//---------------------------------------------------------------------------
// @function:
// CGroupExpression::CleanupContexts
//
// @doc:
// Destroy stored cost contexts in hash table
//
//---------------------------------------------------------------------------
void
CGroupExpression::CleanupContexts()
{
// need to suspend cancellation while cleaning up
{
CAutoSuspendAbort asa;
ShtIter shtit(m_sht);
CCostContext *pcc = NULL;
while (NULL != pcc || shtit.FAdvance())
{
if (NULL != pcc)
{
pcc->Release();
}
// iter's accessor scope
{
ShtAccIter shtitacc(shtit);
if (NULL != (pcc = shtitacc.Pt()))
{
shtitacc.Remove(pcc);
}
}
}
}
#ifdef GPOS_DEBUG
CWorker::PwrkrSelf()->ResetTimeSlice();
#endif // GPOS_DEBUG
}
//---------------------------------------------------------------------------
// @function:
// CGroupExpression::PccInsertBest
//
// @doc:
// Insert given context in hash table only if a better context
// does not already exist,
// return the context that is kept in hash table
//
//---------------------------------------------------------------------------
CCostContext *
CGroupExpression::PccInsertBest
(
CCostContext *pcc
)
{
GPOS_ASSERT(NULL != pcc);
COptimizationContext *poc = pcc->Poc();
const ULONG ulOptReq = pcc->UlOptReq();
// remove existing cost context, if any
CCostContext *pccExisting = PccRemove(poc, ulOptReq);
CCostContext *pccKept = NULL;
// compare existing context with given context
if (NULL == pccExisting || pcc->FBetterThan(pccExisting))
{
// insert new context
pccKept = PccInsert(pcc);
GPOS_ASSERT(pccKept == pcc);
if (NULL != pccExisting)
{
if (pccExisting == poc->PccBest())
{
// change best cost context of the corresponding optimization context
poc->SetBest(pcc);
}
pccExisting->Release();
}
}
else
{
// re-insert existing context
pcc->Release();
pccKept = PccInsert(pccExisting);
GPOS_ASSERT(pccKept == pccExisting);
}
return pccKept;
}
//---------------------------------------------------------------------------
// @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;
}