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https://issues.apache.org/jira/browse/PHOENIX-4051?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16104455#comment-16104455
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James Taylor commented on PHOENIX-4051:
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Looks like this quick patch didn't solve the issue that [~mujtabachohan] found
based on his testing. Mujtaba - if you could show the index rows generated for
a data row when there are more than one index rows generated, that would be
useful (including the data row updates too).
Rather than commit this, I think it'd be better to focus on PHOENIX-4052.
> Prevent out-of-order updates for mutable index updates
> ------------------------------------------------------
>
> Key: PHOENIX-4051
> URL: https://issues.apache.org/jira/browse/PHOENIX-4051
> Project: Phoenix
> Issue Type: Bug
> Reporter: James Taylor
> Assignee: James Taylor
> Attachments: PHOENIX-4051_v1.patch
>
>
> Out-of-order processing of data rows during index maintenance causes mutable
> indexes to become out of sync with regard to the data table. Here's a simple
> example to illustrate the issue:
> # Assume table T(K,V) and index X(V,K).
> # Upsert T(A, 1) at t10. Index updates: Put X(1,A) at t10.
> # Upsert T(A, 3) at t30. Index updates: Delete X(1,A) at t29, Put X(3,A) at
> t30.
> # Upsert T(A,2) at t20. Index updates: Delete X(1,A) at t19, Put X(2,A) at
> t20, Delete X(2,A) at t29
> Ideally, we'd want to remove the Delete X(1,A) at t29 since this isn't
> correct in terms of timeline consistency, but we can't do that with HBase
> without support for deleting/undoing Delete markers.
> The above is not what is occurring. Instead, when T(A,2) comes in, the Put
> X(2,A) will occur at t20, but the Delete won't occur. This causes more index
> rows than data rows, essentially making it invalid.
> A quick fix is to reset the timestamp of the data table mutations to the
> current time within the preBatchMutate call, when the row is exclusively
> locked. This skirts the issue because then timestamps won't overlap.
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