LingXiao Lan created HIVE-18049:
-----------------------------------
Summary: Enable Hive on Tez to provide globally sorted clustered
table
Key: HIVE-18049
URL: https://issues.apache.org/jira/browse/HIVE-18049
Project: Hive
Issue Type: Improvement
Components: Hive, Tez
Reporter: LingXiao Lan
Fix For: 2.1.1
CREATE TABLE `test`(
`time` int,
`userid` bigint)
CLUSTERED BY (
userid)
SORTED BY (
userid ASC)
INTO 4 BUCKETS
;
When insert data into this table, the data will be sorted into 4 buckets
automatically. But because hive uses hash partitioner by default, the data is
only sorted in each bucket and isn't sorted among different buckets. Sometimes
we need the data to be globally sorted, to optimizing indexing, for example.
If we can sample the table first and use TotalOrderPartitioner, this work could
be done. The difficulty is how do we automatically decide when to use
TotalOrderPartitioner and when not, because a insertion query can be complex,
which results in a complex DAG in Tez.
I have implemented a temporary version. It uses a customer partitioner which
combines hash partitioner and totalorder partitioner. A physical optimizer is
added to hive to decide to choose which partitioner. But in order to reduce the
work load, this version should affect tez source code, which is not necessary
in fact.
I'm wondering if we can implement a more common version which addresses this
issue.
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