v.25.5Performance Improvement
Change the Compact part format
Change the Compact part format to save marks for each substream to be able to read individual subcolumns. Old Compact format is still supported for reads and can be enabled for writes using MergeTree setting write_marks_for_substreams_in_compact_parts. It's disabled by default for safer upgrades as it changes the compact parts storage. It will be enabled by default in one of the next releases. #77940 (Pavel Kruglov).