C++ (Cpp) CExpression::Pgexprの例

コード例 #1

ファイル: CBinding.cpp プロジェクト: HanumathRao/gporca

//---------------------------------------------------------------------------
//	@function:
//		CBinding::FAdvanceChildCursors
//
//	@doc:
//		Advance cursors of child expressions and populate the given array
//		with the next child expressions
//
//---------------------------------------------------------------------------
BOOL
CBinding::FAdvanceChildCursors
	(
	IMemoryPool *pmp,
	CGroupExpression *pgexpr,
	CExpression *pexprPattern,
	CExpression *pexprLast,
	DrgPexpr *pdrgpexpr
	)
{
	GPOS_ASSERT(NULL != pexprPattern);
	GPOS_ASSERT(NULL != pdrgpexpr);

	const ULONG ulArity = pgexpr->UlArity();
	if (NULL == pexprLast)
	{
		// first call, initialize cursors
		return FInitChildCursors(pmp, pgexpr, pexprPattern, pdrgpexpr);
	}

	// could we advance a child's cursor?
	BOOL fCursorAdvanced = false;

	// number of exhausted cursors
	ULONG ulExhaustedCursors = 0;

	for (ULONG ul = 0; ul < ulArity; ul++)
	{
		CGroup *pgroup = (*pgexpr)[ul];
		CExpression *pexprPatternChild = PexprExpandPattern(pexprPattern, ul, ulArity);
		CExpression *pexprNewChild = NULL;

		if (fCursorAdvanced)
		{
			// re-use last extracted child expression
			(*pexprLast)[ul]->AddRef();
			pexprNewChild = (*pexprLast)[ul];
		}
		else
		{
			CExpression *pexprLastChild = (*pexprLast)[ul];
			GPOS_ASSERT(pgroup == pexprLastChild->Pgexpr()->Pgroup());

			// advance current cursor
			pexprNewChild = PexprExtract(pmp, pgroup, pexprPatternChild, pexprLastChild);

			if (NULL == pexprNewChild)
			{
				// cursor is exhausted, we need to reset it
				pexprNewChild = PexprExtract(pmp, pgroup, pexprPatternChild, NULL /*pexprLastChild*/);
				ulExhaustedCursors++;
			}
			else
			{
				// advancing current cursor has succeeded
				fCursorAdvanced =  true;
			}
		}
		GPOS_ASSERT(NULL != pexprNewChild);

		pdrgpexpr->Append(pexprNewChild);
	}

	GPOS_ASSERT(ulExhaustedCursors <= ulArity);


	return ulExhaustedCursors < ulArity;
}