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url Table Function

url function creates a table from the URL with given format and structure.

url function may be used in SELECT and INSERT queries on data in URL tables.

Syntax​

url(URL [,format] [,structure] [,headers])

Parameters​

ParameterDescription
URLSingle quoted HTTP or HTTPS server address, which can accept GET or POST requests (for SELECT or INSERT queries correspondingly). Type: String.
formatFormat of the data. Type: String.
structureTable structure in 'UserID UInt64, Name String' format. Determines column names and types. Type: String.
headersHeaders in 'headers('key1'='value1', 'key2'='value2')' format. You can set headers for HTTP call.

Returned value​

A table with the specified format and structure and with data from the defined URL.

Examples​

Getting the first 3 lines of a table that contains columns of String and UInt32 type from HTTP-server which answers in CSV format.

SELECT * FROM url('http://127.0.0.1:12345/', CSV, 'column1 String, column2 UInt32', headers('Accept'='text/csv; charset=utf-8')) LIMIT 3;

Inserting data from a URL into a table:

CREATE TABLE test_table (column1 String, column2 UInt32) ENGINE=Memory;
INSERT INTO FUNCTION url('http://127.0.0.1:8123/?query=INSERT+INTO+test_table+FORMAT+CSV', 'CSV', 'column1 String, column2 UInt32') VALUES ('http interface', 42);
SELECT * FROM test_table;

Globs in URL​

Patterns in curly brackets { } are used to generate a set of shards or to specify failover addresses. Supported pattern types and examples see in the description of the remote function. Character | inside patterns is used to specify failover addresses. They are iterated in the same order as listed in the pattern. The number of generated addresses is limited by glob_expansion_max_elements setting.

Virtual Columns​

  • _path — Path to the URL. Type: LowCardinality(String).
  • _file — Resource name of the URL. Type: LowCardinality(String).
  • _size — Size of the resource in bytes. Type: Nullable(UInt64). If the size is unknown, the value is NULL.
  • _time — Last modified time of the file. Type: Nullable(DateTime). If the time is unknown, the value is NULL.
  • _headers - HTTP response headers. Type: Map(LowCardinality(String), LowCardinality(String)).

use_hive_partitioning setting​

When setting use_hive_partitioning is set to 1, ClickHouse will detect Hive-style partitioning in the path (/name=value/) and will allow to use partition columns as virtual columns in the query. These virtual columns will have the same names as in the partitioned path, but starting with _.

Example

Use virtual column, created with Hive-style partitioning

SELECT * FROM url('http://data/path/date=*/country=*/code=*/*.parquet') WHERE _date > '2020-01-01' AND _country = 'Netherlands' AND _code = 42;

Storage Settings​

Permissions​

url function requires CREATE TEMPORARY TABLE permission. As such - it'll not work for users with readonly = 1 setting. At least readonly = 2 is required.