How to clear iMessage history
When I use the search function n my iPad it shows all of my previous iMessages even though I have deleted all the messages from iMessages.
iPad 2
You cannot remove those from the Spotlight Seach cache. The only way to completely remove them would be to reset to factory settings and start all over again.
Besides, if you tap on that message in the search and open the messages app, it will no longer show the message itself.