v.22.5Improvement
Fix Exception for Obsolete Setting in ClickHouse Configuration
After #36425 settings likebackground_fetches_pool_sizebecame obsolete and can appear in top level config, but clickhouse throws and exception likeError updating configuration from '/etc/clickhouse-server/config.xml' config.: Code: 137. DB::Exception: A setting 'background_fetches_pool_size' appeared at top level in config /etc/clickhouse-server/config.xml.This is fixed. #36917 (Nikita Mikhaylov).
Why it matters
Previously, after the changes introduced in issue #36425, certain settings became obsolete and could appear at the top level in the config file. However, ClickHouse would throw an error and refuse to start if these settings were present at the top level, causing confusion and operational issues. This fix prevents such exceptions, allowing legacy or obsolete top-level settings to be ignored or handled gracefully, improving configuration stability and user experience.How to use it
Users can keep or remove obsolete settings likebackground_fetches_pool_size at the top level of their config.xml without causing startup errors. No additional configuration is required; the fix is applied automatically when upgrading to the fixed ClickHouse version.