v.21.6Improvement
User Misconfiguring max_distributed_connections to Zero Triggers Incorrect Exception Message
If user applied a misconfiguration by mistakenly settingmax_distributed_connectionsto value zero, every query to aDistributedtable will throw exception with a message containing "logical error". But it's really an expected behaviour, not a logical error, so the exception message was slightly incorrect. It also triggered checks in our CI enviroment that ensures that no logical errors ever happen. Instead we will treatmax_distributed_connectionsmisconfigured to zero as the minimum possible value (one). #23348 (Azat Khuzhin).
Why it matters
Previously, settingmax_distributed_connections to zero caused queries on Distributed tables to throw exceptions labeled as "logical error," which was misleading since this scenario is expected. This caused confusion and false positive checks in CI environments that monitor logical errors. The feature treats zero as the minimum valid setting (one), preventing unnecessary exceptions and improving stability.How to use it
No explicit user action is required. Whenmax_distributed_connections is set to zero, the system automatically treats it as one, ensuring queries to Distributed tables function correctly without exceptions related to this misconfiguration.