mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-11 08:52:06 +00:00
84 lines
3.4 KiB
Markdown
84 lines
3.4 KiB
Markdown
---
|
|
slug: /en/sql-reference/table-functions/fileCluster
|
|
sidebar_position: 61
|
|
sidebar_label: fileCluster
|
|
---
|
|
|
|
# fileCluster Table Function
|
|
|
|
Enables simultaneous processing of files matching a specified path across multiple nodes within a cluster. The initiator establishes connections to worker nodes, expands globs in the file path, and delegates file-reading tasks to worker nodes. Each worker node is querying the initiator for the next file to process, repeating until all tasks are completed (all files are read).
|
|
|
|
:::note
|
|
This function will operate _correctly_ only in case the set of files matching the initially specified path is identical across all nodes, and their content is consistent among different nodes.
|
|
In case these files differ between nodes, the return value cannot be predetermined and depends on the order in which worker nodes request tasks from the initiator.
|
|
:::
|
|
|
|
**Syntax**
|
|
|
|
``` sql
|
|
fileCluster(cluster_name, path[, format, structure, compression_method])
|
|
```
|
|
|
|
**Arguments**
|
|
|
|
- `cluster_name` — Name of a cluster that is used to build a set of addresses and connection parameters to remote and local servers.
|
|
- `path` — The relative path to the file from [user_files_path](/docs/en/operations/server-configuration-parameters/settings.md#user_files_path). Path to file also supports [globs](#globs-in-path).
|
|
- `format` — [Format](../../interfaces/formats.md#formats) of the files. Type: [String](../../sql-reference/data-types/string.md).
|
|
- `structure` — Table structure in `'UserID UInt64, Name String'` format. Determines column names and types. Type: [String](../../sql-reference/data-types/string.md).
|
|
- `compression_method` — Compression method. Supported compression types are `gz`, `br`, `xz`, `zst`, `lz4`, and `bz2`.
|
|
|
|
**Returned value**
|
|
|
|
A table with the specified format and structure and with data from files matching the specified path.
|
|
|
|
**Example**
|
|
|
|
Given a cluster named `my_cluster` and given the following value of setting `user_files_path`:
|
|
|
|
``` bash
|
|
$ grep user_files_path /etc/clickhouse-server/config.xml
|
|
<user_files_path>/var/lib/clickhouse/user_files/</user_files_path>
|
|
```
|
|
Also, given there are files `test1.csv` and `test2.csv` inside `user_files_path` of each cluster node, and their content is identical across different nodes:
|
|
```bash
|
|
$ cat /var/lib/clickhouse/user_files/test1.csv
|
|
1,"file1"
|
|
11,"file11"
|
|
|
|
$ cat /var/lib/clickhouse/user_files/test2.csv
|
|
2,"file2"
|
|
22,"file22"
|
|
```
|
|
|
|
For example, one can create these files by executing these two queries on every cluster node:
|
|
```sql
|
|
INSERT INTO TABLE FUNCTION file('file1.csv', 'CSV', 'i UInt32, s String') VALUES (1,'file1'), (11,'file11');
|
|
INSERT INTO TABLE FUNCTION file('file2.csv', 'CSV', 'i UInt32, s String') VALUES (2,'file2'), (22,'file22');
|
|
```
|
|
|
|
Now, read data contents of `test1.csv` and `test2.csv` via `fileCluster` table function:
|
|
|
|
```sql
|
|
SELECT * FROM fileCluster('my_cluster', 'file{1,2}.csv', 'CSV', 'i UInt32, s String') ORDER BY i, s
|
|
```
|
|
|
|
```
|
|
┌──i─┬─s──────┐
|
|
│ 1 │ file1 │
|
|
│ 11 │ file11 │
|
|
└────┴────────┘
|
|
┌──i─┬─s──────┐
|
|
│ 2 │ file2 │
|
|
│ 22 │ file22 │
|
|
└────┴────────┘
|
|
```
|
|
|
|
|
|
## Globs in Path
|
|
|
|
All patterns supported by [File](../../sql-reference/table-functions/file.md#globs-in-path) table function are supported by FileCluster.
|
|
|
|
**See Also**
|
|
|
|
- [File table function](../../sql-reference/table-functions/file.md)
|