greenplumn CXformSimplifySubquery 源码
greenplumn CXformSimplifySubquery 代码
文件路径：/src/backend/gporca/libgpopt/include/gpopt/xforms/CXformSimplifySubquery.h
//---------------------------------------------------------------------------
// Greenplum Database
// Copyright (C) 2012 EMC Corp.
//
// @filename:
// CXformSimplifySubquery.h
//
// @doc:
// Simplify existential/quantified subqueries by transforming
// into count(*) subqueries
//---------------------------------------------------------------------------
#ifndef GPOPT_CXformSimplifySubquery_H
#define GPOPT_CXformSimplifySubquery_H
#include "gpos/base.h"
#include "gpopt/xforms/CXformExploration.h"
namespace gpopt
{
using namespace gpos;
//---------------------------------------------------------------------------
// @class:
// CXformSimplifySubquery
//
// @doc:
// Simplify existential/quantified subqueries by transforming
// into count(*) subqueries
//
//---------------------------------------------------------------------------
class CXformSimplifySubquery : public CXformExploration
{
private:
// definition of simplification function
using FnSimplify = BOOL(CMemoryPool *, CExpression *, CExpression **);
// definition of matching function
using FnMatch = BOOL(COperator *);
// transform existential subqueries to count(*) subqueries
static BOOL FSimplifyExistential(CMemoryPool *mp, CExpression *pexprScalar,
CExpression **ppexprNewScalar);
// transform quantified subqueries to count(*) subqueries
static BOOL FSimplifyQuantified(CMemoryPool *mp, CExpression *pexprScalar,
CExpression **ppexprNewScalar);
// main driver, transform existential/quantified subqueries to count(*) subqueries
static BOOL FSimplifySubqueryRecursive(CMemoryPool *mp,
CExpression *pexprScalar,
CExpression **ppexprNewScalar,
FnSimplify *pfnsimplify,
FnMatch *pfnmatch);
static CExpression *FSimplifySubquery(CMemoryPool *mp,
CExpression *pexprInput,
FnSimplify *pfnsimplify,
FnMatch *pfnmatch);
public:
CXformSimplifySubquery(const CXformSimplifySubquery &) = delete;
// ctor
explicit CXformSimplifySubquery(CExpression *pexprPattern);
// dtor
~CXformSimplifySubquery() 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;
}; // class CXformSimplifySubquery
} // namespace gpopt
#endif // !GPOPT_CXformSimplifySubquery_H
// EOF
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