[PHOENIX-153] Implement TABLESAMPLE clause

• Type: Task
• Status: Resolved
• Resolution: Fixed
• Fix Version/s: 4.12.0
• Labels: enhancement
• old issue number: 22
• Assignee: Ethan Wang
• Reporter: James Taylor
• Created: 10/Mar/14 23:46
• Updated: 20/Sep/18 17:58
• Resolved: 01/Aug/17 19:07

Description

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.

When TABLESAMPLE clause is used, Phoenix will sample (N) percent of the the hbase table with only O(M) run time complexity. (N is size of table, M is size of stats)

[Update]
Usage:
https://phoenix.apache.org/tablesample.html

Syntax of using table sampling:
select * from PERSON TABLESAMPLE(45);
select count( * ) from PERSON TABLESAMPLE (49) LIMIT 2

Source Code:
https://git-wip-us.apache.org/repos/asf?p=phoenix.git;a=commitdiff;h=5e33dc12bc088bd0008d89f0a5cd7d5c368efa25

Issue Links

• duplicates: PHOENIX-3294 Support approximate COUNT(*) by using stats.
• links to: GitHub Pull Request #262