//---------------------------------------------------------------------------
// @function:
// CGroupExpression::PccComputeCost
//
// @doc:
// Compute and store expression's cost under a given context;
// the function returns the cost context containing the computed cost
//
//---------------------------------------------------------------------------
CCostContext *
CGroupExpression::PccComputeCost
(
IMemoryPool *pmp,
COptimizationContext *poc,
ULONG ulOptReq,
DrgPoc *pdrgpoc, // array of child contexts
BOOL fPruned, // is created cost context pruned based on cost bound
CCost costLowerBound // lower bound on the cost of plan carried by cost context
)
{
GPOS_ASSERT(NULL != poc);
GPOS_ASSERT_IMP(!fPruned, NULL != pdrgpoc);
if (!fPruned && !FValid(pmp, poc, pdrgpoc))
{
return NULL;
}
// check if the same cost context is already created for current group expression
if (FCostContextExists(poc, pdrgpoc))
{
return NULL;
}
poc->AddRef();
this->AddRef();
CCostContext *pcc = GPOS_NEW(pmp) CCostContext(pmp, poc, ulOptReq, this);
BOOL fValid = true;
// computing cost
pcc->SetState(CCostContext::estCosting);
if (!fPruned)
{
if (NULL != pdrgpoc)
{
pdrgpoc->AddRef();
}
pcc->SetChildContexts(pdrgpoc);
fValid = pcc->FValid(pmp);
if (fValid)
{
CCost cost = CostCompute(pmp, pcc);
pcc->SetCost(cost);
}
GPOS_ASSERT_IMP(COptCtxt::FAllEnforcersEnabled(), fValid &&
"Cost context carries an invalid plan");
}
else
{
pcc->SetPruned();
pcc->SetCost(costLowerBound);
}
pcc->SetState(CCostContext::estCosted);
if (fValid)
{
return PccInsertBest(pcc);
}
pcc->Release();
// invalid cost context
return NULL;
}
