> On 29 Mar 2017, at 07:43, Bogaert, Bart (Nokia - BE/Antwerp) > <bart.boga...@nokia.com> wrote: > > Lada, thanks for the feedback. > > Any specific reason why you say that this would be more efficient when used > in the context of the parent container and not in the grouping?
As I wrote, the expression is evaluated once for each entry, always with the same result. It may or may not be a problem depending on the number of entries. Lada > > Regards, Bart > > -----Original Message----- > From: Ladislav Lhotka [mailto:lho...@nic.cz] > Sent: 29 March 2017 14:37 > To: Bogaert, Bart (Nokia - BE/Antwerp) <bart.boga...@nokia.com>; Bogaert, > Bart (Nokia - BE/Antwerp) <bart.boga...@nokia.com>; netmod@ietf.org > Subject: Re: [netmod] Question about must statement in grouping > > "Bogaert, Bart (Nokia - BE/Antwerp)" <bart.boga...@nokia.com> writes: > >> Changing "count(.) != 1" into "count(../a-list) != 1" in the grouping >> does the job as expected. So it seems that count(.) within the >> context of the a-list applies to each element in the list and rather >> than to the list itself? > > Both versions of the XPath expression are evaluated once for each entry of > the list, and the entry's 'a-list' node is the context node. By definition, > '.' selects the context node, so 'count(.)' is always 1. After the change, > '..' selects the parent node and 'a-list' then selects all nodes of that > name, which are the entries of the list. > > Note that it would be more efficient to verify the constraint on the parent > container, with 'count(a-list) != 1'. > > Lada > >> >> >> >> Regards, Bart >> >> >> >> From: netmod [mailto:netmod-boun...@ietf.org] On Behalf Of Bogaert, >> Bart (Nokia - BE/Antwerp) >> Sent: 29 March 2017 12:47 >> To: netmod@ietf.org >> Subject: [netmod] Question about must statement in grouping >> >> >> >> Hi, >> >> >> >> We have a question on the usage of a must statement within a grouping. >> >> >> >> Assume the following grouping >> >> >> >> grouping a-group { >> >> list a-list { >> >> must "count(.) != 1" { >> >> description >> >> "This list must either be empty or have at least 2 elements"; >> >> } >> >> key "entry"; >> >> leaf entry { >> >> type uint16; >> >> } >> >> leaf another-entry { >> >> type uint32; >> >> } >> >> } >> >> } >> >> >> >> And used in another module >> >> >> >> container a-container { >> >> uses a-group; >> >> } >> >> >> >> The uses actually results in a data-tree like below >> >> >> >> +--rw a-container >> >> +--rw a-list* [entry] >> >> +--rw entry uint16 >> >> +--rw another-entry uint32 >> >> >> >> Does the usage of the grouping usage also result in the expected >> behavior for the must statement when configuring /a-container/a-list? >> The '.' in the must statement in the grouping refers to 'a-list' so >> will that return 2 in case we have configured 2 elements in >> /a-container/a-list or should we write the must statement at the level >> of 'a-container' stating that "count(a-list) != 1" (as below)? >> >> >> >> grouping a-group { >> >> list a-list { >> >> key "entry"; >> >> leaf entry { >> >> type uint16; >> >> } >> >> } >> >> } >> >> >> >> And used in another module >> >> >> >> container a-container { >> >> uses a-group; >> >> must "count(a-list) != 1" { >> >> description >> >> "This list must either be empty or have at least 2 elements"; >> >> } >> >> } >> >> >> >> Best regards - Vriendelijke groeten, >> >> Bart Bogaert >> >> _______________________________________________ >> netmod mailing list >> netmod@ietf.org >> https://www.ietf.org/mailman/listinfo/netmod > > -- > Ladislav Lhotka, CZ.NIC Labs > PGP Key ID: 0xB8F92B08A9F76C67 -- Ladislav Lhotka, CZ.NIC Labs PGP Key ID: 0xB8F92B08A9F76C67 _______________________________________________ netmod mailing list netmod@ietf.org https://www.ietf.org/mailman/listinfo/netmod
