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## What Will You Learn?

- What is Amazon Athena?
- What are the basics of Amazon Athena?
- What are the use cases for Amazon Athena?
- How can I import data into Amazon Athena?
- Where can I learn more about Amazon Athena?

## The Basics

Learn Amazon Athena basics. Amazon Athena is meant for querying copious amounts of data. It's a straightforward service based on [Presto]. The Presto Foundation calls Amazon Athena and Amazon EMR [Presto Cloud on their website.]

It's [not cheap] to use Amazon Athena, but it is convenient. It costs $5.00 per TB of data scanned. It's possible to pay a third of that with compression. Additional savings occur when querying a single column. The golden feature of Athena is its scaled cluster of servers. Setting up your own [Presto] analytics engine would take more work.

### Primary Use Cases

- Querying vast amounts of
  - Log Data
  - Behavioral Data
  - Noncritical data

## Importing Data

I needed to query a 58G CSV file. I could load the ~1 billion rows into PostgreSQL, but any queries on the data caused my machine to crash. I wrote a Python script to query the data, which works but takes too long to process. So, I brought out the big guns.

I tried Athena as a solution. Here's how it went down.

I created this table to store my CSV file. This table holds the output of an AWS command-line query.

```sql
DROP TABLE learnamazonathena.s3_objects;
CREATE EXTERNAL TABLE IF NOT EXISTS learnamazonathena.s3_objects (
         time string,
         bytes bigint,
         object string
)
ROW FORMAT SERDE 'org.apache.hadoop.hive.serde2.OpenCSVSerde'
STORED AS TEXTFILE
LOCATION 's3://learn-amazon-athena/csv';
```

Amazon S3 is now the data store for the CSV file. I generated the CSV file with these commands.

```sh
# Query all S3 objects recursively
aws s3 ls --recursive learn-amazon-athena > s3_objects.csv

# Format the output as a CSV file
perl -p -i -e ';s/(^.{0,19})(\s+)([0-9]+)(\s)(.+)$/"\1","\3","\5"/g'; applications.csv
```

I ran this query against the newly created table.

```sql
SELECT split(object,
         ';/';), SUM(bytes)
FROM learnamazonathena.s3_objects
GROUP BY  split(object, ';/';)
```

This query took seventeen seconds to complete.

I love how fast and straightforward Amazon Athena is. The CSV file I created is small in the grand scheme of things. Facebook built Presto to query obscene amounts of data and later open-sourced it.

Go open source!

## Learn Amazon Athena - Beyond the Basics

- **Books**
  - [Getting Started - User Guide] — AWS
  - [Amazon Athena - User Guide] — AWS
  - [Athena FAQ] — AWS
- **Video**
  - [Amazon Web Services: Data Analytics]

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[Presto]: https://prestodb.io/
[presto cloud on their website.]: https://prestodb.io/resources.html#cloud
[not cheap]: https://aws.amazon.com/athena/pricing/
[getting started - user guide]: https://docs.aws.amazon.com/athena/latest/ug/getting-started.html
[amazon athena - user guide]: https://docs.aws.amazon.com/athena/latest/ug/athena-ug.pdf
[athena faq]: https://aws.amazon.com/athena/faqs/
[Amazon Web Services: Data Analytics]: https://aws.amazon.com/athena/getting-started/