Calculating Extent and Starting and Ending Positions of a Value

To manage the display of the result set retrieved by a CompoundCursor, you sometimes need to know the extent of its child Cursor components. You might also want to know the position at which the current value of a child Cursor starts in its parent CompoundCursor. You might want to know the span of the current value of a child Cursor. The span is the number of positions of the parent Cursor that the current value of the child Cursor occupies. You can calculate the span by subtracting the starting position of the value from its ending position and subtracting 1.

Before you can get the extent of a Cursor or get the starting or ending positions of a value in its parent Cursor, you must specify that you want Oracle OLAP to calculate the extent or those positions. To specify the performance of those calculations, you use methods on the CursorSpecification for the Cursor.

Example 9-10 specifies calculating the extent of a Cursor. The example uses the CursorManagerSpecification from Example 9-9.

Example 9-10 Specifying the Calculation of the Extent of a Cursor

CompoundCursorSpecification rootCursorSpec =
(CompoundCursorSpecification) cursorMngrSpec.getRootCursorSpecification();
rootCursorSpec.setExtentCalculationSpecified(true);

You can use methods on a CursorSpecification to determine whether the CursorSpecification specifies the calculation of the extent of a Cursor as in the following example.

boolean isSet = rootCursorSpec.isExtentCalculationSpecified();

Example 9-11 specifies calculating the starting and ending positions of the current value of a child Cursor in its parent Cursor. The example uses the CursorManagerSpecification from Example 9-9.

Example 9-11 Specifying the Calculation of Starting and Ending Positions in a Parent

CompoundCursorSpecification rootCursorSpec =
(CompoundCursorSpecification) cursorMngrSpec.getRootCursorSpecification();

// Get the List of CursorSpecification objects for the outputs. 
// Iterate through the list, specifying the calculation of the extent
// for each output CursorSpecification. 
Iterator iterOutputSpecs = rootCursorSpec.getOutputs().iterator();
ValueCursorSpecification valCursorSpec = (ValueCursorSpecification)
                                          iterOutputSpecs.next();
while(iterOutputSpecs.hasNext()) {
  valCursorSpec.setParentStartCalculationSpecified(true);
  valCursorSpec.setParentEndCalculationSpecified(true);
  valCursorSpec = (ValueCursorSpecification) iterOutputSpecs.next();
}

You can use methods on a CursorSpecification to determine whether the CursorSpecification specifies the calculation of the starting or ending positions of the current value of a child Cursor in its parent Cursor, as in the following example.

boolean isSet;
Iterator iterOutputSpecs = rootCursorSpec.getOutputs().iterator();
ValueCursorSpecification valCursorSpec = (ValueCursorSpecification)
                                          iterOutputSpecs.next();
while(iterOutputSpecs.hasNext()) {
  isSet = valCursorSpec.isParentStartCalculationSpecified();
  isSet = valCursorSpec.isParentEndCalculationSpecified();
  valCursorSpec = (ValueCursorSpecification) iterOutputSpecs.next();
}

Example 9-12 determines the span of the positions in a parent CompoundCursor of the current value of a child Cursor for two of the outputs of the CompoundCursor. The example uses the salesAmountsForSelections Source from Example 9-8.

The example gets the starting and ending positions of the current values of the time and product selections and then calculates the span of those values in the parent Cursor. The parent is the root CompoundCursor. The TransactionProvider is tp, the DataProvider is dp, and output is a PrintWriter.

Example 9-12 Calculating the Span of the Positions in the Parent of a Value

Source salesAmountsForSelections = salesAmount.join(customerSel)
                                              .join(productSel);
                                              .join(timeSel);
                                              .join(channelSel);
                                              .join(promotionSel);
try{
  tp.prepareCurrentTransaction();
}
catch(NotCommittableException e){
  output.println("Caught exception " + e + ".");
}
tp.commitCurrentTransaction();

// Create a CursorManagerSpecification for salesAmountsForSelections
CursorManagerSpecification cursorMngrSpec =
     dp.createCursorManagerSpecification(salesAmountsForSelections);

 // Get the root CursorSpecification from the CursorManagerSpecification.
CompoundCursorSpecification rootCursorSpec =
(CompoundCursorSpecification) cursorMngrSpec.getRootCursorSpecification();
// Get the CursorSpecification objects for the outputs
List outputSpecs = rootCursorSpec.getOutputs();
ValueCursorSpecification timeSelValCSpec = 
 (ValueCursorSpecification) outputSpecs.get(2); \\ output for time
ValueCursorSpecification prodSelValCSpec = 
 (ValueCursorSpecification) outputSpecs.get(3)  \\ output for product

// Specify the calculation of the starting and ending positions
timeSelValCSpec.setParentStartCalculationSpecified(true);
timeSelValCSpec.setParentEndCalculationSpecified(true);
prodSelValCSpec.setParentStartCalculationSpecified(true);
prodSelValCSpec.setParentEndCalculationSpecified(true);

// Create the CursorManager and the Cursor
SpecifiedCursorManager cursorMngr = dp.createCursorManager(cursorMngrSpec);
CompoundCursor cursor = (CompoundCursor) cursorMngr.createCursor();

// Get the child Cursor objects
ValueCursor baseValCursor = cursor.getValueCursor();
List outputs = cursor.getOutputs();
ValueCursor promoSelVals = (ValueCursor) outputs.get(0);
ValueCursor chanSelVals = (ValueCursor) outputs.get(1);
ValueCursor timeSelVals = (ValueCursor) outputs.get(2);
ValueCursor custSelVals = (ValueCursor) outputs.get(3);
ValueCursor prodSelVals = (ValueCursor) outputs.get(4);

// Set the position of the root CompoundCursor
cursor.setPosition(15);
/*
 * Get the values at the current position and determine the span
 * of the values of the time and product outputs.
 */ 
output.print(promoSelVals.getCurrentValue() + ", ");
output.print(chanSelVals.getCurrentValue() + ", ");
output.print(timeSelVals.getCurrentValue() + ", ");
output.print(custSelVals.getCurrentValue() + ", ");
output.print(prodSelVals.getCurrentValue() + ", ");
output.println(baseValCursor.getCurrentValue());

// Determine the span of the values of the two fastest varying outputs
int span;
span = (prodSelVals.getParentEnd() - prodSelVals.getParentStart()) -1);
output.println("The span of " + prodSelVals.getCurrentValue() +
" at the current position is " + span + ".")
span = (timeSelVals.getParentEnd() - timeSelVals.getParentStart()) -1);
output.println("The span of " + timeSelVals.getCurrentValue() +
" at the current position is " + span + ".")
cursorMngr.close();

This example produces the following output.

Promotion total, Direct, 2000-Q1, Outerwear - Men, US, 9947221.50
The span of Outerwear - Men at the current position is 3.
The span of 2000-Q2 at the current position is 12.