After installing rpmdb-redhat, you need to do:
rpm --dbpath /usr/lib/rpmdb/i386-redhat-linux/redhat/ --rebuilddb
before it is useful for querying against.
Or, equivalently, query using
rpm --redhatprovides --dbapi 1
*** Bug 26015 has been marked as a duplicate of this bug. ***
fixed the script that builds rpmdb-redhat
*** Bug 28520 has been marked as a duplicate of this bug. ***