// requires: caseForOuterJoins corresponds the slot "slotNum"
// effects: Adds a WhenThen corresponding to child to caseForOuterJoins.
private void AddCaseForOuterJoins(CaseStatement caseForOuterJoins, CqlBlock child, int slotNum, CqlIdentifiers identifiers)
{
// Determine the cells that the slot comes from
// and make an OR expression, e.g., WHEN _from0 or _from2 or ... THEN child[slotNum]
ProjectedSlot childSlot = child.SlotValue(slotNum);
ConstantProjectedSlot constantSlot = childSlot as ConstantProjectedSlot;
if (constantSlot != null && constantSlot.CellConstant.IsNull())
{
// NULL being generated by a child - don't need to project
return;
}
BoolExpression originBool = BoolExpression.False;
for (int i = 0; i < NumBoolSlots; i++)
{
int boolSlotNum = BoolIndexToSlot(i);
if (child.IsProjected(boolSlotNum))
{
// OR it to the expression
QualifiedCellIdBoolean boolExpr = new QualifiedCellIdBoolean(child, identifiers, i);
originBool = BoolExpression.CreateOr(originBool, BoolExpression.CreateLiteral(boolExpr, RightDomainMap));
}
}
// Qualify the slotNum with the child.CqlAlias for the THEN
QualifiedSlot slot = child.QualifySlotWithBlockAlias(slotNum);
caseForOuterJoins.AddWhenThen(originBool, slot);
}
