C++ DrgPul类代码示例

//---------------------------------------------------------------------------
//	@function:
//		CLogicalUnion::PstatsDerive
//
//	@doc:
//		Derive statistics
//
//---------------------------------------------------------------------------
IStatistics *
CLogicalUnion::PstatsDerive
	(
	IMemoryPool *pmp,
	CExpressionHandle &exprhdl,
	DrgPstat * // not used
	)
	const
{
	GPOS_ASSERT(Esp(exprhdl) > EspNone);

	// union is transformed into a group by over an union all
	// we follow the same route to compute statistics
	IStatistics *pstatsUnionAll = CLogicalUnionAll::PstatsDeriveUnionAll(pmp, exprhdl);

	// computed columns
	DrgPul *pdrgpulComputedCols = GPOS_NEW(pmp) DrgPul(pmp);

	IStatistics *pstats = CLogicalGbAgg::PstatsDerive
											(
											pmp,
											pstatsUnionAll,
											m_pdrgpcrOutput, // we group by the output columns
											pdrgpulComputedCols, // no computed columns for set ops
											NULL // no keys, use all grouping cols
											);

	// clean up
	pdrgpulComputedCols->Release();
	pstatsUnionAll->Release();

	return pstats;
}

//---------------------------------------------------------------------------
//	@function:
//		CLogicalGbAggDeduplicate::PstatsDerive
//
//	@doc:
//		Derive statistics
//
//---------------------------------------------------------------------------
IStatistics *
CLogicalGbAggDeduplicate::PstatsDerive
	(
	IMemoryPool *pmp,
	CExpressionHandle &exprhdl,
	DrgPstat * // not used
	)
	const
{
	GPOS_ASSERT(Esp(exprhdl) > EspNone);
	IStatistics *pstatsChild = exprhdl.Pstats(0);

	// extract computed columns
	DrgPul *pdrgpulComputedCols = GPOS_NEW(pmp) DrgPul(pmp);
	exprhdl.Pdpscalar(1 /*ulChildIndex*/)->PcrsDefined()->ExtractColIds(pmp, pdrgpulComputedCols);

	// construct bitset with keys of join child
	CBitSet *pbsKeys = GPOS_NEW(pmp) CBitSet(pmp);
	const ULONG ulKeys = m_pdrgpcrKeys->UlLength();
	for (ULONG ul = 0; ul < ulKeys; ul++)
	{
		CColRef *pcr = (*m_pdrgpcrKeys)[ul];
		pbsKeys->FExchangeSet(pcr->UlId());
	}

	IStatistics *pstats = CLogicalGbAgg::PstatsDerive(pmp, pstatsChild, Pdrgpcr(), pdrgpulComputedCols, pbsKeys);
	pbsKeys->Release();
	pdrgpulComputedCols->Release();

	return pstats;
}

//---------------------------------------------------------------------------
//	@function:
//		CLogical::PstatsDeriveDummy
//
//	@doc:
//		Derive dummy statistics
//
//---------------------------------------------------------------------------
IStatistics *
CLogical::PstatsDeriveDummy
	(
	IMemoryPool *pmp,
	CExpressionHandle &exprhdl,
	CDouble dRows
	)
	const
{
	GPOS_CHECK_ABORT;

	// return a dummy stats object that has a histogram for every
	// required-stats column
	GPOS_ASSERT(Esp(exprhdl) > EspNone);
	CReqdPropRelational *prprel = CReqdPropRelational::Prprel(exprhdl.Prp());
	CColRefSet *pcrs = prprel->PcrsStat();
	DrgPul *pdrgpulColIds = GPOS_NEW(pmp) DrgPul(pmp);
	pcrs->ExtractColIds(pmp, pdrgpulColIds);

	IStatistics *pstats = CStatistics::PstatsDummy(pmp, pdrgpulColIds, dRows);

