I understand your use case, but a leaf of type leafref does not in general identify a single node in the data tree - the leafref path could be for a non-key leaf, and/or the path could traverse list nodes, and/or the "target" list could have multiple keys and thus multiple leafref-leafs be required to identify a specific list entry.
Thus it seems to me that your use case is not a reasonable basis for a new protocol operation. My XPath foo isn't very good either, but I do believe Robert's suggestion of using an XPath filter could be a way forward. I *think* the filter expression would be something along the lines of /te/tunnels/tunnel[name='foo'] | /te/explicit-paths/explicit-path[name=/te/tunnels/tunnel[name='foo']/paths/path/explicit-path] --Per On 2017-10-09 15:42, Xufeng Liu wrote: > Hi Per, > > > > *From:* Igor Bryskin [mailto:[email protected]] > *Sent:* Sunday, October 8, 2017 7:04 PM > *To:* Igor Bryskin <[email protected]>; [email protected]; > [email protected] > *Cc:* [email protected]; [email protected] > *Subject:* Re: [Netconf] [netmod] Retrieving Information Pointed by leafref > > > > > Hi Joel, > > Thanks, I think I didnt explain our problem correctly. > > In our case we have a leafref pointing to a te tunnel name, which happens to > be a key to lookup the (axilary) tunnel. We need a way to include the > entire tunnel body (not just a name) into the get > response. This is to optimize the number of iterations between the client and > the server. As Xufeng put it something similar to SQL join, > > Igor > > *From:*Igor Bryskin > > *To:*[email protected],[email protected], > > *Cc:*[email protected],[email protected], > > *Date:*2017-10-08 17:36:47 > > *Subject:*Re: [Netconf] [netmod] Retrieving Information Pointed by leafref > > > > Hi Per, > > In a nutshell we would lika for a netconf client to have a way to instruct > the server on whether in response to the get request the server needs to > provide the entire body of a datastore node pointed > to by a leafref or just a pointer to said node, so that the node's body could > be retrieved by a subsequent separate request. This is requested by > implementors who want to optimise rhe number of > interactions between a client and its server. > > Cheers, > Igor > > *From:*Per Hedeland > > *To:*Xufeng Liu, > > *Cc:*[email protected],'NetMod WG', > > *Date:*2017-10-08 14:01:27 > > *Subject:*Re: [Netconf] [netmod] Retrieving Information Pointed by leafref > > > > On 2017-10-06 23:11, Xufeng Liu wrote: >> During the design team discussion for TE and MPLS YANG modeling, we have >> received a request from implementers: How to minimize the number of >> NETCONF/RESTCONF RPCs to improve operation efficiency? >> Especially for the case when the operator or client software needs to >> retrieve the object contents pointed by a leafref. >> >> For example, given the following simplified TE tunnel model, >> >> +--rw te >> >> +--rw explicit-paths >> >> | +--rw explicit-path* [name] >> >> | +--rw name string >> >> | +--rw explicit-route-object* [index] >> >> | +--rw index uint32 >> >> | +--rw explicit-route-usage? identityref >> >> +--rw tunnels >> >> | +--rw tunnel* [name] >> >> | | +--rw name string >> >> | | +--rw paths >> >> | | | +--rw path* [name] >> >> | | | +--rw explicit-path? -> >> ../../../../../explicit-paths/explicit-path/name >> >> when the client tries to retrieve a tunnels information based on the tunnel >> name, the get operation returns a list of leafrefs pointing to the paths of >> the tunnel. > > Sorry, I'm afraid I don't follow. Can you explain exactly what your > "get" request is (protocol and payload), and where the "list of > leafref's" (whatever that may be) occurs in the reply? > > */[Xufeng] The get operation is the NETCONF/RESTCON <get> protocol > operation, or the <get-data> operation described in > https://tools.ietf.org/html/draft-dsdt-nmda-netconf-01 and the GET operations > on {+restconf}/ds/<datastore> described in > https://tools.ietf.org/html/draft-ietf-netconf-nmda-restconf-00./* > > */ /* > > */We have a list of leafref values because in this example model, each tunnel > contains a list of paths, each of them contains a leafref. The get returns > a value for each instance of such a leafref, > which (as a string value) will be used as a constraint (foreign key) to > retrieve the instance of an explicit-path in the model above./* > > > > JFYI, in case there is some fundamental misunderstanding here: a leaf of > type leafref has a single value - *one* of those that satisfy the leafref > constraint, in case there are multiple "candidates". > > --Per > >> The client needs to issue at >> least one more get operation to retrieve the path information about the >> given tunnel. The request is to combine these two operations into one. >> >> In the RDBMS SQL world, join can be used when SQL select is performed, but >> NETCONF/YANG currently does not have this capability. >> >> Wed like to ask whether such a request is considered reasonable. >> >> If the request is reasonable, the next question is how to proceed. This >> seems to be a protocol issue rather than YANG modeling issue. Is it >> acceptable to add a new operation to achieve such a >> <get-data> operation with expanded leafrefs? >> >> Comments and suggestions are appreciated. >> >> Thanks, >> >> - Xufeng >> >> >> >> _______________________________________________ >> netmod mailing list >> [email protected] <mailto:[email protected]> >> https://www.ietf.org/mailman/listinfo/netmod >> > > _______________________________________________ > Netconf mailing list > [email protected] <mailto:[email protected]> > https://www.ietf.org/mailman/listinfo/netconf > _______________________________________________ netmod mailing list [email protected] https://www.ietf.org/mailman/listinfo/netmod
