greenplumn CXformExpandNAryJoinMinCard 源码
greenplumn CXformExpandNAryJoinMinCard 代码
文件路径：/src/backend/gporca/libgpopt/include/gpopt/xforms/CXformExpandNAryJoinMinCard.h
//---------------------------------------------------------------------------
// Greenplum Database
// Copyright (C) 2012 EMC Corp.
//
// @filename:
// CXformExpandNAryJoinMinCard.h
//
// @doc:
// Expand n-ary join into series of binary joins while minimizing
// cardinality of intermediate results
//---------------------------------------------------------------------------
#ifndef GPOPT_CXformExpandNAryJoinMinCard_H
#define GPOPT_CXformExpandNAryJoinMinCard_H
#include "gpos/base.h"
#include "gpopt/xforms/CXformExploration.h"
namespace gpopt
{
using namespace gpos;
//---------------------------------------------------------------------------
// @class:
// CXformExpandNAryJoinMinCard
//
// @doc:
// Expand n-ary join into series of binary joins while minimizing
// cardinality of intermediate results
//
//---------------------------------------------------------------------------
class CXformExpandNAryJoinMinCard : public CXformExploration
{
private:
public:
CXformExpandNAryJoinMinCard(const CXformExpandNAryJoinMinCard &) = delete;
// ctor
explicit CXformExpandNAryJoinMinCard(CMemoryPool *mp);
// dtor
~CXformExpandNAryJoinMinCard() override = default;
// ident accessors
EXformId
Exfid() const override
{
return ExfExpandNAryJoinMinCard;
}
// return a string for xform name
const CHAR *
SzId() const override
{
return "CXformExpandNAryJoinMinCard";
}
// compute xform promise for a given expression handle
EXformPromise Exfp(CExpressionHandle &exprhdl) const override;
// do stats need to be computed before applying xform?
BOOL
FNeedsStats() const override
{
return true;
}
// actual transform
void Transform(CXformContext *pxfctxt, CXformResult *pxfres,
CExpression *pexpr) const override;
BOOL
IsApplyOnce() override
{
return true;
}
}; // class CXformExpandNAryJoinMinCard
} // namespace gpopt
#endif // !GPOPT_CXformExpandNAryJoinMinCard_H
// EOF
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