	// clean up
	pdrgpulColIds->Release();

	return pstats;
}

//---------------------------------------------------------------------------
//	@function:
//		CLogicalConstTableGet::PstatsDerive
//
//	@doc:
//		Derive statistics
//
//---------------------------------------------------------------------------
IStatistics *
CLogicalConstTableGet::PstatsDerive
	(
	IMemoryPool *pmp,
	CExpressionHandle &exprhdl,
	DrgPstat * // not used
	)
	const
{
	GPOS_ASSERT(Esp(exprhdl) > EspNone);
	CReqdPropRelational *prprel = CReqdPropRelational::Prprel(exprhdl.Prp());
	CColRefSet *pcrs = prprel->PcrsStat();
	DrgPul *pdrgpulColIds = GPOS_NEW(pmp) DrgPul(pmp);
	pcrs->ExtractColIds(pmp, pdrgpulColIds);
	DrgPul *pdrgpulColWidth = CUtils::Pdrgpul(pmp, m_pdrgpcrOutput);

	IStatistics *pstats = CStatistics::PstatsDummy
										(
										pmp,
										pdrgpulColIds,
										pdrgpulColWidth,
										m_pdrgpdrgpdatum->UlLength()
										);

	// clean up
	pdrgpulColIds->Release();
	pdrgpulColWidth->Release();

	return pstats;
}

//---------------------------------------------------------------------------
//	@function:
//		CPhysicalUnionAll::PdshashedDerive
//
//	@doc:
//		Derive hashed distribution from child hashed distributions
//
//---------------------------------------------------------------------------
CDistributionSpecHashed *
CPhysicalUnionAll::PdshashedDerive
	(
	IMemoryPool *pmp,
	CExpressionHandle &exprhdl
	)
	const
{
	BOOL fSuccess = true;
	const ULONG ulArity = exprhdl.UlArity();

	// (1) check that all children deliver a hashed distribution that satisfies their input columns
	for (ULONG ulChild = 0; fSuccess && ulChild < ulArity; ulChild++)
	{
		CDistributionSpec *pdsChild = exprhdl.Pdpplan(ulChild)->Pds();
		CDistributionSpec::EDistributionType edtChild = pdsChild->Edt();
		fSuccess =  (CDistributionSpec::EdtHashed == edtChild) && pdsChild->FSatisfies((*m_pdrgpds)[ulChild]);
	}

	if (!fSuccess)
	{
		// a child does not deliver hashed distribution
		return NULL;
	}

	// (2) check that child hashed distributions map to the same output columns

	// map outer child hashed distribution to corresponding UnionAll column positions
	DrgPul *pdrgpulOuter = PdrgpulMap(pmp, CDistributionSpecHashed::PdsConvert(exprhdl.Pdpplan(0 /*ulChildIndex*/)->Pds())->Pdrgpexpr(), 0/*ulChildIndex*/);
	if (NULL == pdrgpulOuter)
	{
		return NULL;
	}

	DrgPul *pdrgpulChild = NULL;
	for (ULONG ulChild = 1; fSuccess && ulChild < ulArity; ulChild++)
	{
		pdrgpulChild = PdrgpulMap(pmp, CDistributionSpecHashed::PdsConvert(exprhdl.Pdpplan(ulChild)->Pds())->Pdrgpexpr(), ulChild);

		// match mapped column positions of current child with outer child
		fSuccess = (NULL != pdrgpulChild) && FEqual(pdrgpulOuter, pdrgpulChild);
		CRefCount::SafeRelease(pdrgpulChild);
	}

	CDistributionSpecHashed *pdsOutput = NULL;
	if (fSuccess)
	{
		pdsOutput = PdsMatching(pmp, pdrgpulOuter);
	}

	pdrgpulOuter->Release();

	return pdsOutput;
}

//---------------------------------------------------------------------------
//	@function:
//		CDynamicPtrArrayTest::EresUnittest_PdrgpulSubsequenceIndexes
//
//	@doc:
//		Finding the first occurrences of the elements of the first array
//		in the second one.
//
//---------------------------------------------------------------------------
GPOS_RESULT
CDynamicPtrArrayTest::EresUnittest_PdrgpulSubsequenceIndexes()
{
	typedef CDynamicPtrArray<ULONG, CleanupNULL<ULONG> > DrgULONG;

	CAutoMemoryPool amp;
	IMemoryPool *pmp = amp.Pmp();

	// the array containing elements to look up
	DrgULONG *pdrgULONGLookup = GPOS_NEW(pmp) DrgULONG(pmp);

