Alter column fails due to “hidden” statistic

Question

I'm trying to change a column data type from datetime2 to datetimeoffset. I have db owner permissions.

Whenever I run the query:

alter table dbo.<my-table>
alter column [TimeStamp] datetimeoffset

I get the following error message:

The statistics 'Stat_a41cbd7f968a4cba86199c960f6f7c3a' is dependent on column 'TimeStamp'.

ALTER TABLE ALTER COLUMN TimeStamp failed because one or more objects access this column.

However, it looks like this statistic 'Stat_a41cbd7f968a4cba86199c960f6f7c3a' is not present in my sys.stats table, which is very odd.

Is there any other location it might be defined?

Edit: There isn't a single entry in sys.stats named 'Stat_a41cbd7f968a4cba86199c960f6f7c3a'. In addition, I have never defined any custom statistics other than the automatic ones.

Answer 1

After reaching out to Azure support, I have managed to solve the issue.

Part of the support engineer's answer included the following:

I've reviewed internal telemetry and can confirm that the statistic listed in the error does not exist. This is likely a compute-node-level statistic that wasn't cleaned up properly.

I was able to confirm and fix this issue by doing the following steps:

1. Run a CTAS to create a copy of the table
2. Rename the previous table to something different (eg: ) and the new one to the original table name
3. DROP the old table

After that, the ALTER TABLE statement worked as expected.