[jira] [Commented] (OAK-4535) Analyze impact of Mongo isolation guarantees and Query result

["Marcel Reutegger (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-4535?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15996619#comment-15996619 ] 

Marcel Reutegger commented on OAK-4535:
---------------------------------------

It turns out we do have a problem with a query in Oak. See [discussion|https://lists.apache.org/thread.html/36ade745b7f6a0417aab578c21ca9fb072a7d6e5c43c724b85a153bf@%3Coak-dev.jackrabbit.apache.org%3E] on oak-dev. The class {{MongoMissingLastRevSeeker}} sorts on {{_modified}} descending, which means it is susceptible to the consistency behaviour described in [article|https://blog.meteor.com/mongodb-queries-dont-always-return-all-matching-documents-654b6594a827].

> Analyze impact of Mongo isolation guarantees and Query result
> -------------------------------------------------------------
>
>                 Key: OAK-4535
>                 URL: https://issues.apache.org/jira/browse/OAK-4535
>             Project: Jackrabbit Oak
>          Issue Type: Task
>          Components: mongomk
>            Reporter: Chetan Mehrotra
>            Assignee: Chetan Mehrotra
>
> As per [Mongo Isolation guarantees |https://docs.mongodb.com/manual/faq/concurrency/#what-isolation-guarantees-does-mongodb-provide]
> {quote}
> Reads may miss matching documents that are updated during the course of the read operation.
> {quote}
> This can result in some scenarios where query performed might miss out on some documents if that document gets modified while query is being execute.
> Aim of this task is to analyze the kind of queries current Oak uses with Mongo and see if current support from Mongo is sufficient for our needs



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