	// the array containing the target elements that will give the positions
	DrgULONG *pdrgULONGTarget = GPOS_NEW(pmp) DrgULONG(pmp);

	ULONG *pul1 = GPOS_NEW(pmp) ULONG(10);
	ULONG *pul2 = GPOS_NEW(pmp) ULONG(20);
	ULONG *pul3 = GPOS_NEW(pmp) ULONG(30);

	pdrgULONGLookup->Append(pul1);
	pdrgULONGLookup->Append(pul2);
	pdrgULONGLookup->Append(pul3);
	pdrgULONGLookup->Append(pul3);

	// since target is empty, there are elements in lookup with no match, so the function
	// should return NULL
	GPOS_ASSERT(NULL ==
			CDynamicPtrArrayUtils::PdrgpulSubsequenceIndexes(pmp, pdrgULONGLookup, pdrgULONGTarget));

	pdrgULONGTarget->Append(pul1);
	pdrgULONGTarget->Append(pul3);
	pdrgULONGTarget->Append(pul3);
	pdrgULONGTarget->Append(pul3);
	pdrgULONGTarget->Append(pul2);

	DrgPul *pdrgpulIndexes =
			CDynamicPtrArrayUtils::PdrgpulSubsequenceIndexes(pmp, pdrgULONGLookup, pdrgULONGTarget);
	GPOS_ASSERT(NULL != pdrgpulIndexes);
	GPOS_ASSERT(4 == pdrgpulIndexes->UlLength());
	GPOS_ASSERT(0 == *(*pdrgpulIndexes)[0]);
	GPOS_ASSERT(4 == *(*pdrgpulIndexes)[1]);
	GPOS_ASSERT(1 == *(*pdrgpulIndexes)[2]);
	GPOS_ASSERT(1 == *(*pdrgpulIndexes)[3]);

	GPOS_DELETE(pul1);
	GPOS_DELETE(pul2);
	GPOS_DELETE(pul3);
	pdrgpulIndexes->Release();
	pdrgULONGTarget->Release();
	pdrgULONGLookup->Release();

	return GPOS_OK;
}

//---------------------------------------------------------------------------
//	@function:
//		CPhysicalMotion::PppsRequired
//
//	@doc:
//		Compute required partition propagation of the n-th child
//
//---------------------------------------------------------------------------
CPartitionPropagationSpec *
CPhysicalMotion::PppsRequired
	(
	IMemoryPool *pmp,
	CExpressionHandle &exprhdl,
	CPartitionPropagationSpec *pppsRequired,
	ULONG 
#ifdef GPOS_DEBUG
	ulChildIndex
#endif // GPOS_DEBUG
	,
	DrgPdp *, //pdrgpdpCtxt,
	ULONG //ulOptReq
	)
{
	GPOS_ASSERT(0 == ulChildIndex);
	GPOS_ASSERT(NULL != pppsRequired);
	
	CPartIndexMap *ppimReqd = pppsRequired->Ppim();
	CPartFilterMap *ppfmReqd = pppsRequired->Ppfm();
	
	DrgPul *pdrgpul = ppimReqd->PdrgpulScanIds(pmp);
	
	CPartIndexMap *ppimResult = GPOS_NEW(pmp) CPartIndexMap(pmp);
	CPartFilterMap *ppfmResult = GPOS_NEW(pmp) CPartFilterMap(pmp);
	
	/// get derived part consumers
	CPartInfo *ppartinfo = exprhdl.Pdprel(0)->Ppartinfo();
	
	const ULONG ulPartIndexSize = pdrgpul->UlLength();
	
	for (ULONG ul = 0; ul < ulPartIndexSize; ul++)
	{
		ULONG ulPartIndexId = *((*pdrgpul)[ul]);

		if (!ppartinfo->FContainsScanId(ulPartIndexId))
		{
			// part index id does not exist in child nodes: do not push it below 
			// the motion
			continue;
		}

		ppimResult->AddRequiredPartPropagation(ppimReqd, ulPartIndexId, CPartIndexMap::EppraPreservePropagators);
		(void) ppfmResult->FCopyPartFilter(m_pmp, ulPartIndexId, ppfmReqd);
	}
		
	pdrgpul->Release();

