ClickHouse is a popular open-source columnar database management system known for its high performance and efficient query execution. To maintain optimal performance and manage storage resources effectively, ClickHouse provides the OPTIMIZE and OPTIMIZE FINAL commands. […]
The query filters the data from the ‘system.query_log’ table to include only entries of type 2 (QueryFinish) and 4 (ExceptionWhileProcessing) and groups the results by the ‘normalized_query_hash’. The results are then sorted by the difference […]
Following query will show you ClickHouse Disks via reading system.disks table. SELECT name, path, formatReadableSize(sum(free_space)) as free_space, formatReadableSize(sum(total_space)) as total_space, formatReadableSize(sum(keep_free_space)) as keep_free_space, type FROM system.disks GROUP BY name, path, type FORMAT PrettyCompact Example Output: […]
Following sql query will show you queries that being processed. SELECT user, address as client, elapsed as time_seconds, formatReadableSize(memory_usage) as memory, formatReadableSize(read_bytes) as read, read_rows, total_rows_approx as total_rows, query_id, substring(query,1,40) as query FROM system.processes ORDER […]
We developed a shard config xml generator for ClickHouse. All you have to do download and run the python script and enter your cluster informations to generate an example config file. Download file via GitHub […]
Introduction In ClickHouse, which is an open-source columnar database management system, the parameters you’ve mentioned are related to the configuration of distributed tables and how data is handled within a distributed environment. A distributed table […]
Introduction In the world of data analytics and storage, databases are the backbone that supports businesses’ decision-making processes. ClickHouse, an open-source columnar database management system, has gained popularity for its exceptional speed and efficiency in […]
Introduction In the world of modern software development, managing data efficiently and effectively is crucial for maintaining a successful and scalable application. One of the techniques that has gained popularity in recent years is […]
Introduction Database as a Service (DBaaS) is a managed service offered by the cloud that allows access to databases without the demand for physical hardware setup, software installation, or database setup. The ChistaDATA Cloud (DBaaS) […]
The new feature of empty part removal was introduced in version 20.12. If TTL removes all rows from a part, older versions leave empty parts (with 0 rows) (see https://github.com/ClickHouse/ClickHouse/issues/5491). If you establish a TTL […]
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