SQL Server Execution Plans - Red Gate Software

Chapter 2: Graphical Execution Plans for Basic Queries
Most of the time in this chapter, the value for both the rebinds and rewinds has been
zero, but for the Sort operator example, a little earlier, we saw that there was one actual
rebind and zero actual rewinds. Figure 2.33 shows the relevant section of the Properties
page for that operator.
Figure 2.33
In order to understand what these values mean, we need some background. Whenever
a physical operator, such as the Sort operator in an execution plan occurs, three things
happen.
• First, the physical operator is initialized and any required data structures are set up.
This is called the Init() method. In all cases, this happens once for an operator,
although it is possible for it to happen many times.
• Second, the physical operator gets (or receives) the rows of data that it is to act on. This
is called the GetNext() method. Depending on the type of operator, it may receive
none, or many GetNext() calls.
• Third, once the operator has performed its function, it needs to clean itself up and
shut itself down. This is called the Close() method. A physical operator only ever
receives a single Close() call.
A rebind or rewind is a count of the number of times the Init() method is called by an
operator. A rebind and a rewind both count the number of times the Init() method is
called, but do so under different circumstances.
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