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https://issues.apache.org/jira/browse/PHOENIX-2143?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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James Taylor updated PHOENIX-2143:
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Summary: Use guidepost bytes instead of region name in stats primary key
(was: Use region start key instead of region name in stats primary key)
> Use guidepost bytes instead of region name in stats primary key
> ---------------------------------------------------------------
>
> Key: PHOENIX-2143
> URL: https://issues.apache.org/jira/browse/PHOENIX-2143
> Project: Phoenix
> Issue Type: Sub-task
> Reporter: James Taylor
>
> Our current SYSTEM.STATS table uses the region name as the last column in the
> primary key constraint. Instead, we should use the MIN_KEY column (which
> corresponds to the region start key). The advantage would be that the stats
> would then be ordered by region start key allowing us to approximate the
> number of guideposts which would be traversed given the start/stop row of a
> scan:
> {code}
> SELECT SUM(guide_posts_count) FROM SYSTEM.STATS WHERE min_key > :1 AND
> min_key < :2
> {code}
> where :1 is the start row and :2 is the stop row of the scan. With an UNNEST
> operator for ARRAYs, we could get a better approximation.
> As part of the upgrade to the new Phoenix version containing this fix, stats
> could simply be dropped and they'd be recalculated with the new schema.
> An alternative, even more granular approach would be to *not* use arrays to
> store the guide posts, but instead store them as individual rows with a
> schema like this.
> |PHYSICAL_NAME|VARCHAR|
> |COLUMN_FAMILY|VARCHAR|
> |GUIDE_POST_KEY|VARBINARY|
> |GUIDE_POST_WIDTH|LONG|
> In this alternative, the maintenance during compaction is higher, though, as
> you'd need to run a separate query to do the deletion of the old guideposts,
> followed by a commit of the new guideposts. The other disadvantage (besides
> requiring multiple queries) is that this couldn't be done transactionally.
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