cshuo opened a new issue, #20441:
URL: https://github.com/apache/hudi/issues/20441

   Follow-up to https://github.com/apache/hudi/pull/20328 and 
https://github.com/apache/hudi/issues/20296.
   
   Before this fix, expanding `hoodie.metadata.index.column.stats.column.list` 
and subsequently writing new files into an existing partition could produce 
partition statistics covering only the files with statistics for the newly 
indexed column.
   
   These aggregates can have non-null counts and min/max values, making them 
indistinguishable from complete statistics to the read-time missing-statistics 
guard. For example, an older file may contain `name = 'alice'`, while the 
stored partition bounds cover only a newer file containing `name = 'bob'`. A 
query for `name = 'alice'` can then incorrectly prune the entire partition.
   
   The PR checks file coverage when generating partition statistics and 
invalidates incomplete aggregates. It does not detect or repair historical 
aggregates in partitions that are not subsequently processed. Upgrading alone 
therefore does not repair all affected tables.
   
   This follow-up should address detection and repair of historical incomplete 
partition statistics, including partitions untouched after upgrade, and 
document a supported rebuild procedure. Regression coverage should start with 
partial aggregates created before the fix and verify correct query results 
after repair, including cases where some file-level column statistics remain 
missing.
   
   Tables that expanded the indexed column list before the fix should rebuild 
the partition stats index using a version containing the fix.
   


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