According to RFC 6241, NETCONF should support reading of multiple subtrees using single get/get-config RPC request. See following examples:

• Reading just specific elements under all list items:
  https://tools.ietf.org/html/rfc6241#section-6.4.6
• Selection of multiple composite subtrees:
  https://tools.ietf.org/html/rfc6241#section-6.4.7

Current implementation of NETCONF in ODL supports only construction of simple subtree filter based on one YangInstanceIdentifier path.

On RESTCONF side, there is 'fields' query parameter that can be used for testing of this feature - most, if not all patterns that can be built using fields query parameter can be emulated using subtree filtering; see details:

• https://tools.ietf.org/html/rfc8040#section-4.8.3

What should be done:

• construction of more complex NETCONF subtree filters based on one parent path and list of subpaths that select specific fields that must be read
• exposing a new read method to NETCONF DOM API (DOMDataBroker extension and raw NETCONF service); for example: read(datastore, yiid, list<yiid>)
• creation of 'fields' query parameter parser that would return List<YangInstanceIdentifier> collection
• connection of RESTCONF and NETCONF sides

Use case:

• we need to read just selected leaves under all list items
• in NETCONF device, there are nearly 5000 list items an each of this list item has next containers; however we don't need all data
• because of the efficiency we would like to use just single RPC and minimize the network traffic

Note: similar ticket on ONAP JIRA:

• https://jira.onap.org/browse/SDNC-1367