v.18.12Improvement

Improved GROUP BY Performance with Mixed Aggregation Fields

Official CH changelog text
Improved performance of GROUP BY with multiple aggregation fields when one of them is string and the others are fixed length.
Improves the performance of GROUP BY queries that include multiple aggregation fields where at least one field is a string and the others are fixed-length types.

Why it matters

This feature addresses the inefficiency in processing GROUP BY operations involving mixed data types (string and fixed-length). It optimizes query execution to reduce latency and resource consumption, enhancing overall query performance for such aggregation patterns.

How to use it

No specific user action is required to enable this improvement. The optimization is applied automatically by ClickHouse when executing GROUP BY queries containing multiple aggregation fields with the described data types.
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