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can you also explain how a row level lock can be requested in macro? and some situations where Optimizer determines for a table level lock?

Thanks forum.

We stumbled upon this by accident. We have a query that runs much faster when a group by is added to a derived table when one of the columns in the derived table is the result of a cast/concatenation operation.

The first query/explain posted below has the group by in the derived table. It shows the cast/concatenation being resolved when the derived table is materialized in step 2 in the EXPLAIN. Result is 761 rows and I assume 761 resolutions of the cast/concatenation. The group by does not eliminate any dups.