Post images use wrong domain

Hi Folks,
I imported about 3 yrs worth of posts using the wordpress wxr file importer. It worked fine except for one small niggle – the post’s image urls still use the old domain. i.e they read:

https://www.oldsite.com/wp-content/uploads/2013/02/foo.jpg

instead of:

https://www.newsite.com/wp-content/uploads/2013/02/foo.jpg

Where is the domain set??

I cant see any settings in the SQL DB other than the ones I’ve already made sure are good in the options table. And it doesn’t appear to be contained in the posts table…

Thanks