greenplumn CXformExpandNAryJoinGreedy 源码
greenplumn CXformExpandNAryJoinGreedy 代码
文件路径：/src/backend/gporca/libgpopt/include/gpopt/xforms/CXformExpandNAryJoinGreedy.h
//---------------------------------------------------------------------------
// Greenplum Database
// Copyright (C) 2018 VMware, Inc. or its affiliates.
//
// @filename:
// CXformExpandNAryJoinGreedy.h
//
// @doc:
// Expand n-ary join into series of binary joins while minimizing
// cardinality of intermediate results and delay cross joins to
// the end
//---------------------------------------------------------------------------
#ifndef GPOPT_CXformExpandNAryJoinGreedy_H
#define GPOPT_CXformExpandNAryJoinGreedy_H
#include "gpos/base.h"
#include "gpopt/xforms/CXformExploration.h"
namespace gpopt
{
using namespace gpos;
//---------------------------------------------------------------------------
// @class:
// CXformExpandNAryJoinGreedy
//
// @doc:
// Expand n-ary join into series of binary joins while minimizing
// cardinality of intermediate results and delay cross joins to
// the end
//
//---------------------------------------------------------------------------
class CXformExpandNAryJoinGreedy : public CXformExploration
{
private:
public:
CXformExpandNAryJoinGreedy(const CXformExpandNAryJoinGreedy &) = delete;
// ctor
explicit CXformExpandNAryJoinGreedy(CMemoryPool *pmp);
// dtor
~CXformExpandNAryJoinGreedy() override = default;
// ident accessors
EXformId
Exfid() const override
{
return ExfExpandNAryJoinGreedy;
}
// return a string for xform name
const CHAR *
SzId() const override
{
return "CXformExpandNAryJoinGreedy";
}
// 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 CXformExpandNAryJoinGreedy
} // namespace gpopt
#endif // !GPOPT_CXformExpandNAryJoinGreedy_H
// EOF
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