/// <summary>
/// Given the slot (<paramref name="foundSlot" />) and its corresponding case statement (
/// <paramref
/// name="thisCaseStatement" />
/// ),
/// generates the slotinfos for the cql block producing the case statement.
/// </summary>
private SlotInfo[] CreateSlotInfosForCaseStatement(
bool[] parentRequiredSlots,
int foundSlot,
CqlBlock childBlock,
CaseStatement thisCaseStatement,
IEnumerable<WithRelationship> withRelationships)
{
var numSlotsAddedByChildBlock = childBlock.Slots.Count - TotalSlots;
var slotInfos = new SlotInfo[TotalSlots + numSlotsAddedByChildBlock];
for (var slotNum = 0; slotNum < TotalSlots; slotNum++)
{
var isProjected = childBlock.IsProjected(slotNum);
var isRequiredByParent = parentRequiredSlots[slotNum];
var slot = childBlock.SlotValue(slotNum);
var outputMember = GetOutputMemberPath(slotNum);
if (slotNum == foundSlot)
{
// We need a case statement instead for this slot that we
// are handling right now
Debug.Assert(isRequiredByParent, "Case result not needed by parent");
// Get a case statement with all slots replaced by aliases slots
var newCaseStatement = thisCaseStatement.DeepQualify(childBlock);
slot = new CaseStatementProjectedSlot(newCaseStatement, withRelationships);
isProjected = true; // We are projecting this slot now
}
else if (isProjected && isRequiredByParent)
{
// We only alias something that is needed and is being projected by the child.
// It is a qualified slot into the child block.
slot = childBlock.QualifySlotWithBlockAlias(slotNum);
}
// For slots, if it is not required by the parent, we want to
// set the isRequiredByParent for this slot to be
// false. Furthermore, we do not want to introduce any "NULL
// AS something" at this stage for slots not being
// projected. So if the child does not project that slot, we
// declare it as not being required by the parent (if such a
// NULL was needed, it would have been pushed all the way
// down to a non-case block.
// Essentially, from a Case statement's parent perspective,
// it is saying "If you can produce a slot either by yourself
// or your children, please do. Otherwise, do not concoct anything"
var slotInfo = new SlotInfo(isRequiredByParent && isProjected, isProjected, slot, outputMember);
slotInfos[slotNum] = slotInfo;
}
for (var i = TotalSlots; i < TotalSlots + numSlotsAddedByChildBlock; i++)
{
var childAddedSlot = childBlock.QualifySlotWithBlockAlias(i);
slotInfos[i] = new SlotInfo(true, true, childAddedSlot, childBlock.MemberPath(i));
}
return slotInfos;
}
// effects: Generates a SlotInfo object for a slot of a join node. It
// uses the type of the join operation (opType), whether the slot is
// required by the parent or not (isRequiredSlot), the children of
// this node (children) and the number of the slotNum
private SlotInfo GetJoinSlotInfo(
CellTreeOpType opType, bool isRequiredSlot,
List <CqlBlock> children, int slotNum, CqlIdentifiers identifiers)
{
if (false == isRequiredSlot)
{
// The slot will not be used. So we can set the projected slot to be null
var unrequiredSlotInfo = new SlotInfo(false, false, null, GetMemberPath(slotNum));
return(unrequiredSlotInfo);
}
// For a required slot, determine the child who is contributing to this value
var childDefiningSlot = -1;
CaseStatement caseForOuterJoins = null;
for (var childNum = 0; childNum < children.Count; childNum++)
{
var child = children[childNum];
if (false == child.IsProjected(slotNum))
{
continue;
}
// For keys, we can pick any child block. So the first
// one that we find is fine as well
if (IsKeySlot(slotNum))
{
childDefiningSlot = childNum;
break;
}
else if (opType == CellTreeOpType.IJ)
{
// For Inner Joins, most of the time, the entries will be
// the same in all the children. However, in some cases,
// we will end up with NULL in one child and an actual
// value in another -- we should pick up the actual value in that case
childDefiningSlot = GetInnerJoinChildForSlot(children, slotNum);
break;
}
else
{
// For LOJs, we generate a case statement if more than
// one child generates the value - until then we do not
// create the caseForOuterJoins object
if (childDefiningSlot != -1)
{
// We really need a case statement now
// We have the value being generated by another child
// We need to fetch the variable from the appropriate child
Debug.Assert(false == IsBoolSlot(slotNum), "Boolean slots cannot come from two children");
if (caseForOuterJoins == null)
{
var outputMember = GetMemberPath(slotNum);
caseForOuterJoins = new CaseStatement(outputMember);
// Add the child that we had not added in the first shot
AddCaseForOuterJoins(caseForOuterJoins, children[childDefiningSlot], slotNum, identifiers);
}
AddCaseForOuterJoins(caseForOuterJoins, child, slotNum, identifiers);
}
childDefiningSlot = childNum;
}
}
var memberPath = GetMemberPath(slotNum);
ProjectedSlot slot = null;
// Generate the slot value -- case statement slot, or a qualified slot or null or false.
// If case statement slot has nothing, treat it as null/empty.
if (caseForOuterJoins != null &&
(caseForOuterJoins.Clauses.Count > 0 || caseForOuterJoins.ElseValue != null))
{
caseForOuterJoins.Simplify();
slot = new CaseStatementProjectedSlot(caseForOuterJoins, null);
}
else if (childDefiningSlot >= 0)
{
slot = children[childDefiningSlot].QualifySlotWithBlockAlias(slotNum);
}
else
{
// need to produce output slot, but don't have a value
// output NULL for fields or False for bools
if (IsBoolSlot(slotNum))
{
slot = new BooleanProjectedSlot(BoolExpression.False, identifiers, SlotToBoolIndex(slotNum));
}
else
{
slot = new ConstantProjectedSlot(Domain.GetDefaultValueForMemberPath(memberPath, GetLeaves(), ViewgenContext.Config));
}
}
// We need to ensure that _from variables are never null since
// view generation uses 2-valued boolean logic.
// They can become null in outer joins. We compensate for it by
// adding AND NOT NULL condition on boolean slots coming from outer joins.
var enforceNotNull = IsBoolSlot(slotNum) &&
((opType == CellTreeOpType.LOJ && childDefiningSlot > 0) ||
opType == CellTreeOpType.FOJ);
// We set isProjected to be true since we have come up with some value for it
var slotInfo = new SlotInfo(true, true, slot, memberPath, enforceNotNull);
return(slotInfo);
}
