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From "Yonik Seeley (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-3178) Versioning - optimistic locking
Date Thu, 19 Apr 2012 19:22:40 GMT

    [ https://issues.apache.org/jira/browse/SOLR-3178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13257703#comment-13257703
] 

Yonik Seeley commented on SOLR-3178:
------------------------------------

Are there any technical objections to this patch?

It really piggybacks on all of the SolrCloud work done to pass around and check versions,
so it's really small.
The API is as follows:
- If you provide a _version_ > 0 with an add or a delete, the update will fail with a 409
unless the provided _version_ matches exactly the latest in the index for the ID.
- If you provide a _version_ < 0 with an add or delete, the update will fail with a 409
if the ID exists in the index.

That's the whole scope of this patch, and I believe is compatible with the larger scope of
what Per will provide in the future.
                
> 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
>
>   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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