greenplumn CXformJoinAssociativity 代码
文件路径：/src/backend/gporca/libgpopt/src/xforms/CXformJoinAssociativity.cpp
/---------------------------------------------------------------------------
/ Greenplum Database
/ Copyright (C) 2011 EMC Corp.
/
/ @filename:
/ CXformJoinAssociativity.cpp
/
/ @doc:
/ Implementation of associativity transform for left-deep joins
/---------------------------------------------------------------------------
#include "gpopt/xforms/CXformJoinAssociativity.h"
#include "gpos/base.h"
#include "gpopt/metadata/CTableDescriptor.h"
#include "gpopt/operators/CLogicalInnerJoin.h"
#include "gpopt/operators/CPatternLeaf.h"
#include "gpopt/operators/CPatternTree.h"
#include "gpopt/operators/CPredicateUtils.h"
using namespace gpopt;
using namespace gpmd;
using namespace gpnaucrates;
#define GPOPT_MAX_JOIN_DEPTH_FOR_ASSOCIATIVITY 20
#define GPOPT_MAX_JOIN_RIGHT_CHILD_DEPTH_FOR_ASSOCIATIVITY 1
/---------------------------------------------------------------------------
/ @function:
/ CXformJoinAssociativity::CXformJoinAssociativity
/
/ @doc:
/ Ctor
/
/---------------------------------------------------------------------------
CXformJoinAssociativity::CXformJoinAssociativity(CMemoryPool *mp)
: CXformExploration(
/ pattern
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CLogicalInnerJoin(mp),
GPOS_NEW(mp) CExpression / left child is a join tree
(mp, GPOS_NEW(mp) CLogicalInnerJoin(mp),
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPatternLeaf(mp)), / left child
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPatternLeaf(mp)), / right child
GPOS_NEW(mp)
CExpression(mp, GPOS_NEW(mp) CPatternTree(mp)) / predicate
),
GPOS_NEW(mp) CExpression / right child is a pattern leaf
(mp, GPOS_NEW(mp) CPatternLeaf(mp)),
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPatternTree(mp)) / join predicate
))
{
}
/---------------------------------------------------------------------------
/ @function:
/ CXformJoinAssociativity::CreatePredicates
/
/ @doc:
/ Extract all conjuncts and divvy them up between upper and lower join
/
/---------------------------------------------------------------------------
void
CXformJoinAssociativity::CreatePredicates(CMemoryPool *mp, CExpression *pexpr,
CExpressionArray *pdrgpexprLower,
CExpressionArray *pdrgpexprUpper)
{
GPOS_CHECK_ABORT;
/ bind operators
CExpression *pexprLeft = (*pexpr)[0];
CExpression *pexprLeftLeft = (*pexprLeft)[0];
CExpression *pexprRight = (*pexpr)[1];
CExpressionArray *pdrgpexprJoins = GPOS_NEW(mp) CExpressionArray(mp);
pexprLeft->AddRef();
pdrgpexprJoins->Append(pexprLeft);
pexpr->AddRef();
pdrgpexprJoins->Append(pexpr);
/ columns for new lower join
CColRefSet *pcrsLower = GPOS_NEW(mp) CColRefSet(mp);
pcrsLower->Union(pexprLeftLeft->DeriveOutputColumns());
pcrsLower->Union(pexprRight->DeriveOutputColumns());
/ convert current predicates into arrays of conjuncts
CExpressionArray *pdrgpexprOrig = GPOS_NEW(mp) CExpressionArray(mp);
for (ULONG ul = 0; ul < 2; ul++)
{
CExpressionArray *pdrgpexprPreds = CPredicateUtils::PdrgpexprConjuncts(
mp, (*(*pdrgpexprJoins)[ul])[2]);
ULONG length = pdrgpexprPreds->Size();
for (ULONG ulConj = 0; ulConj < length; ulConj++)
{
CExpression *pexprConj = (*pdrgpexprPreds)[ulConj];
pexprConj->AddRef();
pdrgpexprOrig->Append(pexprConj);
}
pdrgpexprPreds->Release();
}
/ divvy up conjuncts for upper and lower join
ULONG ulConj = pdrgpexprOrig->Size();
for (ULONG ul = 0; ul < ulConj; ul++)
{
CExpression *pexprPred = (*pdrgpexprOrig)[ul];
CColRefSet *pcrs = pexprPred->DeriveUsedColumns();
pexprPred->AddRef();
if (pcrsLower->ContainsAll(pcrs))
{
pdrgpexprLower->Append(pexprPred);
}
else
{
pdrgpexprUpper->Append(pexprPred);
}
}
/ No predicates indicate a cross join. And for that, ORCA expects
/ predicate to be a scalar const "true".
