v.25.10Improvement
Fix optimization pass
Fixed optimization pass for redundant equal expression when LowCardinality of the resulting type differs before and after optimization. #82651 (Yakov Olkhovskiy).Why it matters
This fix addresses an issue in the optimization pass where redundant equal expressions usingLowCardinality columns could result in incorrect types after optimization. It ensures consistent handling of type changes, improving query correctness and stability when working with LowCardinality data.How to use it
This fix is applied internally in ClickHouse's query optimizer. Users do not need to enable anything explicitly; it automatically improves the handling of redundant equal expressions withLowCardinality columns after upgrading to the version including this fix.