[jira] [Commented] (SOLR-5374) Support user configured doc-centric versioning rules

["Ramkumar Aiyengar (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-5374?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13801632#comment-13801632 ] 

Ramkumar Aiyengar commented on SOLR-5374:
-----------------------------------------

This feature certainly is helpful as is, but it might not always be practical in a distributed system to have a version ordering across updates as it's likely to involve a single point of coordination if you need one. In such cases, it might just suffice for the system if the versions were just equality comparable rather than having a strict ordering -- i.e. update if the previous version equals what I expect, else reject the update. In some sense, if some external coordinator is able to guarantee a version ordering amongst updates, couldn't the same system be able to order the queue of updates to Solr?

> Support user configured doc-centric versioning rules
> ----------------------------------------------------
>
>                 Key: SOLR-5374
>                 URL: https://issues.apache.org/jira/browse/SOLR-5374
>             Project: Solr
>          Issue Type: Improvement
>            Reporter: Hoss Man
>            Assignee: Hoss Man
>         Attachments: SOLR-5374.patch
>
>
> The existing optimistic concurrency features of Solr can be very handy for ensuring that you are only updating/replacing the version of the doc you think you are updating/replacing, w/o the risk of someone else adding/removing the doc in the mean time -- but I've recently encountered some situations where I really wanted to be able to let the client specify an arbitrary version, on a per document basis, (ie: generated by an external system, or perhaps a timestamp of when a file was last modified) and ensure that the corresponding document update was processed only if the "new" version is greater then the "old" version -- w/o needing to check exactly which version is currently in Solr.  (ie: If a client wants to index version 101 of a doc, that update should fail if version 102 is already in the index, but succeed if the currently indexed version is 99 -- w/o the client needing to ask Solr what the current version)
> The idea Yonik brought up in SOLR-5298 (letting the client specify a {{\_new\_version\_}} that would be used by the existing optimistic concurrency code to control the assignment of the {{\_version\_}} field for documents) looked like a good direction to go -- but after digging into the way {{\_version\_}} is used internally I realized it requires a uniqueness constraint across all update commands, that would make it impossible to allow multiple independent documents to have the same {{\_version\_}}.
> So instead I've tackled the problem in a different way, using an UpdateProcessor that is configured with user defined field to track a "DocBasedVersion" and uses the RTG logic to figure out if the update is allowed.



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