S3 

This engine provides integration with Amazon S3 ecosystem. This engine is similar
to the HDFS engine, but provides S3-specific features.

Usage 

ENGINE = S3(path, [aws_access_key_id, aws_secret_access_key,] format, structure, [compression])

Input parameters

  • path — Bucket url with path to file. Supports following wildcards in readonly mode: *, ?, {abc,def} and {N..M} where N, M — numbers, `’abc’, ‘def’ — strings.
  • format — The format of the file.
  • structure — Structure of the table. Format 'column1_name column1_type, column2_name column2_type, ...'.
  • compression — Parameter is optional. Supported values: none, gzip/gz, brotli/br, xz/LZMA, zstd/zst. By default, it will autodetect compression by file extension.

Example:

1. Set up the s3_engine_table table:

CREATE TABLE s3_engine_table (name String, value UInt32) ENGINE=S3('https://storage.yandexcloud.net/my-test-bucket-768/test-data.csv.gz', 'CSV', 'name String, value UInt32', 'gzip')

2. Fill file:

INSERT INTO s3_engine_table VALUES ('one', 1), ('two', 2), ('three', 3)

3. Query the data:

SELECT * FROM s3_engine_table LIMIT 2
┌─name─┬─value─┐
│ one  │     1 │
│ two  │     2 │
└──────┴───────┘

Implementation Details 

  • Reads and writes can be parallel
  • Not supported:
    • ALTER and SELECT...SAMPLE operations.
    • Indexes.
    • Replication.

Globs in path

Multiple path components can have globs. For being processed file should exist and match to the whole path pattern. Listing of files determines during SELECT (not at CREATE moment).

  • * — Substitutes any number of any characters except / including empty string.
  • ? — Substitutes any single character.
  • {some_string,another_string,yet_another_one} — Substitutes any of strings 'some_string', 'another_string', 'yet_another_one'.
  • {N..M} — Substitutes any number in range from N to M including both borders. N and M can have leading zeroes e.g. 000..078.

Constructions with {} are similar to the remote table function.

Example

  1. Suppose we have several files in TSV format with the following URIs on HDFS:
  1. There are several ways to make a table consisting of all six files:
CREATE TABLE table_with_range (name String, value UInt32) ENGINE = S3('https://storage.yandexcloud.net/my-test-bucket-768/{some,another}_prefix/some_file_{1..3}', 'CSV')
  1. Another way:
CREATE TABLE table_with_question_mark (name String, value UInt32) ENGINE = S3('https://storage.yandexcloud.net/my-test-bucket-768/{some,another}_prefix/some_file_?', 'CSV')
  1. Table consists of all the files in both directories (all files should satisfy format and schema described in query):
CREATE TABLE table_with_asterisk (name String, value UInt32) ENGINE = S3('https://storage.yandexcloud.net/my-test-bucket-768/{some,another}_prefix/*', 'CSV')

Example

Create table with files named file-000.csv, file-001.csv, … , file-999.csv:

CREATE TABLE big_table (name String, value UInt32) ENGINE = S3('https://storage.yandexcloud.net/my-test-bucket-768/big_prefix/file-{000..999}.csv', 'CSV')

Virtual Columns 

  • _path — Path to the file.
  • _file — Name of the file.

S3-related settings 

The following settings can be set before query execution or placed into configuration file.

  • s3_max_single_part_upload_size — Default value is 64Mb. The maximum size of object to upload using singlepart upload to S3.
  • s3_min_upload_part_size — Default value is 512Mb. The minimum size of part to upload during multipart upload to S3 Multipart upload.
  • s3_max_redirects — Default value is 10. Max number of S3 redirects hops allowed.

Security consideration: if malicious user can specify arbitrary S3 URLs, s3_max_redirects must be set to zero to avoid SSRF attacks; or alternatively, remote_host_filter must be specified in server configuration.

See Also

Original article

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