Last tested: Dec 3, 2017
Fortunately, when migrating to SAML there is an option to merge from LDAP. So this should be quite simple.
There was once an unfortunate case where some users had different emails in the LDAP system and the SAML system. The best way to fix this kind of thing is to create a new credentials_email for the user via the api and set that to have the email address that you want for that user in SAML. Then, in the SAML setup, add ‘email’ to the ‘merge by’ list. (If you already had that user try to log in with SAML and it created a new user object that you didn’t want, then you have to delete that new un-needed user object.) Then, when the person logs in Looker should find that credentials_email with the matching email address for the user and merge the new SAML login info to that existing user account.