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pych-client

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pych-client is a ClickHouse client for Python built on top of httpx. It targets the HTTP interface and offers the following features:

  • Sync (ClickHouseClient) and async (AsyncClickHouseClient) clients.
  • Streaming requests and responses.
  • Load credentials from environment variables, or from a configuration file.

Installation

# Default Python JSON parser:
pip install pych-client
# Faster orjson parser:
pip install pych-client[orjson]

Usage

from pych_client import AsyncClickHouseClient, ClickHouseClient

# See "Credential provider chain" for more information on credential specification.
credentials = dict(
    base_url="http://localhost:8123",
    database="default",
    username="default",
    password=""
)

# The client can be used directly, or as a context manager.
# The context manager will ensure that the HTTP client resources
# are properly cleaned-up on exit.
with ClickHouseClient(**credentials) as client:
    # `.bytes()` and `.text()` return the raw response content from the database.
    # `.json()` sets the format to `JSONEachRow` and parse the response content.
    client.bytes("SELECT arrayJoin([1, 2, 3]) AS a")
    # b'1\n2\n3\n'
    client.text("SELECT arrayJoin([1, 2, 3]) AS a")
    # '1\n2\n3\n'
    client.json("SELECT arrayJoin([1, 2, 3]) AS a")
    # [{'a': 1}, {'a': 2}, {'a': 3}]

    # `.iter_bytes()`, `.iter_text()` and `.iter_json()` return the response content
    # as it is received from the database, without buffering the entire response.
    # `.iter_text()` iterates on the line of the response.
    list(client.iter_bytes("SELECT arrayJoin([1, 2, 3]) AS a"))
    # [b'1\n2\n3\n', b'']
    list(client.iter_text("SELECT arrayJoin([1, 2, 3]) AS a"))
    # ['1', '2', '3']
    list(client.iter_json("SELECT arrayJoin([1, 2, 3]) AS a"))
    # [{'a': 1}, {'a': 2}, {'a': 3}]

    # In addition to the query, the following arguments can be set:
    # - `params`: a mapping of query parameters to their values.
    # - `data`: a bytes, string or an interator of bytes to send in the request body.
    # - `settings`: ClickHouse settings (e.g. `{"default_format": "JSONEachRow"`).
    params = {"table": "test_pych"}
    client.text('''
        CREATE TABLE {table:Identifier} (a Int64, b Int64)
        ENGINE MergeTree() ORDER BY (a, b)
    ''', params)
    client.text("INSERT INTO {table:Identifier} VALUES", params, "(1, 2)")
    client.text("INSERT INTO {table:Identifier} VALUES", params, [b"(3, 4)", b"(5, 6)"])
    client.json("SELECT * FROM {table:Identifier} ORDER BY a", params)
    # [{'a': '1', 'b': '2'}, {'a': '3', 'b': '4'}, {'a': '5', 'b': '6'}]

# `AsyncClickHouseClient` offers the same methods:
async with AsyncClickHouseClient(**credentials) as client:
    # Example usage for `.json()` and `.iter_json()`:
    await client.json("SELECT arrayJoin([1, 2, 3]) AS a")
    # [{'a': 1}, {'a': 2}, {'a': 3}]
    async for row in client.iter_json("SELECT arrayJoin([1, 2, 3]) AS a"):
        ...

Command-line interface

pych-client --help

Credential provider chain

The client looks for credentials in a way similar to the AWS SDK:

  1. If one of base_url, database, username or password is specified, these values will be used.
  2. If none of the previous values are specified, and one of PYCH_BASE_URL, PYCH_DATABASE, PYCH_USERNAME or PYCH_PASSWORD environment variables are present, these values will be used.
  3. If none of the previous values are specified, and the file ~/.config/pych-client/credentials.json exists, the fields base_url, database and username and password will be used.
  4. If none of the previous values are specified, the values http://localhost:8213, default and default will be used.