SQL Server query Plan Series-logical operators and physical operators

1. Logical operator

two。 Physical operator

1) the Init (): Init () method causes a physical operator to complete its own initialization and create any required data structures. Although a physical operator can receive many Init () calls, generally speaking, a physical operator only receives an Init ().

3) Close (): the Close () party causes a physical operation to perform some cleanup operations and close itself. A physical operator can receive only one Close () call.

Considerations related to physical operators

2) the ActualRebinds and ActualRewinds that appear in the Showplan output refer to the number of times the Init () method was called. Unless an operator is an internal source of circular joins (Loop Join), ActualRebinds is 1 and ActualRewinds is 0. If an operator is the inner source of a loop connection, the sum of rebinds and rewinds should be equal to the number of lines that the loop connects to the outside source. Rebinding means that the internal source must be reevaluated when one or more of the relevant parameters in the connection change. Rewinding means that the result before the expert source can be reused when the relevant parameters are not changed. ActualRebinds and ActualRewinds appear in the Showplan output resulting from the SETSTATISTICS XML ON setting. They are populated only in Nonclustered Index Spool, Remote Query, Rows CountSpool, Sort, Table Spool, and Table-valuedFunction operations. When the StartupExpression property is set to TRUE, ActualRebinds and ActualRewinds may be populated in the Assert and Filter operators. When ActualRebinds and ActualRewinds appear in XMLShowplan, they can be compared to EstimateRebinds and EstimateRewinds. When they do not exist, EstimateRows can be compared to ActualRows. Note that when they do not exist, actual rebinds and actualrewinds are displayed as 0 in the actual graphic Showplan output.