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https://issues.apache.org/jira/browse/SOLR-3178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13263263#comment-13263263
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Yonik Seeley commented on SOLR-3178:
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Thanks for the patch Per!
I think I agree it would be nice to have more of the functionality consolidated
to the update handler and not do quite so much "up the callstack"... of course
the downside to this would be the context that the update processors have
(namely they know when a request, which can contain multiple updates, starts
and finishes).
Regardless - we are where we are right now... and doing the version check in
the update handler presents some problems. For cloud, we want to start sending
to replicas at the same time as indexing locally. We also want to check the
version before sending to replicas since it would be easy to get into a
scenario where a conditional update fails on some replicas and succeeds on
others (due to the fact that updates can easily be seen by different replicas
in a different order).
So I think the best way forward is to commit the patch that does the version
check in the distributed update processor, and then build off of that (for
instance your more nuanced error messages and the set/get requestVersion on the
update command).
> Versioning - optimistic locking
> -------------------------------
>
> Key: SOLR-3178
> URL: https://issues.apache.org/jira/browse/SOLR-3178
> Project: Solr
> Issue Type: New Feature
> Components: update
> Affects Versions: 3.5
> Environment: All
> Reporter: Per Steffensen
> Assignee: Per Steffensen
> Labels: RDBMS, insert, locking, nosql, optimistic, uniqueKey,
> update, versioning
> Fix For: 4.0
>
> Attachments: SOLR-3178.patch, SOLR_3173_3178_3382_plus.patch
>
> Original Estimate: 168h
> Remaining Estimate: 168h
>
> In order increase the ability of Solr to be used as a NoSql database (lots of
> concurrent inserts, updates, deletes and queries in the entire lifetime of
> the index) instead of just a search index (first: everything indexed (in one
> thread), after: only queries), I would like Solr to support versioning to be
> used for optimistic locking.
> When my intent (see SOLR-3173) is to update an existing document, I will need
> to provide a version-number equal to "the version number I got when I fetched
> the existing document for update" plus one. If this provided version-number
> does not correspond to "the newest version-number of that document at the
> time of update" plus one, I will get a VersionConflict error. If it does
> correspond the document will be updated with the new one, so that "the newest
> version-number of that document" is NOW one higher than before the update.
> Correct but efficient concurrency handling.
> When my intent (see SOLR-3173) is to insert a new document, the version
> number provided will not be used - instead a version-number 0 will be used.
> According to SOLR-3173 insert will only succeed if a document with the same
> value on uniqueKey-field does not already exist.
> In general when talking about different versions of "the same document", of
> course we need to be able to identify when a document "is the same" - that,
> per definition, is when the values of the uniqueKey-fields are equal.
> The functionality provided by this issue is only really meaningfull when you
> run with "updateLog" activated.
> This issue might be solved more or less at the same time as SOLR-3173, and
> only one single SVN patch might be given to cover both issues.
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