C++ CBitSet::Size方法代码示例

//---------------------------------------------------------------------------
//	@function:
//		CJoinOrderDP::PexprBuildPred
//
//	@doc:
//		Build predicate connecting the two given sets
//
//---------------------------------------------------------------------------
CExpression *
CJoinOrderDP::PexprBuildPred
	(
	CBitSet *pbsFst,
	CBitSet *pbsSnd
	)
{
	// collect edges connecting the given sets
	CBitSet *pbsEdges = GPOS_NEW(m_mp) CBitSet(m_mp);
	CBitSet *pbs = GPOS_NEW(m_mp) CBitSet(m_mp, *pbsFst);
	pbs->Union(pbsSnd);

	for (ULONG ul = 0; ul < m_ulEdges; ul++)
	{
		SEdge *pedge = m_rgpedge[ul];
		if (
			pbs->ContainsAll(pedge->m_pbs) &&
			!pbsFst->IsDisjoint(pedge->m_pbs) &&
			!pbsSnd->IsDisjoint(pedge->m_pbs)
			)
		{
#ifdef GPOS_DEBUG
		BOOL fSet =
#endif // GPOS_DEBUG
			pbsEdges->ExchangeSet(ul);
			GPOS_ASSERT(!fSet);
		}
	}
	pbs->Release();

	CExpression *pexprPred = NULL;
	if (0 < pbsEdges->Size())
	{
		CExpressionArray *pdrgpexpr = GPOS_NEW(m_mp) CExpressionArray(m_mp);
		CBitSetIter bsi(*pbsEdges);
		while (bsi.Advance())
		{
			ULONG ul = bsi.Bit();
			SEdge *pedge = m_rgpedge[ul];
			pedge->m_pexpr->AddRef();
			pdrgpexpr->Append(pedge->m_pexpr);
		}

		pexprPred = CPredicateUtils::PexprConjunction(m_mp, pdrgpexpr);
	}

	pbsEdges->Release();
	return pexprPred;
}

//---------------------------------------------------------------------------
//	@function:
//		CPhysical::PppsRequiredPushThruNAry
//
//	@doc:
//		Helper for pushing required partition propagation to the children of
//		an n-ary operator
//
//---------------------------------------------------------------------------
CPartitionPropagationSpec *
CPhysical::PppsRequiredPushThruNAry
	(
	IMemoryPool *mp,
	CExpressionHandle &exprhdl,
	CPartitionPropagationSpec *pppsReqd,
	ULONG child_index
	)
{
	GPOS_ASSERT(NULL != pppsReqd);


	CPartIndexMap *ppimReqd = pppsReqd->Ppim();
	CPartFilterMap *ppfmReqd = pppsReqd->Ppfm();

	ULongPtrArray *pdrgpul = ppimReqd->PdrgpulScanIds(mp);

	CPartIndexMap *ppimResult = GPOS_NEW(mp) CPartIndexMap(mp);
	CPartFilterMap *ppfmResult = GPOS_NEW(mp) CPartFilterMap(mp);

	const ULONG ulPartIndexIds = pdrgpul->Size();
	const ULONG arity = exprhdl.UlNonScalarChildren();

	// iterate over required part index ids and decide which ones to push to the outer
	// and which to the inner side of the n-ary op
	for (ULONG ul = 0; ul < ulPartIndexIds; ul++)
	{
		ULONG part_idx_id = *((*pdrgpul)[ul]);
		GPOS_ASSERT(ppimReqd->Contains(part_idx_id));

		CBitSet *pbsPartConsumer = GPOS_NEW(mp) CBitSet(mp);
		for (ULONG ulChildIdx = 0; ulChildIdx < arity; ulChildIdx++)
		{
			if (exprhdl.GetRelationalProperties(ulChildIdx)->Ppartinfo()->FContainsScanId(part_idx_id))
			{
				(void) pbsPartConsumer->ExchangeSet(ulChildIdx);
			}
		}

		if (arity == pbsPartConsumer->Size() &&
			COperator::EopPhysicalSequence == exprhdl.Pop()->Eopid() &&
			(*(exprhdl.Pgexpr()))[0]->FHasCTEProducer())
		{
			GPOS_ASSERT(2 == arity);

