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Diving Into the Window Spool Operator

Hugo Kornelis continues a series on execution plan operators:

The Window Spool operator is one of the four spool operators that SQL Server supports. Like other spool operators, it retains a copy of data it receives and can then return those rows as often as needed. The specific functionality of the Window Spool operator allows it to replay rows within a window, as defined in a ROWS or RANGE specification of an OVER clause.

Read on to see how these work, as well as a few differences from their spool brethren.