如何正确将TSV导入Athena？两类技术疑问咨询

Great questions! Let's break them down clearly for you:

1. Can I name columns as c1, c2... and set all to STRING type when my TSV has no column names? #

Absolutely! This is totally valid and a common approach for unlabeled tab-separated files. The LazySimpleSerDe doesn't care about the actual column names you define—it just maps the first field in each row to your first column definition, the second field to the second column, and so on in order.

Setting all columns to STRING is also a safe choice, especially if you're unsure about the underlying data types upfront. You can always cast columns to their appropriate types during queries, or even alter the table schema later if you confirm specific data types.

Here's an example of how your CREATE TABLE statement would look:

CREATE EXTERNAL TABLE unlabeled_tsv_data (
  c1 STRING,
  c2 STRING,
  c3 STRING,
  -- Add as many cN columns as you have fields in your TSV rows
)
ROW FORMAT DELIMITED
  FIELDS TERMINATED BY '\t'
  ESCAPED BY '\\'
  LINES TERMINATED BY '\n'
LOCATION 's3://your-bucket/path/to/tsv-files/';

Just make sure the number of cN columns matches the number of fields per row in your TSV files—otherwise, you might run into parsing errors or unexpected null values.

2. Why isn't the year partition column listed in the main column definitions? #

This is a core concept in Athena (built on Hive) called partitioning, and it's designed to optimize query performance and cost. Let's break it down:

• Partition columns are virtual columns—they don't exist in your actual TSV data files. Instead, their values are extracted directly from the directory structure of your S3 storage.
• For the PARTITIONED BY (year STRING) clause to work, your S3 data should be organized in a partitioned path format like this:

  s3://athena-examples-myregion/flight/tsv/year=2020/
  s3://athena-examples-myregion/flight/tsv/year=2021/
  s3://athena-examples-myregion/flight/tsv/year=2022/
  

• Athena automatically pulls the year value from the year=YYYY segment of the path and adds it as a column to your table. This lets you run targeted queries like SELECT * FROM flight_delays_tsv WHERE year = '2022' to scan only the data from that year's directory, which cuts down on query time and data scanning costs significantly.

The reason year isn't in the main column list is because it's not part of the row data—it's metadata derived from how you've organized your files in S3. After creating the table, you'll typically need to run MSCK REPAIR TABLE flight_delays_tsv; to tell Athena to discover all existing partitions in your S3 path.

内容的提问来源于stack exchange，提问作者Chicago1988