--- slug: /en/sql-reference/table-functions/hdfs sidebar_position: 80 sidebar_label: hdfs --- # hdfs Creates a table from files in HDFS. This table function is similar to [url](../../sql-reference/table-functions/url.md) and [file](../../sql-reference/table-functions/file.md) ones. ``` sql hdfs(URI, format, structure) ``` **Input parameters** - `URI` — The relative URI to the file in HDFS. Path to file support following globs in readonly mode: `*`, `?`, `{abc,def}` and `{N..M}` where `N`, `M` — numbers, \``'abc', 'def'` — strings. - `format` — The [format](../../interfaces/formats.md#formats) of the file. - `structure` — Structure of the table. Format `'column1_name column1_type, column2_name column2_type, ...'`. **Returned value** A table with the specified structure for reading or writing data in the specified file. **Example** Table from `hdfs://hdfs1:9000/test` and selection of the first two rows from it: ``` sql SELECT * FROM hdfs('hdfs://hdfs1:9000/test', 'TSV', 'column1 UInt32, column2 UInt32, column3 UInt32') LIMIT 2 ``` ``` text ┌─column1─┬─column2─┬─column3─┐ │ 1 │ 2 │ 3 │ │ 3 │ 2 │ 1 │ └─────────┴─────────┴─────────┘ ``` ## Globs in path {#globs_in_path} Paths may use globbing. Files must match the whole path pattern, not only the suffix or prefix. - `*` — Represents arbitrarily many characters except `/` but including the empty string. - `?` — Represents an arbitrary single character. - `{some_string,another_string,yet_another_one}` — Substitutes any of strings `'some_string', 'another_string', 'yet_another_one'`. The strings can contain the `/` symbol. - `{N..M}` — Represents any number `>= N` and `<= M`. Constructions with `{}` are similar to the [remote](remote.md) and [file](file.md) table functions. **Example** 1. Suppose that we have several files with following URIs on HDFS: - ‘hdfs://hdfs1:9000/some_dir/some_file_1’ - ‘hdfs://hdfs1:9000/some_dir/some_file_2’ - ‘hdfs://hdfs1:9000/some_dir/some_file_3’ - ‘hdfs://hdfs1:9000/another_dir/some_file_1’ - ‘hdfs://hdfs1:9000/another_dir/some_file_2’ - ‘hdfs://hdfs1:9000/another_dir/some_file_3’ 2. Query the amount of rows in these files: ``` sql SELECT count(*) FROM hdfs('hdfs://hdfs1:9000/{some,another}_dir/some_file_{1..3}', 'TSV', 'name String, value UInt32') ``` 3. Query the amount of rows in all files of these two directories: ``` sql SELECT count(*) FROM hdfs('hdfs://hdfs1:9000/{some,another}_dir/*', 'TSV', 'name String, value UInt32') ``` :::note If your listing of files contains number ranges with leading zeros, use the construction with braces for each digit separately or use `?`. ::: **Example** Query the data from files named `file000`, `file001`, ... , `file999`: ``` sql SELECT count(*) FROM hdfs('hdfs://hdfs1:9000/big_dir/file{0..9}{0..9}{0..9}', 'CSV', 'name String, value UInt32') ``` ## Virtual Columns - `_path` — Path to the file. Type: `LowCardinalty(String)`. - `_file` — Name of the file. Type: `LowCardinalty(String)`. - `_size` — Size of the file in bytes. Type: `Nullable(UInt64)`. If the size is unknown, the value is `NULL`. ## Storage Settings {#storage-settings} - [hdfs_truncate_on_insert](/docs/en/operations/settings/settings.md#hdfs_truncate_on_insert) - allows to truncate file before insert into it. Disabled by default. - [hdfs_create_multiple_files](/docs/en/operations/settings/settings.md#hdfs_allow_create_multiple_files) - allows to create a new file on each insert if format has suffix. Disabled by default. - [hdfs_skip_empty_files](/docs/en/operations/settings/settings.md#hdfs_skip_empty_files) - allows to skip empty files while reading. Disabled by default. - [ignore_access_denied_multidirectory_globs](/docs/en/operations/settings/settings.md#ignore_access_denied_multidirectory_globs) - allows to ignore permission denied errors for multi-directory globs. **See Also** - [Virtual columns](../../engines/table-engines/index.md#table_engines-virtual_columns)