[jira] [Updated] (PHOENIX-153) Implement TABLESAMPLE clause

["Ethan Wang (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/PHOENIX-153?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ethan Wang updated PHOENIX-153:
-------------------------------
    Attachment: Sampling_Accuracy_Performance.jpg

A chart that denotes the TABLESAMPLING's accuracy regarding sampled size vs expected size.

Note, 
1, The test environment is a single node, single region hbase cluster (1.3). Test table with random integer as PK, with about 400K rows.
2, The guide post width has been pre set as 10K and 200K, respectively
3, The consistent hashing algorithm used in TableSamplerPredicate (a.k.a, the dice, used to hashing scan.star_rowkey to decide if a guidepost is going to be selected), is used as FNV with LazyModMethod. 

> 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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