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https://issues.apache.org/jira/browse/PHOENIX-2565?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15799148#comment-15799148
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Samarth Jain commented on PHOENIX-2565:
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It only stores the start position-length information only for those columns
that have a value. This would provide us savings for sparse data unlike our
VARBINARY ARRAY scheme where we end up storing the OFFSET information even for
those columns that are not present in the packed cell. For dense data, I expect
this scheme to occupy slightly more space since we will be storing length and
start position instead of just offset. Would be interesting to see how this
would behave if we have snappy or some other compression on.
[~jamestaylor] - WDYT?
> Store data for immutable tables in single KeyValue
> --------------------------------------------------
>
> Key: PHOENIX-2565
> URL: https://issues.apache.org/jira/browse/PHOENIX-2565
> Project: Phoenix
> Issue Type: Improvement
> Reporter: James Taylor
> Assignee: Thomas D'Silva
> Attachments: PHOENIX-2565-v2.patch, PHOENIX-2565-wip.patch,
> PHOENIX-2565.patch
>
>
> Since an immutable table (i.e. declared with IMMUTABLE_ROWS=true) will never
> update a column value, it'd be more efficient to store all column values for
> a row in a single KeyValue. We could use the existing format we have for
> variable length arrays.
> For backward compatibility, we'd need to support the current mechanism. Also,
> you'd no longer be allowed to transition an existing table to/from being
> immutable. I think the best approach would be to introduce a new IMMUTABLE
> keyword and use it like this:
> {code}
> CREATE IMMUTABLE TABLE ...
> {code}
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