15 posts tagged with "Performance and Optimizations"

Covers a common reason why a primary key is not used in ordering and how we can confirm

Learn how to profile ClickHouse using LLVM's XRay instrumentation profiler, visualize traces, and analyze performance.

Tips and tricks on optimizing basic data types in ClickHouse

Learn how to ensure data consistency when reading from ClickHouse, whether you're connected to the same node or a random node.

Learn how to check if query cache is being utilized in ClickHouse using `clickhouse-client` trace logs or SQL commands.

Learn how to use the `FORMAT Null` option in ClickHouse to measure query processing time without returning any rows to the client.

Learn how to use the `system.query_log` table to find the most memory-intensive queries in ClickHouse, with examples for clustered and standalone setups.

Learn how to calculate the ratio of empty or zero values in every column of a ClickHouse table to optimize sparse column serialization.

Learn how to use the `query_log` table in ClickHouse to identify the most memory and CPU-intensive queries across distributed nodes.

The new setting `allow_asynchronous_read_from_io_pool_for_merge_tree` allows the number of reading threads (streams) to be higher than the number of threads in the rest of the query execution pipeline.