clickhouse-driver 0.0.4

Python driver with native interface for ClickHouse

ClickHouse Python Driver

ClickHouse Python Driver with native (TCP) interface support.

Features

• Compression support:

  • QuickLZ (isn’t fully tested)

  • LZ4/LZ4HC

  • ZSTD

• Basic types support:

  • Float32/64

  • [U]Int8/16/32/64

  • Date/DateTime

  • String/FixedString(N)

  • Enum8/16

  • Array(T)

• External data for query processing.

Installation

The package can be installed using pip:

pip install clickhouse-driver

You can install extras packages if you need compression support. Example of LZ4 compression requirements installation:

pip install clickhouse-driver[lz4]

You also can specify multiple extras by using comma. Install LZ4 and ZSTD requirements:

pip install clickhouse-driver[lz4,zstd]

Usage example:

from clickhouse_driver.client import Client

client = Client('localhost')

print(client.execute('SHOW TABLES'))

client.execute('DROP TABLE IF EXISTS test')

client.execute('CREATE TABLE test (x Int32) ENGINE = Memory')

client.execute(
    'INSERT INTO test (x) VALUES',
    [{'x': 1}, {'x': 2}, {'x': 3}, {'x': 100}]
)
client.execute('INSERT INTO test (x) VALUES', [[200]])

print(client.execute('SELECT sum(x) FROM test'))

Arrays:

client.execute('CREATE TABLE test2 (x Array(Int32)) ENGINE = Memory')
client.execute(
    'INSERT INTO test2 (x) VALUES',
    [{'x': [10, 20, 30]}, {'x': (11, 21, 31)}]
)

print(client.execute('SELECT * FROM test2'))

Enums:

from enum import Enum

class MyEnum(Enum):
    foo = 1
    bar = 2

client.execute('''
    CREATE TABLE test3
    (
        x Enum8('foo' = 1, 'bar' = 2)
    ) ENGINE = Memory
''')
client.execute(
    'INSERT INTO test3 (x) VALUES',
    [{'x': MyEnum.foo}, {'x': 'bar'}, {'x': 1}]
)

print(client.execute('SELECT * FROM test3'))

Data compression:

from clickhouse_driver.client import Client

client_with_lz4 = Client('localhost', compression=True)
client_with_lz4 = Client('localhost', compression='lz4')
client_with_zstd = Client('localhost', compression='zstd')

External data for query processing:

tables = [{
    'name': 'ext',
    'structure': [('x', 'Int32'), ('y', 'Array(Int32)')],
    'data': [
        {'x': 100, 'y': [2, 4, 6, 8]},
        {'x': 500, 'y': [1, 3, 5, 7]},
    ]
}]
rv = self.client.execute(
    'SELECT sum(x) FROM ext', external_tables=tables)
print(rv)

CityHash algorithm notes

Unfortunately ClickHouse server comes with built-in old version of CityHash hashing algorithm. That’s why we can’t use original CityHash package. Downgraded version of this algorithm is placed at PyPi.

Connection Parameters

The first parameter host is required. There are some optional parameters:

• port is port ClickHouse server is bound to. Default is 9000.

• database is database connect to. Default is 'default'.

• user. Default is 'default'.

• password. Default is '' (no password).

• client_name. This name will appear in server logs. Default is 'pyclient'.

• compression. Whether or not use compression. Default is False.Possible choices:

  • True is equivalent to 'lz4'.

  • 'quicklz'.

  • 'lz4'.

  • 'lz4hc' high-compression variant of 'lz4'.

  • 'zstd'.

You can also specify timeouts via:

• connect_timeout. Default is 10 seconds.

• send_receive_timeout. Default is 300 seconds.

• sync_request_timeout. Default is 5 seconds.

License

ClickHouse Python Driver is distributed under the MIT license.