On large Cacti installs, editing Data Templates is slow #4135
Description
Describe the bug
On large systems, the Cacti GUI appears real slow when editing Data Templates.
Expected behavior
Cacti should remain as performant on large systems as small systems.
Additional context
There is a query that is requesting a list of all Data Sources that match the Data Template rather than seeing simply if there is one. This results in high memory usage, and a very slow GUI.