通过

DISTRIBUTE BY 子句

  • 项目

适用于：勾选“是” Databricks SQL 勾选“是” Databricks Runtime

根据输入表达式对数据进行重新分区。 与 CLUSTER BY 子句不同，不会对每个分区中的数据进行排序。

语法

DISTRIBUTE BY expression [, ...]

参数

示例

> CREATE TEMP VIEW person (name, age)
  AS VALUES ('Zen Hui', 25),
            ('Anil B', 18),
            ('Shone S', 16),
            ('Mike A', 25),
            ('John A', 18),
            ('Jack N', 16);

-- Reduce the number of shuffle partitions to 2 to illustrate the behavior of `DISTRIBUTE BY`.
-- It's easier to see the clustering and sorting behavior with less number of partitions.
> SET spark.sql.shuffle.partitions = 2;

-- Select the rows with no ordering. Please note that without any sort directive, the result
-- of the query is not deterministic. It's included here to just contrast it with the
-- behavior of `DISTRIBUTE BY`. The query below produces rows where age columns are not
-- clustered together.
> SELECT age, name FROM person;
  16 Shone S
  25 Zen Hui
  16  Jack N
  25  Mike A
  18  John A
  18  Anil B

-- Produces rows clustered by age. Persons with same age are clustered together.
-- Unlike `CLUSTER BY` clause, the rows are not sorted within a partition.
> SELECT age, name FROM person DISTRIBUTE BY age;
  25 Zen Hui
  25  Mike A
  18  John A
  18  Anil B
  16 Shone S
  16  Jack N