a75dc80a76
### What changes were proposed in this pull request? Remove the unneeded embedded inline HTML markup by using the basic markdown syntax. Please see #28414 ### Why are the changes needed? Make the doc cleaner and easily editable by MD editors. ### Does this PR introduce _any_ user-facing change? No ### How was this patch tested? Manually build and check Closes #28451 from huaxingao/html_cleanup. Authored-by: Huaxin Gao <huaxing@us.ibm.com> Signed-off-by: Sean Owen <srowen@gmail.com>
97 lines
3 KiB
Markdown
97 lines
3 KiB
Markdown
---
|
|
layout: global
|
|
title: DISTRIBUTE BY Clause
|
|
displayTitle: DISTRIBUTE BY Clause
|
|
license: |
|
|
Licensed to the Apache Software Foundation (ASF) under one or more
|
|
contributor license agreements. See the NOTICE file distributed with
|
|
this work for additional information regarding copyright ownership.
|
|
The ASF licenses this file to You under the Apache License, Version 2.0
|
|
(the "License"); you may not use this file except in compliance with
|
|
the License. You may obtain a copy of the License at
|
|
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
|
|
|
Unless required by applicable law or agreed to in writing, software
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
See the License for the specific language governing permissions and
|
|
limitations under the License.
|
|
---
|
|
|
|
### Description
|
|
|
|
The `DISTRIBUTE BY` clause is used to repartition the data based
|
|
on the input expressions. Unlike the [CLUSTER BY](sql-ref-syntax-qry-select-clusterby.html)
|
|
clause, this does not sort the data within each partition.
|
|
|
|
### Syntax
|
|
|
|
```sql
|
|
DISTRIBUTE BY { expression [ , ... ] }
|
|
```
|
|
|
|
### Parameters
|
|
|
|
* **expression**
|
|
|
|
Specifies combination of one or more values, operators and SQL functions that results in a value.
|
|
|
|
### Examples
|
|
|
|
```sql
|
|
CREATE TABLE person (name STRING, age INT);
|
|
INSERT INTO person 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;
|
|
+---+-------+
|
|
|age| name|
|
|
+---+-------+
|
|
| 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;
|
|
+---+-------+
|
|
|age| name|
|
|
+---+-------+
|
|
| 25|Zen Hui|
|
|
| 25| Mike A|
|
|
| 18| John A|
|
|
| 18| Anil B|
|
|
| 16|Shone S|
|
|
| 16| Jack N|
|
|
+---+-------+
|
|
```
|
|
|
|
### Related Statements
|
|
|
|
* [SELECT Main](sql-ref-syntax-qry-select.html)
|
|
* [WHERE Clause](sql-ref-syntax-qry-select-where.html)
|
|
* [GROUP BY Clause](sql-ref-syntax-qry-select-groupby.html)
|
|
* [HAVING Clause](sql-ref-syntax-qry-select-having.html)
|
|
* [ORDER BY Clause](sql-ref-syntax-qry-select-orderby.html)
|
|
* [SORT BY Clause](sql-ref-syntax-qry-select-sortby.html)
|
|
* [CLUSTER BY Clause](sql-ref-syntax-qry-select-clusterby.html)
|
|
* [LIMIT Clause](sql-ref-syntax-qry-select-limit.html)
|