			// this is a part index id that comes from both sides of a sequence
			// with a CTE producer on the outer side, so pretend that part index
			// id is not defined the inner sides
			pbsPartConsumer->ExchangeClear(1);
		}

		if (!FCanPushPartReqToChild(pbsPartConsumer, child_index))
		{
			// clean up
			pbsPartConsumer->Release();

			continue;
		}

		// clean up
		pbsPartConsumer->Release();

		CPartKeysArray *pdrgppartkeys = exprhdl.GetRelationalProperties(child_index)->Ppartinfo()->PdrgppartkeysByScanId(part_idx_id);
		GPOS_ASSERT(NULL != pdrgppartkeys);
		pdrgppartkeys->AddRef();

		// push requirements to child node
		ppimResult->AddRequiredPartPropagation(ppimReqd, part_idx_id, CPartIndexMap::EppraPreservePropagators, pdrgppartkeys);

		// check if there is a filter on the part index id and propagate that further down
		if (ppfmReqd->FContainsScanId(part_idx_id))
		{
			CExpression *pexpr = ppfmReqd->Pexpr(part_idx_id);
			// if the current child is inner child and the predicate is IsNull check and the parent is outer join,
			// don't push IsNull check predicate to the partition filter.
			// for all the other cases, push the filter down.
			if (!(1 == child_index &&
				CUtils::FScalarNullTest(pexpr) &&
				CUtils::FPhysicalOuterJoin(exprhdl.Pop()))
				)
			{
				pexpr->AddRef();
				ppfmResult->AddPartFilter(mp, part_idx_id, pexpr, NULL /*stats */);
			}
		}
	}

	pdrgpul->Release();

	return GPOS_NEW(mp) CPartitionPropagationSpec(ppimResult, ppfmResult);
}

//---------------------------------------------------------------------------
//	@function:
//		CJoinOrderDP::PexprBestJoinOrder
//
//	@doc:
//		find best join order for a given set of elements;
//
//---------------------------------------------------------------------------
CExpression *
CJoinOrderDP::PexprBestJoinOrder
	(
	CBitSet *pbs
	)
{
	GPOS_CHECK_STACK_SIZE;
	GPOS_CHECK_ABORT;

	GPOS_ASSERT(NULL != pbs);

	// start by looking-up cost in the DP map
	CExpression *pexpr = PexprLookup(pbs);

	if (pexpr == m_pexprDummy)
	{
		// no join order could be created
		return NULL;
	}

	if (NULL != pexpr)
	{
		// join order is found by looking up map
		return pexpr;
	}

	// find maximal covered subset
	CBitSet *pbsCovered = PbsCovered(pbs);
	if (0 == pbsCovered->Size())
	{
		// set is not covered, return a cross product
		pbsCovered->Release();

		return PexprCross(pbs);
	}

	if (!pbsCovered->Equals(pbs))
	{
		// create a cross product for uncovered subset
		CBitSet *pbsUncovered = GPOS_NEW(m_mp) CBitSet(m_mp, *pbs);
		pbsUncovered->Difference(pbsCovered);
		CExpression *pexprResult =
			PexprJoinCoveredSubsetWithUncoveredSubset(pbs, pbsCovered, pbsUncovered);
		pbsCovered->Release();
		pbsUncovered->Release();

		return pexprResult;
	}
	pbsCovered->Release();

	// if set has size 2, there is only one possible solution
	if (2 == pbs->Size())
	{
		return PexprJoin(pbs);
	}

	// otherwise, compute best join order using dynamic programming
	CExpression *pexprBestJoinOrder = PexprBestJoinOrderDP(pbs);
	if (pexprBestJoinOrder == m_pexprDummy)
	{
		// no join order could be created
		return NULL;
	}

	return pexprBestJoinOrder;
}