I just got a new 2018 Macbook Pro, so I'm in the process of migrating from my 2013 MBP to the new one. I don't trust the Migration Assistant due to numerous bad past experiences, so I do this kind of thing manually.
To move my Messages content over, I copied the entire
~/Library/Messages/ directory over to the new machine, and Messages generally seems to work fine - all my messages are there, Text Forwarding from my phone works, etc. The one thing that doesn't work, is search. I can't search for anything at all, no matter what it is. 100% of attempted searches results in "No Results Found".
Is this a Spotlight issue? Is there some trick to make Messages' content searchable?