Jaa

DISTRIBUTE BY clause

  • Artikkeli

Applies to: check marked yes Databricks SQL check marked yes Databricks Runtime

Repartitions data based on the input expressions. Unlike the CLUSTER BY clause, does not sort the data within each partition.

Syntax

DISTRIBUTE BY expression [, ...]

Parameters

Examples

> 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