if (pdrgpexprLower->Size() == 0)
{
CExpression *pexprCrossLowerJoinPred =
CUtils::PexprScalarConstBool(mp, true, false);
pdrgpexprLower->Append(pexprCrossLowerJoinPred);
}
/ Same for upper predicates
if (pdrgpexprUpper->Size() == 0)
{
CExpression *pexprCrossUpperJoinPred =
CUtils::PexprScalarConstBool(mp, true, false);
pdrgpexprUpper->Append(pexprCrossUpperJoinPred);
}
/ clean up
pcrsLower->Release();
pdrgpexprOrig->Release();
pdrgpexprJoins->Release();
}
/---------------------------------------------------------------------------
/ @function:
/ CXformJoinAssociativity::Exfp
/
/ @doc:
/ Compute xform promise for a given expression handle
/
/---------------------------------------------------------------------------
CXform::EXformPromise
CXformJoinAssociativity::Exfp(CExpressionHandle &exprhdl) const
{
if (GPOPT_MAX_JOIN_DEPTH_FOR_ASSOCIATIVITY <
exprhdl
.DeriveJoinDepth() || / disallow xform beyond max join depth
GPOPT_MAX_JOIN_RIGHT_CHILD_DEPTH_FOR_ASSOCIATIVITY <
exprhdl.DeriveJoinDepth(
1) / disallow xform if input is not a left deep tree
)
{
/ restrict associativity to left-deep trees by prohibiting the
/ transformation when right child's join depth is above threshold
return CXform::ExfpNone;
}
return CXform::ExfpHigh;
}
/ Associativity Transform: (RS)T ==> (RT)S
/ Example:
/ Input Expression:
/ +--CLogicalInnerJoin
/ |--CLogicalInnerJoin
/ | |--CLogicalGet "t1"
/ | |--CLogicalGet "t2"
/ | +--CScalarCmp (=)
/ | |--CScalarIdent "a" (0) ==> from t1
/ | +--CScalarIdent "b" (9) ==> from t2
/ |--CLogicalGet "t3"
/ +--CScalarCmp (=)
/ |--CScalarIdent "a" (0) ==> from t1
/ +--CScalarIdent "c" (19) ==> from t3
/
/ Output CExpression:
/ +--CLogicalInnerJoin
/ |--CLogicalInnerJoin
/ | |--CLogicalGet "t1"
/ | |--CLogicalGet "t3"
/ | +--CScalarCmp (=)
/ | |--CScalarIdent "a" (0) ==> from t1
/ | +--CScalarIdent "c" (19) ==> from t3
/ |--CLogicalGet "t2"
/ +--CScalarCmp (=)
/ |--CScalarIdent "a" (0) ==> from t1
/ +--CScalarIdent "b" (9) ==> from t2
void
CXformJoinAssociativity::Transform(CXformContext *pxfctxt, CXformResult *pxfres,
CExpression *pexpr) const
{
GPOS_ASSERT(nullptr != pxfctxt);
GPOS_ASSERT(FPromising(pxfctxt->Pmp(), this, pexpr));
GPOS_ASSERT(FCheckPattern(pexpr));
CMemoryPool *mp = pxfctxt->Pmp();
/ create new predicates
CExpressionArray *pdrgpexprLower = GPOS_NEW(mp) CExpressionArray(mp);
CExpressionArray *pdrgpexprUpper = GPOS_NEW(mp) CExpressionArray(mp);
CreatePredicates(mp, pexpr, pdrgpexprLower, pdrgpexprUpper);
GPOS_ASSERT(pdrgpexprLower->Size() > 0);
/ cross join contains CScalarConst(1) as the join condition. if the
/ input expression is as below with cross join at top level between
/ CLogicalInnerJoin and CLogicalGet "t3"
/ +--CLogicalInnerJoin
/ |--CLogicalInnerJoin
/ | |--CLogicalGet "t1"
/ | |--CLogicalGet "t2"
/ | +--CScalarCmp (=)
/ | |--CScalarIdent "a" (0)
/ | +--CScalarIdent "b" (9)
/ |--CLogicalGet "t3"
/ +--CScalarConst (1)
/ for the above expression (lower) predicate generated for the cross join
/ between t1 and t3 will be: CScalarConst (1) In *only* such cases, donot
/ generate such alternative with the lower join as cross join example:
/ +--CLogicalInnerJoin
/ |--CLogicalInnerJoin
/ | |--CLogicalGet "t1"
/ | |--CLogicalGet "t3"
/ | +--CScalarConst (1)
/ |--CLogicalGet "t2"
/ +--CScalarCmp (=)
/ |--CScalarIdent "a" (0)
/ +--CScalarIdent "b" (9)
/ NOTE that we want to be careful to check that input lower join wasn't a
/ cross join to begin with, because we want to build a join in this case even
/ though a new cross join will be created.
/ check if the input lower join expression is a cross join
BOOL fInputLeftIsCrossJoin = CUtils::FCrossJoin((*pexpr)[0]);
/ check if the output lower join would result in a cross join
BOOL fOutputLeftIsCrossJoin =
(1 == pdrgpexprLower->Size() &&
CUtils::FScalarConstTrue((*pdrgpexprLower)[0]));
/ build a join only if it does not result in a cross join
/ unless the input itself was a cross join (see earlier comments)
if (!fOutputLeftIsCrossJoin || fInputLeftIsCrossJoin)
{
/ bind operators
CExpression *pexprLeft = (*pexpr)[0];
CExpression *pexprLeftLeft = (*pexprLeft)[0];
CExpression *pexprLeftRight = (*pexprLeft)[1];
CExpression *pexprRight = (*pexpr)[1];
/ add-ref all components for re-use
pexprLeftLeft->AddRef();
pexprRight->AddRef();
pexprLeftRight->AddRef();
/ build new joins
CExpression *pexprBottomJoin =
CUtils::PexprLogicalJoin<CLogicalInnerJoin>(
mp, pexprLeftLeft, pexprRight,
CPredicateUtils::PexprConjunction(mp, pdrgpexprLower));
CExpression *pexprResult = CUtils::PexprLogicalJoin<CLogicalInnerJoin>(
mp, pexprBottomJoin, pexprLeftRight,
CPredicateUtils::PexprConjunction(mp, pdrgpexprUpper));
/ add alternative to transformation result
pxfres->Add(pexprResult);
}
else
{
pdrgpexprLower->Release();
pdrgpexprUpper->Release();
}
}
/ EOF
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