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

//---------------------------------------------------------------------------
//	@function:
//		CColRef::Pdrgpul
//
//	@doc:
//		Extract array of colids from array of colrefs
//
//---------------------------------------------------------------------------
DrgPul *
CColRef::Pdrgpul
	(
	IMemoryPool *pmp,
	DrgPcr *pdrgpcr
	)
{
	DrgPul *pdrgpul = GPOS_NEW(pmp) DrgPul(pmp);
	const ULONG ulLen = pdrgpcr->UlLength();
	for (ULONG ul = 0; ul < ulLen; ul++)
	{
		CColRef *pcr = (*pdrgpcr)[ul];
		pdrgpul->Append(GPOS_NEW(pmp) ULONG(pcr->UlId()));
	}

	return pdrgpul;
}

//---------------------------------------------------------------------------
//	@function:
//		CCostContext::DRowsPerHost
//
//	@doc:
//		Return the number of rows per host
//
//---------------------------------------------------------------------------
CDouble
CCostContext::DRowsPerHost() const
{
	DOUBLE dRows = Pstats()->DRows().DVal();
	COptCtxt *poptctxt = COptCtxt::PoctxtFromTLS();
	const ULONG ulHosts = poptctxt->Pcm()->UlHosts();

	CDistributionSpec *pds =  Pdpplan()->Pds();
	if (CDistributionSpec::EdtHashed == pds->Edt())
	{
		CDistributionSpecHashed *pdshashed = CDistributionSpecHashed::PdsConvert(pds);
		DrgPexpr *pdrgpexpr = pdshashed->Pdrgpexpr();
		CColRefSet *pcrsUsed = CUtils::PcrsExtractColumns(m_pmp, pdrgpexpr);

		const CColRefSet *pcrsReqdStats = this->Poc()->Prprel()->PcrsStat();
		if (!pcrsReqdStats->FSubset(pcrsUsed))
		{
			// statistics not available for distribution columns, therefore
			// assume uniform distribution across hosts
			// clean up
			pcrsUsed->Release();

			return CDouble(dRows / ulHosts);
		}

		DrgPul *pdrgpul = GPOS_NEW(m_pmp) DrgPul(m_pmp);
		pcrsUsed->ExtractColIds(m_pmp, pdrgpul);
		pcrsUsed->Release();

		CStatisticsConfig *pstatsconf = poptctxt->Poconf()->Pstatsconf();
		CDouble dNDVs = CStatisticsUtils::DGroups(m_pmp, Pstats(), pstatsconf, pdrgpul, NULL /*pbsKeys*/);
		pdrgpul->Release();

		if (dNDVs < ulHosts)
		{
			// estimated number of distinct values of distribution columns is smaller than number of hosts.
			// We assume data is distributed across a subset of hosts in this case. This results in a larger
			// number of rows per host compared to the uniform case, allowing us to capture data skew in
			// cost computation
			return CDouble(dRows / dNDVs.DVal());
		}
	}

	return CDouble(dRows / ulHosts);
}

//---------------------------------------------------------------------------
//	@function:
//		CParseHandlerAgg::EndElement
//
//	@doc:
//		Invoked by Xerces to process a closing tag
//
//---------------------------------------------------------------------------
void
CParseHandlerAgg::EndElement
	(
	const XMLCh* const, // xmlszUri,
	const XMLCh* const xmlszLocalname,
	const XMLCh* const // xmlszQname
	)
{
	if(0 != XMLString::compareString(CDXLTokens::XmlstrToken(EdxltokenPhysicalAggregate), xmlszLocalname))
	{
		CWStringDynamic *pstr = CDXLUtils::PstrFromXMLCh(m_pphm->Pmm(), xmlszLocalname);
		GPOS_RAISE(gpdxl::ExmaDXL, gpdxl::ExmiDXLUnexpectedTag, pstr->Wsz());
	}
	
	// construct node from the created child nodes
	
	GPOS_ASSERT(5 == this->UlLength());
	
