How S3 select pricing works? What is data returned and scanned in s3 select means

问题

I have a 1M rows of CSV data. select 10 rows, Will I be billed for 10 rows. What is data returned and data scanned means in S3 Select?

There is less documentation on these terms of S3 select

回答1:

To keep things simple lets forget for some time that S3 reads in a columnar way. Suppose you have the following data:

| City       | Last Updated Date   |
|------------|---------------------|
| London     | 1st Jan             |
| London     | 2nd Jan             |
| New Delhi  | 2nd Jan             |

A query for fetching the latest update date

• forces S3 to scan all 3 records
• but the returned records are only 2 (when the last updated date is 2nd Jan)

A query of select city where last updated date is 1st Jan,

• will scan all 3 rows
• but return only 1 string - "New Delhi".

Hence based on your query, it might scan more data (3 rows) but return less data (2 rows).

I hope you understand the difference between Data Scanned and Data Returned now.

来源：https://stackoverflow.com/questions/53001443/how-s3-select-pricing-works-what-is-data-returned-and-scanned-in-s3-select-mean