DRILL-5330: NPE in FunctionImplementationRegistry
Fixes:
* DRILL-5330: NPE in
FunctionImplementationRegistry.functionReplacement()
* DRILL-5331:
NPE in FunctionImplementationRegistry.findDrillFunction() if dynamic
UDFs disabled
When running in a unit test, the dynamic UDF (DUDF) mechanism is not
available. When running in production, the DUDF mechanism is available,
but may be disabled.
One confusing aspect of this code is that the function registry
is given the option manager, but the option manager is not yet valid
(not yet initialized) in the function registry constructor. So, we
cannot access the option manager in the function registry constructor.
In any event, the existing system options cannot be used to disable DUDF
support. For obscure reasons, DUDF support is always enabled, even when
disabled by the user.
Instead, for DRILL-5331, we added a config option to "really" disable DUDFS.
The property is set only for tests, disables DUDF support.
Note that, in the future, this option could be generalized to
"off, read-only, on" to capture the full set of DUDF modes.
But, for now, just turning this off is sufficient.
For DRILL-5330, we use an existing option validator rather than
accessing the raw option directly.
Also includes a bit of code cleanup in the class in question.
The result is that the code now works when used in a sub-operator unit
test.
close apache/drill#777
