Eager spool for update and delete on partitioned table
The eager spool has to do with the size of data you're deleting.

In this case, you're updating a large quantity of rows on a table with several indexes. You're also updating a field that's covered by a lot of nonclustered indexes, and SQL Server has to update all of those indexes as well.

To avoid this operation, update less rows (as a percentage of the table) or index the table less heavily.