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https://issues.apache.org/jira/browse/PHOENIX-3623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16490880#comment-16490880
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James Taylor commented on PHOENIX-3623:
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Our [storage format|https://phoenix.apache.org/columnencoding.html] that is
used by default in Phoenix won't work well out-of-the-box with Omid. In the
mutable case, it expects that the column qualifier can be used as the position
in the List<Cell> used by HBase, and in the immutable case, it expects a single
Cell to be used in which all values are stored.
We can try to support these storage formats in the future, but for now I can
disable them when we use Omid transactions. That should help reduce the
failures substantially.
> Integrate Omid with Phoenix
> ---------------------------
>
> Key: PHOENIX-3623
> URL: https://issues.apache.org/jira/browse/PHOENIX-3623
> Project: Phoenix
> Issue Type: New Feature
> Reporter: Ohad Shacham
> Assignee: Ohad Shacham
> Priority: Major
>
> The purpose of this Jira is to propose a work plan for connecting Omid to
> Phoenix.
> Each task of the following will be handled in a seperate sub Jira. Subtasks
> 4.* are related to augmenting Omid to support features required by Phoenix
> and therefore, their corresponding Jiras will appear under Omid and not under
> Phoenix.
> Each task is completed by a commit.
> Task 1: Adding transaction abstraction layer (TAL) - Currently Tephra calls
> are integrated inside Phoenix code. Therefore, in order to support both Omid
> and Tephra, we need to add another abstraction layer that later-on will be
> connected to both Tephra and Omid. The first tasks is to define such an
> interface.
> Task 2: Implement TAL functionality for Tephra.
> Task 3: Refactor Phoenix to use TAL instead of direct calls to Tephra.
> Task 4: Implement Omid required features for Phoenix:
> Task 4.1: Add checkpoints to Omid. A checkpoint is a point in a transaction
> where every write occurs after the checkpoint is not visible by the
> transaction. Explanations for this feature can be seen in [TEPHRA-96].
> Task 4.2: Add an option to mark a key as non-conflicting. The motivation is
> to reduce the size of the write set needed by the transaction manager upon
> commit as well as reduce the conflict detection work.
> Task 4.3: Add support for transactions that never abort. Such transactions
> will only make other inflight transactions abort and will abort only in case
> of a transaction manager failure.
> These transactions are needed for ‘create index’ and the scenario was
> discussed in [TEPHRA-157] and [PHOENIX-2478]. Augmenting Omid with this kind
> of transactions was also discussed in [OMID-56].
> Task 4.4: Add support for returning multiple versions in a scan. The use case
> is described in [TEPHRA-134].
> Task 4.5: Change Omid's timestamp mechanism to return real time based
> timestamp, while keeping monotonicity.
> Task 5: Implement TAL functionality for Omid.
> Task 6: Implement performance tests and tune Omid for Phoenix use. This task
> requires understanding of common usage scenarios in Phoenix as well as
> defining the tradeoff between throughput and latency.
> Could you please review the proposed work plan?
> Also, could you please let me know whether I missed any augmentation needed
> for Omid in order to support Phoenix operations?
> I opened a jira [OMID-82] that encapsulates all Omid related development for
> Phoenix.
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