private void addToCurrentFunctions(String functionName, FunctionInfo functionInfo) {
    if (SessionState.get() != null && functionInfo != null) {
      SessionState.get().getCurrentFunctionsInUse().put(functionName, functionInfo);
    }
  }
Looks up the function name in the registry. If enabled, will attempt to search the metastore
for the function.
@param functionName
@return
ql/src/java/org/apache/hadoop/hive/ql/exec/Registry.java