v.20.10New Feature
New settings for query complexity limits in distributed queries
New query complexity limit settingsmax_rows_to_read_leaf,max_bytes_to_read_leaffor distributed queries to limit max rows/bytes read on the leaf nodes. Limit is applied for local reads only, excluding the final merge stage on the root node. #14221 (Roman Khavronenko).
Why it matters
These settings help control resource usage and prevent excessive data reading on individual leaf nodes during distributed query execution. By applying limits locally on each shard before the final merge on the root node, users can manage load and improve query stability and performance.How to use it
Configure themax_rows_to_read_leaf and max_bytes_to_read_leaf settings in the query or server configuration to set maximum rows and bytes read per leaf node. These limits affect only local reads on the leaf nodes and exclude the root node's merging stage.