greenplumn CXformExploration 代码
文件路径：/src/backend/gporca/libgpopt/include/gpopt/xforms/CXformExploration.h
/---------------------------------------------------------------------------
/ Greenplum Database
/ Copyright (C) 2011 EMC Corp.
/
/ @filename:
/ CXformExploration.h
/
/ @doc:
/ Base class for exploration transforms
/---------------------------------------------------------------------------
#ifndef GPOPT_CXformExploration_H
#define GPOPT_CXformExploration_H
#include "gpos/base.h"
#include "gpopt/xforms/CXform.h"
namespace gpopt
{
using namespace gpos;
/---------------------------------------------------------------------------
/ @class:
/ CXformExploration
/
/ @doc:
/ Base class for all explorations
/
/---------------------------------------------------------------------------
class CXformExploration : public CXform
{
private:
public:
CXformExploration(const CXformExploration &) = delete;
/ ctor
explicit CXformExploration(CExpression *pexpr);
/ dtor
~CXformExploration() override;
/ type of operator
BOOL
FExploration() const override
{
GPOS_ASSERT(!FSubstitution() && !FImplementation());
return true;
}
/ is transformation a subquery unnesting (Subquery To Apply) xform?
virtual BOOL
FSubqueryUnnesting() const
{
return false;
}
/ is transformation an Apply decorrelation (Apply To Join) xform?
virtual BOOL
FApplyDecorrelating() const
{
return false;
}
/ do stats need to be computed before applying xform?
virtual BOOL
FNeedsStats() const
{
return false;
}
/ conversion function
static CXformExploration *
Pxformexp(CXform *pxform)
{
GPOS_ASSERT(nullptr != pxform);
GPOS_ASSERT(pxform->FExploration());
return dynamic_cast<CXformExploration *>(pxform);
}
}; / class CXformExploration
} / namespace gpopt
#endif / !GPOPT_CXformExploration_H
/ EOF
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