База знаний

Learn how to configure the Global Thread pool in ClickHouse by adjusting settings like `max_thread_pool_size`, `thread_pool_queue_size`, and `max_thread_pool_free_size`.

Learn how to use the `skip_check_for_incorrect_settings` option to allow ClickHouse to start even when user-level settings are specified incorrectly.

Learn how to capture server logs at the client level, even with different log settings, using the `send_logs_level` client setting.

A query to compare metrics between two queries in ClickHouse.

Learn how to resolve ingest failures caused by stricter grant checking introduced in ClickHouse 23.9 for tables using `async_inserts`. Update grants to fix errors.

Learn how to optimize Map column lookups in ClickHouse for better query performance by materializing specific keys as standalone columns.

The short answer is "yes". ClickHouse has multiple mechanisms that allow freeing up disk space by removing old data. Each mechanism is aimed for different scenarios.

Learn how to check if a projection is used in ClickHouse queries by testing with sample data and using EXPLAIN to verify projection usage.

An example using Python and requests module to write and read to ClickHouse

How to enforce limit on max query execution time