data query - how can I create and modify its input method

[uopsdod]

I have a data query called 'CB'. I use it for QoS monitoring for interfaces on a host.
Recently, I want to know how Cacti collects those data by using this data query.
I found in the CB data query, it uses "Get Script Data (Indexed)" as its data input method. So, I start to look for data input method named "Get Script Data (Indexed)" but found nothing at all. Then, I go to one of the devices using this CB query, rolling down to the associated data query section, and click the "(Verbose Query) " for debugging in the CB query row. After that, I found sentences as following
''
+ Found data query XML file at '/usr/..../cacti/resource/script_queries/cb.xml'
+ XML file parsed ok.
+ Executing script for num of indexes 'perl /usr/..../cacti/scripts/cb.pl xxx.xxx.xxx.117 public_snmp num_indexes
''

Therefore, I know the CB data query is using /usr/..../cacti/scripts/cb.pl to collect data. It leads to my final questions:
1. If I want to use another script for this "Get Script Data (Indexed)" data input method, where can I modify the script path?
2. Why couldn't I find "Get Script Data (Indexed)" in data input methods?
3. What's "Get Script Data (Indexed)" about? is it different from normal data input method?

This gets me confused a lot.