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https://issues.apache.org/jira/browse/PHOENIX-2565?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15802411#comment-15802411
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Samarth Jain commented on PHOENIX-2565:
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If we go by the bitset approach where we don't store offset for missing or null
columns, then figuring out where the bytes for a column are stored in the
packed cell would no longer be a O(1) operation. For finding every column, on
an average, we would have to go through half of the bitset to figure out the
bytes for a column. We could possibly optimize that though by caching the
bitset/offset information. This would come in handy especially when we have to
evaluate multiple ArrayColumnExpressions against the packed cell. The caching
would have to be done at a higher level though (parent of
ArrayColumnExpression?). The cache would be built when evaluating the first
ArrayColumnExpression. Subsequent evaluate() calls won't then have to compute
where the bytes are.
> 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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