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46 lines
1.3 KiB
Markdown
46 lines
1.3 KiB
Markdown
# HDFS {#table_engines-hdfs}
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This engine provides integration with [Apache Hadoop](https://en.wikipedia.org/wiki/Apache_Hadoop) ecosystem by allowing to manage data on [HDFS](https://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-hdfs/HdfsDesign.htmll)via ClickHouse. This engine is similar
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to the [File](file.md) and [URL](url.md) engines, but provides Hadoop-specific features.
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## Usage
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```
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ENGINE = HDFS(URI, format)
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```
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The `format` parameter specifies one of the available file formats. To perform
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`SELECT` queries, the format must be supported for input, and to perform
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`INSERT` queries -- for output. The available formats are listed in the
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[Formats](../../interfaces/formats.md#formats) section.
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**Example:**
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**1.** Set up the `HDFS_engine_table` table:
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``` sql
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CREATE TABLE hdfs_engine_table (name String, value UInt32) ENGINE=HDFS('hdfs://hdfs1:9000/other_storage', 'TSV')
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```
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**2.** Query the data:
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``` sql
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SELECT * FROM hdfs_engine_table LIMIT 2
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```
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```
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┌─name─┬─value─┐
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│ one │ 1 │
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│ two │ 2 │
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└──────┴───────┘
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```
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## Details of Implementation
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- Reads and writes can be parallel
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- Not supported:
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- `ALTER` and `SELECT...SAMPLE` operations.
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- Indexes.
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- Replication.
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[Original article](https://clickhouse.yandex/docs/en/operations/table_engines/hdfs/) <!--hide-->
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