greenplumn CXformSubqueryUnnest 源码
greenplumn CXformSubqueryUnnest 代码
文件路径：/src/backend/gporca/libgpopt/include/gpopt/xforms/CXformSubqueryUnnest.h
//---------------------------------------------------------------------------
// Greenplum Database
// Copyright (C) 2012 EMC Corp.
//
// @filename:
// CXformSubqueryUnnest.h
//
// @doc:
// Base class for subquery unnesting xforms
//---------------------------------------------------------------------------
#ifndef GPOPT_CXformSubqueryUnnest_H
#define GPOPT_CXformSubqueryUnnest_H
#include "gpos/base.h"
#include "gpopt/xforms/CXformExploration.h"
namespace gpopt
{
using namespace gpos;
//---------------------------------------------------------------------------
// @class:
// CXformSubqueryUnnest
//
// @doc:
// Base class for subquery unnesting xforms
//
//---------------------------------------------------------------------------
class CXformSubqueryUnnest : public CXformExploration
{
private:
protected:
// helper for subquery unnesting
static CExpression *PexprSubqueryUnnest(CMemoryPool *mp, CExpression *pexpr,
BOOL fEnforceCorrelatedApply);
// actual transform
virtual void Transform(CXformContext *pxfctxt, CXformResult *pxfres,
CExpression *pexpr,
BOOL fEnforceCorrelatedApply) const;
public:
CXformSubqueryUnnest(const CXformSubqueryUnnest &) = delete;
// ctor
explicit CXformSubqueryUnnest(CExpression *pexprPattern)
: CXformExploration(pexprPattern)
{
}
// dtor
~CXformSubqueryUnnest() override = default;
// compute xform promise for a given expression handle
EXformPromise Exfp(CExpressionHandle &exprhdl) const override;
// actual transform
void Transform(CXformContext *pxfctxt, CXformResult *pxfres,
CExpression *pexpr) const override;
// is transformation a subquery unnesting (Subquery To Apply) xform?
BOOL
FSubqueryUnnesting() const override
{
return true;
}
}; // class CXformSubqueryUnnest
} // namespace gpopt
#endif // !GPOPT_CXformSubqueryUnnest_H
// EOF
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