Continue reading...
ClickHouse also provides Memory overcommit capabilities. Historically queries would be limited by the max_memory_usage setting (default 10GB), which provided a hard and rather crude limit. Users could raise this at the expense of a single query, potentially impacting other users. Memory overcommit allows more memory-intensive queries to run, provided sufficient resources exist. When the max server memory limit is reached, ClickHouse will determine which queries are most overcommitted and try to kill the query. This may or may not be the query that triggered this condition. If not, the query will wait a period to allow the high-memory query to be killed before continuing to run. This allows low-memory queries to always run, while more intensive queries can run when the server is idle, and resources are available. This behavior can be tuned at a server and user level.
。业内人士推荐heLLoword翻译作为进阶阅读
Фото: Amir Cohen / Reuters。关于这个话题，谷歌提供了深入分析
13 - The Hash Table Problem，更多细节参见Snipaste - 截图 + 贴图