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105 lines
3.4 KiB
Markdown
105 lines
3.4 KiB
Markdown
---
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machine_translated: true
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machine_translated_rev: 72537a2d527c63c07aa5d2361a8829f3895cf2bd
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toc_priority: 45
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toc_title: hdfs
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---
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# hdfs {#hdfs}
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HDFS内のファイルからテーブルを作成します。 この表関数は次のようになります [url](url.md) と [ファイル](file.md) ワンズ
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``` sql
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hdfs(URI, format, structure)
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```
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**入力パラメータ**
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- `URI` — The relative URI to the file in HDFS. Path to file support following globs in readonly mode: `*`, `?`, `{abc,def}` と `{N..M}` どこに `N`, `M` — numbers, \``'abc', 'def'` — strings.
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- `format` — The [形式](../../interfaces/formats.md#formats) ファイルの。
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- `structure` — Structure of the table. Format `'column1_name column1_type, column2_name column2_type, ...'`.
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**戻り値**
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テーブルの指定された構造を読み取りまたは書き込みデータを、指定されたファイルです。
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**例**
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テーブルから `hdfs://hdfs1:9000/test` そして、それから最初の二つの行の選択:
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``` sql
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SELECT *
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FROM hdfs('hdfs://hdfs1:9000/test', 'TSV', 'column1 UInt32, column2 UInt32, column3 UInt32')
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LIMIT 2
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```
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``` text
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┌─column1─┬─column2─┬─column3─┐
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│ 1 │ 2 │ 3 │
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│ 3 │ 2 │ 1 │
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└─────────┴─────────┴─────────┘
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```
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**パス内のグロブ**
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複数のパスコンポーネ のための処理中のファイルが存在するマッチのパスのパターンのみならず接尾辞または接頭).
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- `*` — Substitutes any number of any characters except `/` 空の文字列を含む。
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- `?` — Substitutes any single character.
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- `{some_string,another_string,yet_another_one}` — Substitutes any of strings `'some_string', 'another_string', 'yet_another_one'`.
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- `{N..M}` — Substitutes any number in range from N to M including both borders.
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構造との `{}` に類似しています [遠隔テーブル機能](../../sql-reference/table-functions/remote.md)).
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**例**
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1. HDFSに次のUriを持つ複数のファイルがあるとします:
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- ‘hdfs://hdfs1:9000/some\_dir/some\_file\_1’
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- ‘hdfs://hdfs1:9000/some\_dir/some\_file\_2’
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- ‘hdfs://hdfs1:9000/some\_dir/some\_file\_3’
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- ‘hdfs://hdfs1:9000/another\_dir/some\_file\_1’
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- ‘hdfs://hdfs1:9000/another\_dir/some\_file\_2’
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- ‘hdfs://hdfs1:9000/another\_dir/some\_file\_3’
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1. これらのファイル内の行の量を照会します:
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<!-- -->
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``` sql
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SELECT count(*)
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FROM hdfs('hdfs://hdfs1:9000/{some,another}_dir/some_file_{1..3}', 'TSV', 'name String, value UInt32')
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```
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1. クエリの量の行のすべてのファイルのディレクトリ:
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<!-- -->
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``` sql
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SELECT count(*)
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FROM hdfs('hdfs://hdfs1:9000/{some,another}_dir/*', 'TSV', 'name String, value UInt32')
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```
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!!! warning "警告"
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ファイ `?`.
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**例**
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クエリからのデータファイル名 `file000`, `file001`, … , `file999`:
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``` sql
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SELECT count(*)
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FROM hdfs('hdfs://hdfs1:9000/big_dir/file{0..9}{0..9}{0..9}', 'CSV', 'name String, value UInt32')
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```
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## 仮想列 {#virtual-columns}
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- `_path` — Path to the file.
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- `_file` — Name of the file.
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**も参照。**
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- [仮想列](https://clickhouse.tech/docs/en/operations/table_engines/#table_engines-virtual_columns)
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[元の記事](https://clickhouse.tech/docs/en/query_language/table_functions/hdfs/) <!--hide-->
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