01cc852982
### What changes were proposed in this pull request? Change the link to the Scala API document. ``` $ git grep "#org.apache.spark.package" docs/_layouts/global.html: <li><a href="api/scala/index.html#org.apache.spark.package">Scala</a></li> docs/index.md:* [Spark Scala API (Scaladoc)](api/scala/index.html#org.apache.spark.package) docs/rdd-programming-guide.md:[Scala](api/scala/#org.apache.spark.package), [Java](api/java/), [Python](api/python/) and [R](api/R/). ``` ### Why are the changes needed? The home page link for Scala API document is incorrect after upgrade to 3.0 ### Does this PR introduce any user-facing change? Document UI change only. ### How was this patch tested? Local test, attach screenshots below: Before: ![image](https://user-images.githubusercontent.com/4833765/74335713-c2385300-4dd7-11ea-95d8-f5a3639d2578.png) After: ![image](https://user-images.githubusercontent.com/4833765/74335727-cbc1bb00-4dd7-11ea-89d9-4dcc1310e679.png) Closes #27549 from xuanyuanking/scala-doc. Authored-by: Yuanjian Li <xyliyuanjian@gmail.com> Signed-off-by: Sean Owen <srowen@gmail.com>
95 lines
3.1 KiB
Markdown
95 lines
3.1 KiB
Markdown
---
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layout: global
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title: DISTRIBUTE BY Clause
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displayTitle: DISTRIBUTE BY Clause
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license: |
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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---
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The <code>DISTRIBUTE BY</code> clause is used to repartition the data based
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on the input expressions. Unlike the [CLUSTER BY](sql-ref-syntax-qry-select-clusterby.html)
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clause, this does not sort the data within each partition.
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### Syntax
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{% highlight sql %}
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DISTRIBUTE BY { expression [ , ... ] }
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{% endhighlight %}
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### Parameters
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<dl>
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<dt><code><em>expression</em></code></dt>
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<dd>
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Specifies combination of one or more values, operators and SQL functions that results in a value.
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</dd>
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</dl>
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### Examples
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{% highlight sql %}
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CREATE TABLE person (name STRING, age INT);
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INSERT INTO person VALUES
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('Zen Hui', 25),
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('Anil B', 18),
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('Shone S', 16),
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('Mike A', 25),
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('John A', 18),
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('Jack N', 16);
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-- Reduce the number of shuffle partitions to 2 to illustrate the behavior of `DISTRIBUTE BY`.
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-- It's easier to see the clustering and sorting behavior with less number of partitions.
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SET spark.sql.shuffle.partitions = 2;
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-- Select the rows with no ordering. Please note that without any sort directive, the result
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-- of the query is not deterministic. It's included here to just contrast it with the
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-- behavior of `DISTRIBUTE BY`. The query below produces rows where age columns are not
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-- clustered together.
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SELECT age, name FROM person;
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+---+-------+
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|age|name |
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+---+-------+
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|16 |Shone S|
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|25 |Zen Hui|
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|16 |Jack N |
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|25 |Mike A |
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|18 |John A |
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|18 |Anil B |
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+---+-------+
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-- Produces rows clustered by age. Persons with same age are clustered together.
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-- Unlike `CLUSTER BY` clause, the rows are not sorted within a partition.
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SELECT age, name FROM person DISTRIBUTE BY age;
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+---+-------+
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|age|name |
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+---+-------+
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|25 |Zen Hui|
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|25 |Mike A |
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|18 |John A |
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|18 |Anil B |
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|16 |Shone S|
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|16 |Jack N |
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+---+-------+
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{% endhighlight %}
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### Related Clauses
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- [SELECT Main](sql-ref-syntax-qry-select.html)
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- [WHERE Clause](sql-ref-syntax-qry-select-where.html)
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- [GROUP BY Clause](sql-ref-syntax-qry-select-groupby.html)
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- [HAVING Clause](sql-ref-syntax-qry-select-having.html)
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- [ORDER BY Clause](sql-ref-syntax-qry-select-orderby.html)
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- [SORT BY Clause](sql-ref-syntax-qry-select-sortby.html)
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- [CLUSTER BY Clause](sql-ref-syntax-qry-select-clusterby.html)
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- [LIMIT Clause](sql-ref-syntax-qry-select-limit.html)
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