[jira] [Commented] (OAK-8002) RDBDocumentStore: MissingLastRevSeeker slow on DB2

["Julian Reschke (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-8002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16751137#comment-16751137 ] 

Julian Reschke commented on OAK-8002:
-------------------------------------

Potential fix: https://issues.apache.org/jira/secure/attachment/12956148/OAK-8002.diff

> RDBDocumentStore: MissingLastRevSeeker slow on DB2
> --------------------------------------------------
>
>                 Key: OAK-8002
>                 URL: https://issues.apache.org/jira/browse/OAK-8002
>             Project: Jackrabbit Oak
>          Issue Type: Technical task
>          Components: rdbmk
>            Reporter: Julian Reschke
>            Assignee: Julian Reschke
>            Priority: Minor
>             Fix For: 1.12
>
>         Attachments: OAK-8002.diff
>
>
> This is because the generic {{MissingLastRevSeeker}} gets candidate in batches (of 100), but in order to do batching, requires results to be sorted by ID.
> For DB2 we by default have indices on both ID and MODIFIED, but contrary to our expection a query that involves both indices does not perforn well. Adding a compound index on ID *and* MODIFIED improves performance, but I'm hesitant to add this just to improve a recovery job.
> A more logical approach would be not to require batching/sorting by adopting the approach in {{MongoMissingLastRevSeeker}} which doesn't require sorting by ID in the first place.



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