Contact search in Xperia Z doesn't show all contacts
I just got my Xperia Z and the contacts didn't seem to work properly in terms of filtering. The names were there when I scrolled through the list, but not all would show up if I filtered it with, say, the beginning letter. I enabled all ticks in the filter settings menu too.

Finally I figured that the ones not showing up were not assigned any group names like my contacts. They were showing as other contacts in Google contacts when I accessed the server through browser, but shown as undefined group inside android contacts, when I edited any of those contacts.

My solution was to log in to Google contacts server through browser, select other contacts group, click to select all, and add them to a group like say my contacts. Then log out from server. Go to Android Settings → Accounts, and force resync Google contacts by checking and checking the option. Wait for sync to finish. That's it. Now try Android contacts filter and it works properly!!!