[SPARK-15867] Use bucket files for TABLESAMPLE BUCKET

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Incomplete
• Affects Version/s: 1.6.0, 2.0.0
• Component/s: SQL
• Labels: bulk-closed
• Assignee: Unassigned
• Reporter: Andrew Or
• Created: 10/Jun/16 07:43
• Updated: 08/Oct/19 05:41
• Resolved: 08/Oct/19 05:41

Description

SELECT * FROM boxes TABLESAMPLE (BUCKET 3 OUT OF 16)

In Hive, this would select the 3rd bucket out of every 16 buckets there are in the table. E.g. if the table was clustered by 32 buckets then this would sample the 3rd and the 19th bucket. (See https://cwiki.apache.org/confluence/display/Hive/LanguageManual+Sampling)

In Spark, however, we simply sample 3/16 of the number of input rows.

Either we don't support it in Spark or do it in a way that's consistent with Hive.