Project: ClickHouse (App Definition and Development / Database)
File: file.md

slug: /en/sql-reference/table-functions/file sidebar_position: 60 sidebar_label: file A table engine which provides a table-like interface to SELECT from and INSERT into files, similar to the 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([pathtoarchive ::] path [,format] [,structure] [,compression]) ``` Parameters `path` The relative path to the file from . Supports in read-only mode the following : `*`, `?`, `{abc,def}` (with `'abc'` and `'def'` being strings) and `{N..M}` (with `N` and `M` being numbers). `pathtoarchive` - The relative path to a zip/tar/7z archive. Supports the same globs as `path`. `format` The of the file. `structure` Structure of the table. Format: `'column1name column1type, column2name column2type, ...'`. `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. ```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 1 2 3 3 2 1 1 3 2 ``` 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: `test1.tsv`, `test2.tsv`, and `test_3.tsv`. ```bash 3 2 1 1 3 2 1 2 3 ``` First, set `userfilespath` in the server configuration and prepare a file `test.csv`: ``` bash $ grep userfilespath /etc/clickhouse-server/config.xml <userfilespath>/var/lib/clickhouse/userfiles/</userfiles_path> $ 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 column1column2column3 1 2 3 3 2 1 ``` ``` sql INSERT INTO FUNCTION

'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 column1column2column3 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'); ``` 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. `{somestring,anotherstring,yetanotherone}` Substitutes any of strings `'somestring', 'anotherstring', 'yetanotherone'`. 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 and table functions. Example Suppose there are these files with the following relative paths: `somedir/somefile_1` `somedir/somefile_2` `somedir/somefile_3` `anotherdir/somefile_1` `anotherdir/somefile_2` `anotherdir/somefile_3` Query the total number of rows in all files: ``` sql SELECT count(*) FROM file('{some,another}dir/somefile_{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'); ``` `_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`. - allows to select empty data from a file that doesn't exist. Disabled by default. - allows to truncate file before insert into it. Disabled by default. - allows to create a new file on each insert if format has suffix. Disabled by default. - allows to skip empty files while reading. Disabled by default. - 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