	CParseHandlerProperties *pphProp = dynamic_cast<CParseHandlerProperties *>((*this)[0]);
	CParseHandlerGroupingColList *pphGrpColList = dynamic_cast<CParseHandlerGroupingColList*>((*this)[1]);
	CParseHandlerProjList *pphPrL = dynamic_cast<CParseHandlerProjList*>((*this)[2]);
	CParseHandlerFilter *pphFilter = dynamic_cast<CParseHandlerFilter *>((*this)[3]);
	CParseHandlerPhysicalOp *pphChild = dynamic_cast<CParseHandlerPhysicalOp *>((*this)[4]);

	// set grouping cols list
	GPOS_ASSERT(NULL != pphGrpColList->PdrgpulGroupingCols());

	DrgPul *pdrgpul = pphGrpColList->PdrgpulGroupingCols();
	pdrgpul->AddRef();
	m_pdxlop->SetGroupingCols(pdrgpul);
	
	m_pdxln = GPOS_NEW(m_pmp) CDXLNode(m_pmp, m_pdxlop);	

	// set physical properties
	CParseHandlerUtils::SetProperties(m_pdxln, pphProp);

	// add children
	AddChildFromParseHandler(pphPrL);
	AddChildFromParseHandler(pphFilter);
	AddChildFromParseHandler(pphChild);
	
	// deactivate handler
	m_pphm->DeactivateHandler();
}

//---------------------------------------------------------------------------
//	@function:
//		CPhysicalUnionAll::PdrgpulMap
//
//	@doc:
//		Map given array of scalar identifier expressions to positions of
//		UnionAll input columns in the given child;
//		the function returns NULL if no mapping could be constructed
//
//---------------------------------------------------------------------------
DrgPul *
CPhysicalUnionAll::PdrgpulMap
	(
	IMemoryPool *pmp,
	DrgPexpr *pdrgpexpr,
	ULONG ulChildIndex
	)
	const
{
	GPOS_ASSERT(NULL != pdrgpexpr);

	DrgPcr *pdrgpcr = (*m_pdrgpdrgpcrInput)[ulChildIndex];
	const ULONG ulExprs = pdrgpexpr->UlLength();
	const ULONG ulCols = pdrgpcr->UlLength();
	DrgPul *pdrgpul = GPOS_NEW(pmp) DrgPul(pmp);
	for (ULONG ulExpr = 0; ulExpr < ulExprs; ulExpr++)
	{
		CExpression *pexpr = (*pdrgpexpr)[ulExpr];
		if (COperator::EopScalarIdent != pexpr->Pop()->Eopid())
		{
			continue;
		}
		const CColRef *pcr = CScalarIdent::PopConvert(pexpr->Pop())->Pcr();
		for (ULONG ulCol = 0; ulCol < ulCols; ulCol++)
		{
			if ((*pdrgpcr)[ulCol] == pcr)
			{
				pdrgpul->Append(GPOS_NEW(pmp) ULONG(ulCol));
			}
		}
	}

	if (0 == pdrgpul->UlLength())
	{
		// mapping failed
		pdrgpul->Release();
		pdrgpul = NULL;
	}

	return pdrgpul;
}

//---------------------------------------------------------------------------
//	@function:
//		CParseHandlerTraceFlags::StartElement
//
//	@doc:
//		Invoked by Xerces to process an opening tag
//
//---------------------------------------------------------------------------
void
CParseHandlerTraceFlags::StartElement
	(
	const XMLCh* const , //xmlszUri,
	const XMLCh* const xmlszLocalname,
	const XMLCh* const , //xmlszQname,
	const Attributes& attrs
	)
{	
	if(0 != XMLString::compareString(CDXLTokens::XmlstrToken(EdxltokenTraceFlags), xmlszLocalname))
	{
		CWStringDynamic *pstr = CDXLUtils::PstrFromXMLCh(m_pphm->Pmm(), xmlszLocalname);
		GPOS_RAISE(gpdxl::ExmaDXL, gpdxl::ExmiDXLUnexpectedTag, pstr->Wsz());
	}
	
	// parse and tokenize traceflags
	const XMLCh *xmlszTraceFlags = CDXLOperatorFactory::XmlstrFromAttrs
															(
															attrs,
															EdxltokenValue,
															EdxltokenTraceFlags
															);
	
