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80 lines
2.0 KiB
Markdown
80 lines
2.0 KiB
Markdown
<a name="table_engines-url"></a>
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# URL(URL, Format)
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Manages data on a remote HTTP/HTTPS server. This engine is similar
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to the [`File`](./file.md#) engine.
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## Using the engine in the ClickHouse server
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`The format` must be one that ClickHouse can use in
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`SELECT` queries and, if necessary, in `INSERTs`. For the full list of supported formats, see
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[Formats](../../interfaces/formats.md#formats).
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`The URL` must conform to the structure of a Uniform Resource Locator. The specified URL must point to a server
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that uses HTTP or HTTPS. This does not require any
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additional headers for getting a response from the server.
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`INSERT` and `SELECT` queries are transformed to `POST` and `GET` requests,
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respectively. For processing `POST` requests, the remote server must support
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[Chunked transfer encoding](https://en.wikipedia.org/wiki/Chunked_transfer_encoding).
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**Example:**
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**1.** Create a `url_engine_table` table on the server :
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```sql
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CREATE TABLE url_engine_table (word String, value UInt64)
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ENGINE=URL('http://127.0.0.1:12345/', CSV)
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```
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**2.** Create a basic HTTP server using the standard Python 3 tools and
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start it:
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```python3
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from http.server import BaseHTTPRequestHandler, HTTPServer
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class CSVHTTPServer(BaseHTTPRequestHandler):
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def do_GET(self):
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self.send_response(200)
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self.send_header('Content-type', 'text/csv')
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self.end_headers()
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self.wfile.write(bytes('Hello,1\nWorld,2\n', "utf-8"))
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if __name__ == "__main__":
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server_address = ('127.0.0.1', 12345)
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HTTPServer(server_address, CSVHTTPServer).serve_forever()
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```
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```bash
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python3 server.py
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```
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**3.** Request data:
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```sql
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SELECT * FROM url_engine_table
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```
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```text
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┌─word──┬─value─┐
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│ Hello │ 1 │
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│ World │ 2 │
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└───────┴───────┘
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```
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## Usage
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<<<<<<< HEAD
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- Multi-stream reading and writing are supported.
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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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>>>>>>> upstream/master
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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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