--- slug: /en/sql-reference/table-functions/file sidebar_position: 60 sidebar_label: file --- # file A table engine which provides a table-like interface to SELECT from and INSERT into files, similar to the [s3](/docs/en/sql-reference/table-functions/url.md) table function. Use `file()` when working with local files, and `s3()` when working with buckets in object storage such as S3, GCS, or MinIO. The `file` function can be used in `SELECT` and `INSERT` queries to read from or write to files. **Syntax** ``` sql file([path_to_archive ::] path [,format] [,structure] [,compression]) ``` **Parameters** - `path` — The relative path to the file from [user_files_path](/docs/en/operations/server-configuration-parameters/settings.md#server_configuration_parameters-user_files_path). Supports in read-only mode the following [globs](#globs_in_path): `*`, `?`, `{abc,def}` (with `'abc'` and `'def'` being strings) and `{N..M}` (with `N` and `M` being numbers). - `path_to_archive` - The relative path to a zip/tar/7z archive. Supports the same globs as `path`. - `format` — The [format](/docs/en/interfaces/formats.md#formats) of the file. - `structure` — Structure of the table. Format: `'column1_name column1_type, column2_name column2_type, ...'`. - `compression` — The existing compression type when used in a `SELECT` query, or the desired compression type when used in an `INSERT` query. Supported compression types are `gz`, `br`, `xz`, `zst`, `lz4`, and `bz2`. **Returned value** A table for reading or writing data in a file. ## Examples for Writing to a File ### Write to a TSV file ```sql INSERT INTO TABLE FUNCTION file('test.tsv', 'TSV', 'column1 UInt32, column2 UInt32, column3 UInt32') VALUES (1, 2, 3), (3, 2, 1), (1, 3, 2) ``` As a result, the data is written into the file `test.tsv`: ```bash # cat /var/lib/clickhouse/user_files/test.tsv 1 2 3 3 2 1 1 3 2 ``` ### Partitioned write to multiple TSV files If you specify a `PARTITION BY` expression when inserting data into a table function of type `file()`, then a separate file is created for each partition. Splitting the data into separate files helps to improve performance of read operations. ```sql INSERT INTO TABLE FUNCTION file('test_{_partition_id}.tsv', 'TSV', 'column1 UInt32, column2 UInt32, column3 UInt32') PARTITION BY column3 VALUES (1, 2, 3), (3, 2, 1), (1, 3, 2) ``` As a result, the data is written into three files: `test_1.tsv`, `test_2.tsv`, and `test_3.tsv`. ```bash # cat /var/lib/clickhouse/user_files/test_1.tsv 3 2 1 # cat /var/lib/clickhouse/user_files/test_2.tsv 1 3 2 # cat /var/lib/clickhouse/user_files/test_3.tsv 1 2 3 ``` ## Examples for Reading from a File ### SELECT from a CSV file First, set `user_files_path` in the server configuration and prepare a file `test.csv`: ``` bash $ grep user_files_path /etc/clickhouse-server/config.xml /var/lib/clickhouse/user_files/ $ cat /var/lib/clickhouse/user_files/test.csv 1,2,3 3,2,1 78,43,45 ``` Then, read data from `test.csv` into a table and select its first two rows: ``` sql SELECT * FROM file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32') LIMIT 2; ``` ``` text ┌─column1─┬─column2─┬─column3─┐ │ 1 │ 2 │ 3 │ │ 3 │ 2 │ 1 │ └─────────┴─────────┴─────────┘ ``` ### Inserting data from a file into a table: ``` sql INSERT INTO FUNCTION file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32') VALUES (1, 2, 3), (3, 2, 1); ``` ```sql SELECT * FROM file('test.csv', 'CSV', 'column1 UInt32, column2 UInt32, column3 UInt32'); ``` ``` text ┌─column1─┬─column2─┬─column3─┐ │ 1 │ 2 │ 3 │ │ 3 │ 2 │ 1 │ └─────────┴─────────┴─────────┘ ``` Reading data from `table.csv`, located in `archive1.zip` or/and `archive2.zip`: ``` sql SELECT * FROM file('user_files/archives/archive{1..2}.zip :: table.csv'); ``` ## 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`. - `**` - Represents all files inside a folder recursively. Constructions with `{}` are similar to the [remote](remote.md) and [hdfs](hdfs.md) table functions. **Example** Suppose there are these files with the following relative paths: - `some_dir/some_file_1` - `some_dir/some_file_2` - `some_dir/some_file_3` - `another_dir/some_file_1` - `another_dir/some_file_2` - `another_dir/some_file_3` Query the total number of rows in all files: ``` sql SELECT count(*) FROM file('{some,another}_dir/some_file_{1..3}', 'TSV', 'name String, value UInt32'); ``` An alternative path expression which achieves the same: ``` sql SELECT count(*) FROM file('{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 total number of rows in files named `file000`, `file001`, … , `file999`: ``` sql SELECT count(*) FROM file('big_dir/file{0..9}{0..9}{0..9}', 'CSV', 'name String, value UInt32'); ``` **Example** Query the total number of rows from all files inside directory `big_dir/` recursively: ``` sql SELECT count(*) FROM file('big_dir/**', 'CSV', 'name String, value UInt32'); ``` **Example** Query the total number of rows from all files `file002` inside any folder in directory `big_dir/` recursively: ``` sql SELECT count(*) FROM file('big_dir/**/file002', 'CSV', 'name String, value UInt32'); ``` ## Virtual Columns {#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 file size is unknown, the value is `NULL`. ## Settings {#settings} - [engine_file_empty_if_not_exists](/docs/en/operations/settings/settings.md#engine-file-empty_if-not-exists) - allows to select empty data from a file that doesn't exist. Disabled by default. - [engine_file_truncate_on_insert](/docs/en/operations/settings/settings.md#engine-file-truncate-on-insert) - allows to truncate file before insert into it. Disabled by default. - [engine_file_allow_create_multiple_files](/docs/en/operations/settings/settings.md#engine_file_allow_create_multiple_files) - allows to create a new file on each insert if format has suffix. Disabled by default. - [engine_file_skip_empty_files](/docs/en/operations/settings/settings.md#engine_file_skip_empty_files) - allows to skip empty files while reading. Disabled by default. - [storage_file_read_method](/docs/en/operations/settings/settings.md#engine-file-empty_if-not-exists) - method of reading data from storage file, one of: read, pread, mmap (only for clickhouse-local). Default value: `pread` for clickhouse-server, `mmap` for clickhouse-local. **See Also** - [Virtual columns](/docs/en/engines/table-engines/index.md#table_engines-virtual_columns) - [Rename files after processing](/docs/en/operations/settings/settings.md#rename_files_after_processing)