Thank you both. It helps to know that "_version"_ is for, I would say succinctly, "NRT replication". I mean; that deserves to be said internally in some places! Might it be advantageous to imagine it being optional for non-NRT replicas? I'm not sure if it saves anything or reduces complexity anywhere. Related question: Is the VersionInfo (with its striped VersionBucket locks) related to this -- is it a vestige of "_version_" or is it for something else? If it isn't for something else, then I could imagine it being omitted for non-NRT; maybe a dummy implementation. BTW Bruno opened an issue/PR on it yesterday -- https://issues.apache.org/jira/browse/SOLR-17036
~ David On Wed, Oct 18, 2023 at 1:41 AM Ishan Chattopadhyaya < ichattopadhy...@gmail.com> wrote: > Fyi, SOLR-5944, is unreadable, but introduced the concept of previous > version or something like that. > > On Wed, 18 Oct, 2023, 10:35 am Mark Miller, <markrmil...@gmail.com> wrote: > > > The primary reason is as Ishan says - so that update reorders from leader > > to replica can be handled in both normal and failure cases. > > > > It’s also true that a part of the reason that the per document, NRT > design, > > with versions, was chosen was a desire to support per document optimistic > > concurrency. > > > > On Tue, Oct 17, 2023 at 11:37 PM Ishan Chattopadhyaya < > > ichattopadhy...@gmail.com> wrote: > > > > > Also DBQs use the version field to ensure they are applied correctly, > > even > > > if a DBQ is reordered > > > > > > On Wed, 18 Oct, 2023, 10:05 am Ishan Chattopadhyaya, < > > > ichattopadhy...@gmail.com> wrote: > > > > > > > To ensure reordered updates are processed properly from leader to > other > > > > replicas in NRT replication mode. > > > > > > > > On Wed, 18 Oct, 2023, 9:55 am David Smiley, <dsmi...@apache.org> > > wrote: > > > > > > > >> Question: Does the _version_ field have a purpose other than for > > "atomic > > > >> updates"? > > > >> I know SolrCloud and/or having an UpdateLog insists on it. But I > > don't > > > >> know if it's for that feature alone, or for additional non-obvious > > > >> internal > > > >> workings of SolrCloud. Mostly I'm just asking to have a deeper > > > >> understanding; the field doesn't bother me. If someone knows of any > > > docs > > > >> on it or old interesting JIRAs to read, I'd appreciate it. > > > >> > > > >> ~ David Smiley > > > >> Apache Lucene/Solr Search Developer > > > >> http://www.linkedin.com/in/davidwsmiley > > > >> > > > > > > > > > >
