HDFS

Name

hdfs

Description

HDFS table-valued-function(tvf), allows users to read and access file contents on S3-compatible object storage, just like accessing relational table. Currently supports csv/csv_with_names/csv_with_names_and_types/json/parquet/orc file format.

grammer

1. hdfs(
2. "uri" = "..",
3. "fs.defaultFS" = "...",
4. "hadoop.username" = "...",
5. "format" = "csv",
6. "keyn" = "valuen"
7. ...
8. );

parameter description

Related parameters for accessing hdfs:

• uri: (required) hdfs uri.
• fs.defaultFS: (required)
• hadoop.username: (required) Can be any string, but cannot be empty.
• hadoop.security.authentication: (optional)
• hadoop.username: (optional)
• hadoop.kerberos.principal: (optional)
• hadoop.kerberos.keytab: (optional)
• dfs.client.read.shortcircuit: (optional)
• dfs.domain.socket.path: (optional)

File format parameters:

• format: (required) Currently support csv/csv_with_names/csv_with_names_and_types/json/parquet/orc
• column_separator: (optional) default ,.
• line_delimiter: (optional) default \n.

The following 6 parameters are used for loading in json format. For specific usage methods, please refer to: Json Load - read_json_by_line: (optional) default "true" - strip_outer_array: (optional) default "false" - json_root: (optional) default "" - json_paths: (optional) default "" - num_as_string: (optional) default false - fuzzy_parse: (optional) default false

Examples

Read and access csv format files on hdfs storage.

1. MySQL [(none)]> select * from hdfs(
2. "uri" = "hdfs://127.0.0.1:842/user/doris/csv_format_test/student.csv",
3. "fs.defaultFS" = "hdfs://127.0.0.1:8424",
4. "hadoop.username" = "doris",
5. "format" = "csv");
6. +------+---------+------+
7. | c1   | c2      | c3   |
8. +------+---------+------+
9. | 1    | alice   | 18   |
10. | 2    | bob     | 20   |
11. | 3    | jack    | 24   |
12. | 4    | jackson | 19   |
13. | 5    | liming  | 18   |
14. +------+---------+------+

Can be used with desc function :

1. MySQL [(none)]> desc function hdfs(
2. "uri" = "hdfs://127.0.0.1:8424/user/doris/csv_format_test/student_with_names.csv",
3. "fs.defaultFS" = "hdfs://127.0.0.1:8424",
4. "hadoop.username" = "doris",
5. "format" = "csv_with_names");

Keywords

1. hdfs, table-valued-function, tvf

Best Practice

For more detailed usage of HDFS tvf, please refer to S3 tvf, The only difference between them is the way of accessing the storage system.