	DrgPul *pdrgpul = CDXLOperatorFactory::PdrgpulFromXMLCh
												(
												m_pphm->Pmm(),
												xmlszTraceFlags, 
												EdxltokenDistrColumns,
												EdxltokenRelation
												);
	
	for (ULONG ul = 0; ul < pdrgpul->UlLength(); ul++)
	{
		ULONG *pul = (*pdrgpul)[ul];
		m_pbs->FExchangeSet(*pul);
	}
	
	pdrgpul->Release();
}

//---------------------------------------------------------------------------
//	@function:
//		CPartIndexMap::PdrgpulScanIds
//
//	@doc:
//		 Extract scan ids
//
//---------------------------------------------------------------------------
DrgPul *
CPartIndexMap::PdrgpulScanIds
	(
	IMemoryPool *pmp,
	BOOL fConsumersOnly
	)
	const
{
	DrgPul *pdrgpul = GPOS_NEW(pmp) DrgPul(pmp);
	PartIndexMapIter pimi(m_pim);
	while (pimi.FAdvance())
	{
		const CPartTableInfo *ppti = pimi.Pt();
		if (fConsumersOnly && EpimConsumer != ppti->Epim())
		{
			continue;
		}

		pdrgpul->Append(GPOS_NEW(pmp) ULONG(ppti->UlScanId()));
	}

	return pdrgpul;
}

//---------------------------------------------------------------------------
//	@function:
//		CPartitionPropagationSpec::AppendEnforcers
//
//	@doc:
//		Add required enforcers to dynamic array
//
//---------------------------------------------------------------------------
void
CPartitionPropagationSpec::AppendEnforcers
	(
	IMemoryPool *pmp,
	CExpressionHandle &exprhdl,
	CReqdPropPlan *
#ifdef GPOS_DEBUG
	prpp
#endif // GPOS_DEBUG
	,
	DrgPexpr *pdrgpexpr, 
	CExpression *pexpr
	)
{
	GPOS_ASSERT(NULL != prpp);
	GPOS_ASSERT(NULL != pmp);
	GPOS_ASSERT(NULL != pdrgpexpr);
	GPOS_ASSERT(NULL != pexpr);
	
	DrgPul *pdrgpul = m_ppim->PdrgpulScanIds(pmp);
	const ULONG ulSize = pdrgpul->UlLength();
	
	for (ULONG ul = 0; ul < ulSize; ul++)
	{
		ULONG ulScanId = *((*pdrgpul)[ul]);
		GPOS_ASSERT(m_ppim->FContains(ulScanId));
		
		if (CPartIndexMap::EpimConsumer != m_ppim->Epim(ulScanId) || 0 < m_ppim->UlExpectedPropagators(ulScanId))
		{
			continue;
		}
		
		if (!FRequiresPartitionPropagation(pmp, pexpr, exprhdl, ulScanId))
		{
			continue;
		}
		
		CExpression *pexprResolver = NULL;

		IMDId *pmdid = m_ppim->PmdidRel(ulScanId);
		DrgDrgPcr *pdrgpdrgpcrKeys = NULL;
		DrgPpartkeys *pdrgppartkeys = m_ppim->Pdrgppartkeys(ulScanId);
		CPartConstraint *ppartcnstr = m_ppim->PpartcnstrRel(ulScanId);
		PartCnstrMap *ppartcnstrmap = m_ppim->Ppartcnstrmap(ulScanId);
		pmdid->AddRef();
		ppartcnstr->AddRef();
		ppartcnstrmap->AddRef();
		pexpr->AddRef();
		
		// check if there is a predicate on this part index id
		HMUlExpr *phmulexprEqFilter = GPOS_NEW(pmp) HMUlExpr(pmp);
		HMUlExpr *phmulexprFilter = GPOS_NEW(pmp) HMUlExpr(pmp);
		CExpression *pexprResidual = NULL;
		if (m_ppfm->FContainsScanId(ulScanId))
		{
			CExpression *pexprScalar = PexprFilter(pmp, ulScanId);
			
