the same on the System Settings application internal search feature works as intended.

Case 3: the command isn't launched, UI gives no feedback at all / is unchanged

Expected Results:  
Case 1: show the KTorrent icon with partial or full name provided (case-insensitive).

Case 2: the respective system setting modules should be shown (depends on how much of "compositing" your write but the full word should show Desktop Effects and Display And Monitor).

Case 3: should run the specified command when the full name is given and ENTER is pressed (should probably show partial matches as a search feature too but I'm not sure since I never use KRunner / ALT+F2)

Repeating the steps above with the proper case also don't work (KTorrent, Konsole).

As mentioned above these functions stopped working (as far as I can tell) after upgrading all my installed packages yesterday via aptitude (apt/apt-get frontend on Debian). Today I've again upgraded some important KDE packages but the problem persists, even after a hard reboot to make sure everything is working as it should.