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3.5 KiB
Markdown
84 lines
3.5 KiB
Markdown
---
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slug: /en/sql-reference/table-functions/fileCluster
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sidebar_position: 61
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sidebar_label: fileCluster
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---
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# fileCluster Table Function
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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).
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:::note
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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.
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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.
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:::
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**Syntax**
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``` sql
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fileCluster(cluster_name, path[, format, structure, compression_method])
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```
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**Arguments**
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- `cluster_name` — Name of a cluster that is used to build a set of addresses and connection parameters to remote and local servers.
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- `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). Path to file also supports [globs](#globs_in_path).
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- `format` — [Format](../../interfaces/formats.md#formats) of the files. Type: [String](../../sql-reference/data-types/string.md).
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- `structure` — Table structure in `'UserID UInt64, Name String'` format. Determines column names and types. Type: [String](../../sql-reference/data-types/string.md).
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- `compression_method` — Compression method. Supported compression types are `gz`, `br`, `xz`, `zst`, `lz4`, and `bz2`.
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**Returned value**
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A table with the specified format and structure and with data from files matching the specified path.
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**Example**
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Given a cluster named `my_cluster` and given the following value of setting `user_files_path`:
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``` bash
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$ grep user_files_path /etc/clickhouse-server/config.xml
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<user_files_path>/var/lib/clickhouse/user_files/</user_files_path>
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```
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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:
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```bash
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$ cat /var/lib/clickhouse/user_files/test1.csv
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1,"file1"
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11,"file11"
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$ cat /var/lib/clickhouse/user_files/test2.csv
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2,"file2"
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22,"file22"
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```
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For example, one can create these files by executing these two queries on every cluster node:
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```sql
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INSERT INTO TABLE FUNCTION file('file1.csv', 'CSV', 'i UInt32, s String') VALUES (1,'file1'), (11,'file11');
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INSERT INTO TABLE FUNCTION file('file2.csv', 'CSV', 'i UInt32, s String') VALUES (2,'file2'), (22,'file22');
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```
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Now, read data contents of `test1.csv` and `test2.csv` via `fileCluster` table function:
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```sql
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SELECT * FROM fileCluster('my_cluster', 'file{1,2}.csv', 'CSV', 'i UInt32, s String') ORDER BY i, s
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```
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```
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┌──i─┬─s──────┐
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│ 1 │ file1 │
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│ 11 │ file11 │
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└────┴────────┘
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┌──i─┬─s──────┐
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│ 2 │ file2 │
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│ 22 │ file22 │
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└────┴────────┘
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```
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## Globs in Path {#globs_in_path}
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All patterns supported by [File](../../sql-reference/table-functions/file.md#globs-in-path) table function are supported by FileCluster.
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**See Also**
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- [File table function](../../sql-reference/table-functions/file.md)
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