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spark-sql-columns-and-dataset-operators.html
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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
<title>Apache Spark™ Workshop | Spark SQL | Columns and Dataset Operators</title>
<meta name="description" content="Apache Spark™ Workshop | Spark SQL | Columns and Dataset Operators">
<meta name="author" content="Jacek Laskowski">
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<div class="footer">
<footer style="font-size: small;">
© <a href="https://medium.com/@jaceklaskowski">Jacek Laskowski</a> 2022 / <a
href="https://twitter.com/jaceklaskowski">@JacekLaskowski</a>
</footer>
</div>
<div class="slides">
<section class="intro" data-transition="zoom" id="home">
<p>
<img width="17%" style="background:none; border:none; box-shadow:none;" data-src="images/spark-logo.png">
<img width="10%" src="images/jacek_laskowski_20201229_200x200.png" style="border: 0">
</p>
<h1 style="font-size: 2.99em;">Columns and Dataset Operators</h1>
<h3>Apache Spark 3.2 / Spark SQL</h3>
<hr>
<h4 style="font-size: smaller;">
<a href="https://twitter.com/jaceklaskowski">@jaceklaskowski</a> / <a
href="https://stackoverflow.com/users/1305344/jacek-laskowski">StackOverflow</a> / <a
href="https://github.com/jaceklaskowski">GitHub</a> / <a
href="https://www.linkedin.com/in/jaceklaskowski/">LinkedIn</a>
<br>
The "Internals" Books: <a href="https://books.japila.pl">books.japila.pl</a>
</h4>
</section>
<section id="agenda" data-markdown>
<textarea data-template>
<!-- .slide: style="font-size: 90%" -->
## Agenda
1. [Columns](#/columns)
1. [Column Operators / Expressions](#/column-operators)
1. [Dataset Operators](#/dataset-operators)
</textarea>
</section>
<section id="columns" data-markdown>
<textarea data-template>
<!-- .slide: style="font-size: 90%" -->
## Columns
1. **Column** is a function that generates a value per row
* Internally, a Catalyst expression with `eval` method
1. **Column** type with methods
* _Explained in the following slide_
1. Columns can be <b>free</b> or <b>bound</b> (associated or not with Datasets)
```scala
$"columnName" // free (no Dataset) column reference
myDataset("id") // bound column reference
```
1. Use **import spark.implicits._**
1. Switch to [The Internals of Spark SQL](https://books.japila.pl/spark-sql-internals/)
* [Column](https://books.japila.pl/spark-sql-internals/Column/)
</textarea>
</section>
<section id="column-operators" data-markdown>
<textarea data-template>
<!-- .slide: style="font-size: 90%" -->
## Column Operators / Expressions
1. Special **★** (star) column reference
1. **Operators** to create (compound) columns
* **as**, **alias** or **name** for aliases
* **===** for equality _(!)_
* **desc**, **desc_nulls_first** and **desc_nulls_last** (and for **asc**)
* **getItem** to access items in arrays and maps
* **over** for windowed aggregates
* **cast** for casting to a custom data type
* **when** and **otherwise** for conditional values
1. Home exercise
* Read up [Column's scaladoc](http://spark.apache.org/docs/latest/api/scala/org/apache/spark/sql/Column.html)
</textarea>
</section>
<section>
<section id="dataset-operators" data-markdown>
<textarea data-template>
<!-- .slide: style="font-size: 90%" -->
## Dataset Operators
1. **Dataset Operators** work with all records of a Dataset
* **as** to converting a Row-based DataFrame to a Dataset
* **createOrReplaceTempView** to register a temporary view
* **explain** to show the logical and execution plans
* **flatMap** to "explode" records
* **randomSplit** to split records to two Datasets randomly
* **select**, **selectExpr**, **filter**, **where**
* … _many many more_ — read up [Dataset's scaladoc](http://spark.apache.org/docs/latest/api/scala/org/apache/spark/sql/Dataset.html)
1. Switch to [The Internals of Spark SQL](https://books.japila.pl/spark-sql-internals/)
* [Dataset](https://books.japila.pl/spark-sql-internals/Dataset/)
</textarea>
</section>
</section>
<section id="recap" data-markdown>
<textarea data-template>
<!-- .slide: style="font-size: 90%" -->
## Recap
1. [Columns](#/columns)
1. [Column Operators / Expressions](#/column-operators)
1. [Dataset Operators](#/dataset-operators)
</textarea>
</section>
<section style="text-align: left" data-markdown id="questions">
<textarea data-template>
# Questions?
* Read [The Internals of Apache Spark](https://books.japila.pl/apache-spark-internals/)
* Read [The Internals of Spark SQL](https://books.japila.pl/spark-sql-internals/)
* Read [The Internals of Spark Structured Streaming](https://books.japila.pl/spark-structured-streaming-internals/)
* Follow [@jaceklaskowski](https://twitter.com/jaceklaskowski) on twitter
* Upvote [my questions and answers on StackOverflow](http://stackoverflow.com/users/1305344/jacek-laskowski)
</textarea>
</section>
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