Defines the interface for passing down a relational TOP operation to the DSII. More...
Inherited by DSIExtAbstractTopHandler.
Public Member Functions
< DSIExtResultSet >
|Passdown (AETop *in_node)=0|
|Pass down the given TOP N operation. |
Protected Member Functions
Defines the interface for passing down a relational TOP operation to the DSII.
A relational TOP operation limits the rows returned in a query result set to a specified number of rows. When TOP is used in conjunction with the ORDER BY clause, the result set is limited to the first N number of ordered rows; otherwise, it returns the first N number of rows in an undefined order.
Simba SQLEngine attempts to pass down the operand before attempting to pass down TOP. In other words, the handler to perform TOP pass-down will never be invoked if the operand is not passed down successfully.
A relational TOP operation can be either TOP N or TOP N PERCENT.
Pass down the given TOP N operation.
An implementation should ensure that this method returns the table representing the TOP N result if the operation is successfully passed down. Otherwise, it should return NULL and in_node remains intact.
|in_node||The TOP operation node. Cannot be NULL. (NOT OWN)|
Implemented in DSIExtAbstractTopHandler.