//----------------------------------------------------------------------------
// Transform each aggregate in the MAV select list, to use the @OP column in
// order to calculate deleted rows correctly:
// COUNT(*) => SUM(@OP)
// COUNT(a) => SUM(IF (a IS NULL) THEN 0 ELSE @OP)
// SUM(a) => SUM(a * @OP)
// MIN(a) & MAX(a) => Special treatment (see handleDeltaMinMaxColumns()).
// AVG, STDDEV and VARIANCE are derived from other COUNT and SUM columns.
// They are removed from this select list to avoid divide by zero problems
// in case COUNT=0.
void MavRelRootBuilder::fixDeltaColumns(RelExpr *mvSelectTree,
NABoolean canSkipMinMax,
NABoolean wasFullDE)
{
// Get the MAV select list from the mvSelectTree.
CMPASSERT(mvSelectTree->getOperatorType() == REL_ROOT);
RelRoot *mavSelectRoot = (RelRoot *)mvSelectTree;
ItemExprList mavSelectList(mavSelectRoot->removeCompExprTree(), heap_);
ItemExprList newSelectList(heap_);
const NAString& opName = MavBuilder::getVirtualOpColumnName();
for (CollIndex i=0; i<mavSelectList.entries(); i++)
{
ItemExpr *selectListExpr = mavSelectList[i];
CMPASSERT(selectListExpr->getOperatorType() == ITM_RENAME_COL);
const NAString& colName =
((RenameCol*)selectListExpr)->getNewColRefName()->getColName();
ItemExpr *aggregateExpr = selectListExpr;
while ((aggregateExpr->getOperatorType() == ITM_RENAME_COL) ||
(aggregateExpr->getOperatorType() == ITM_CAST))
aggregateExpr = aggregateExpr->child(0);
// Assuming all aggregates are top-most functions as explained in the
// MV external spec.
ItemExpr *aggregateOperand = aggregateExpr->child(0);
ItemExpr *newExpr = NULL;
if (!aggregateExpr->containsAnAggregate())
{
// Non-aggregate columns (group-by cols) are added unchanged.
}
else
switch (aggregateExpr->getOperatorType())
{
case ITM_COUNT_NONULL:
// COUNT(a) => SUM(IF (a IS NULL) THEN 0 ELSE @OP)
newExpr = new(heap_)
Aggregate(ITM_SUM, new(heap_)
Case(NULL, new(heap_)
IfThenElse (new(heap_) UnLogic(ITM_IS_NULL, aggregateOperand),
new(heap_) SystemLiteral(0),
new(heap_) ColReference(new(heap_)
ColRefName(opName)))));
selectListExpr->child(0) = newExpr;
break;
case ITM_COUNT:
// COUNT(*) => SUM(@OP)
newExpr = new(heap_)
Aggregate(ITM_SUM,
new(heap_) ColReference(new(heap_) ColRefName(opName)));
selectListExpr->child(0) = newExpr;
break;
case ITM_SUM:
// SUM(a) => SUM(a * @OP)
newExpr = new(heap_)
BiArith(ITM_TIMES,
aggregateOperand,
new(heap_) ColReference(new(heap_) ColRefName(opName)));
aggregateExpr->child(0) = newExpr;
break;
case ITM_MIN:
case ITM_MAX:
// Handle Min/Max if not all deltas are INSERT ONLY.
if (!canSkipMinMax)
handleDeltaMinMaxColumns(aggregateExpr, colName, newSelectList, wasFullDE);
// Add the SYS_DELTA Min/Max aggregate as is.
break;
case ITM_AVG:
case ITM_DIVIDE:
case ITM_VARIANCE:
case ITM_STDDEV:
// Remove these expressions from the select list.
selectListExpr = NULL;
break;
default:
// A new type of aggregate?
CMPASSERT(FALSE);
break;
}
if (selectListExpr!=NULL)
newSelectList.insert(selectListExpr);
}
ItemExpr *selList = newSelectList.convertToItemExpr();
mavSelectRoot->addCompExprTree(selList);
mavSelectList.clear(); // Don't delete all the entries from the Dtor.
} // MavRelRootBuilder::fixDeltaColumns()
