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https://issues.apache.org/jira/browse/PHOENIX-153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16071041#comment-16071041
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Lars Hofhansl commented on PHOENIX-153:
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The default guidepost width is 300MB. Maybe we could go down to 10MB, once we
have guidepost combining.
Less than that will be a huge management burden to the system.
Still a good thing to do! On small tables you do not need to sample in the
first place, and for large tables - where it matters - we'll have sufficiently
many guide posts. (A 1TB table has over 3000 300MB guideposts, i.e. you'll have
a resolution of 0.03%, which is plenty good!)
> Implement TABLESAMPLE clause
> ----------------------------
>
> Key: PHOENIX-153
> URL: https://issues.apache.org/jira/browse/PHOENIX-153
> Project: Phoenix
> Issue Type: Task
> Reporter: James Taylor
> Assignee: Ethan Wang
> Labels: enhancement
> Attachments: Sampling_Accuracy_Performance.jpg
>
>
> Support the standard SQL TABLESAMPLE clause by implementing a filter that
> uses a skip next hint based on the region boundaries of the table to only
> return n rows per region.
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