Predicates are a useful and powerful feature in dexter allowing users to filter the data passed to almost any function on arbitrarily complex combinations of the variables in the data base.
Depending on the package infrastructure, some users may have experienced problems with predicates recently. This is caused by changes in the most recent version of a dependency, dbplyr 1.4. We are talking to the developers of dbplyr. In the meanwhile, problems can be avoided by downgrading dbplyr to version 1.3.
Start a new R session and execute:
remove.packages(dbplyr) library(devtools) install_version("dbplyr", version="1.3.0")