v.24.5Backward Incompatible Changes
Improved Query Performance and Access Control in system.columns
Queries fromsystem.columnswill work faster if there is a large number of columns, but many databases or tables are not granted forSHOW TABLES. Note that in previous versions, if you grantSHOW COLUMNSto individual columns without grantingSHOW TABLESto the corresponding tables, thesystem.columnstable will show these columns, but in a new version, it will skip the table entirely. Remove trace log messages "Access granted" and "Access denied" that slowed down queries. #63439 (Alexey Milovidov).