			// find out which keys are used in the predicate, in case there are multiple
			// keys at this point (e.g. from a union of multiple CTE consumers)
			CColRefSet *pcrsUsed = CDrvdPropScalar::Pdpscalar(pexprScalar->PdpDerive())->PcrsUsed();
			const ULONG ulKeysets = pdrgppartkeys->UlLength();
			for (ULONG ulKey = 0; NULL == pdrgpdrgpcrKeys && ulKey < ulKeysets; ulKey++)
			{
				// get partition key
				CPartKeys *ppartkeys = (*pdrgppartkeys)[ulKey];
				if (ppartkeys->FOverlap(pcrsUsed))
				{
					pdrgpdrgpcrKeys = ppartkeys->Pdrgpdrgpcr();
				}
			}
			
                        // if we cannot find partition keys mapping the partition predicates, fall back to planner
                        if (NULL == pdrgpdrgpcrKeys)
                        {
                            GPOS_RAISE(gpopt::ExmaGPOPT, gpopt::ExmiUnsatisfiedRequiredProperties);
                        }

			pdrgpdrgpcrKeys->AddRef();

			// split predicates and put them in the appropriate hashmaps
			SplitPartPredicates(pmp, pexprScalar, pdrgpdrgpcrKeys, phmulexprEqFilter, phmulexprFilter, &pexprResidual);
			pexprScalar->Release();
		}
		else
		{
			// doesn't matter which keys we use here since there is no filter
			GPOS_ASSERT(1 <= pdrgppartkeys->UlLength());
			pdrgpdrgpcrKeys = (*pdrgppartkeys)[0]->Pdrgpdrgpcr();
			pdrgpdrgpcrKeys->AddRef();
		}

		pexprResolver = GPOS_NEW(pmp) CExpression
//.........这里部分代码省略.........

//---------------------------------------------------------------------------
//	@function:
//		CLogicalDifference::PstatsDerive
//
//	@doc:
//		Derive statistics
//
//---------------------------------------------------------------------------
IStatistics *
CLogicalDifference::PstatsDerive
(
    IMemoryPool *pmp,
    CExpressionHandle &exprhdl,
    DrgPstat * // not used
)
const
{
    GPOS_ASSERT(Esp(exprhdl) > EspNone);

    // difference is transformed into an aggregate over a LASJ,
    // we follow the same route to compute statistics
    DrgPcrs *pdrgpcrsOutput = GPOS_NEW(pmp) DrgPcrs(pmp);
    const ULONG ulSize = m_pdrgpdrgpcrInput->UlLength();
    for (ULONG ul = 0; ul < ulSize; ul++)
    {
        CColRefSet *pcrs = GPOS_NEW(pmp) CColRefSet(pmp, (*m_pdrgpdrgpcrInput)[ul]);
        pdrgpcrsOutput->Append(pcrs);
    }

    IStatistics *pstatsOuter = exprhdl.Pstats(0);
    IStatistics *pstatsInner = exprhdl.Pstats(1);

    // construct the scalar condition for the LASJ
    CExpression *pexprScCond = CUtils::PexprConjINDFCond(pmp, m_pdrgpdrgpcrInput);

    // compute the statistics for LASJ
    CColRefSet *pcrsOuterRefs = exprhdl.Pdprel()->PcrsOuter();
    DrgPstatsjoin *pdrgpstatsjoin = CStatsPredUtils::Pdrgpstatsjoin
                                    (
                                        pmp,
                                        exprhdl,
                                        pexprScCond,
                                        pdrgpcrsOutput,
                                        pcrsOuterRefs
                                    );
    IStatistics *pstatsLASJ = pstatsOuter->PstatsLASJoin
                              (
                                  pmp,
                                  pstatsInner,
                                  pdrgpstatsjoin,
                                  true /* fIgnoreLasjHistComputation */
                              );

    // clean up
    pexprScCond->Release();
    pdrgpstatsjoin->Release();

    // computed columns
    DrgPul *pdrgpulComputedCols = GPOS_NEW(pmp) DrgPul(pmp);
    IStatistics *pstats = CLogicalGbAgg::PstatsDerive
                          (
                              pmp,
                              pstatsLASJ,
                              (*m_pdrgpdrgpcrInput)[0], // we group by the columns of the first child
                              pdrgpulComputedCols, // no computed columns for set ops
                              NULL // no keys, use all grouping cols
                          );

    // clean up
    pdrgpulComputedCols->Release();
    pstatsLASJ->Release();
    pdrgpcrsOutput->Release();

    return pstats;
}