I created a table copied from another table, but sorted, partially using Impala and partially using Hive. I invalidated the table metadata. When I run COMPUTE STATS on the table the SELECT COUNT query runs for awhile and then stops making progress. After that point, comparing snapshots of the profile reveals that only one SCAN fragment seems to be active, but its RowsRead counter is moving backwards, and even goes negative. When I kill the query and try again, the problem reproduces, hanging at the same point in the scan progress.