see code here https://github.com/teiid/teiid/blob/master/engine/src/main/resources/org/teiid/metadata/SYSADMIN.sql
Basically you can submit updateMatView with criteria, that gets mixed with materialization view transformation to do only updates
Regarding: SYSADMIN.updateMatView
what does this execute so to partially update the cache? If the same sql is run that was run when the load was done, the same result set will be processed, essentially all records. So is there an internal update process such that teiid will handle duplicates? Unless there's a way to set criteria to only pull new records, but I don't see an option like that.