Function GenerateJoinNodes

src/backend/gpopt/utils/COptTasks.cpp:508–575

--------------------------------------------------------------------------- @function: GenerateJoinNodes @doc: Converts OuterInnerRels into a JoinNode structure ---------------------------------------------------------------------------

//		Converts OuterInnerRels into a JoinNode structure
//---------------------------------------------------------------------------
CJoinHint::JoinNode *
GenerateJoinNodes(CMemoryPool *mp, OuterInnerRels *outer_inner,
				  gpos::set<std::string> &aliases)
{
	if (nullptr == outer_inner)
	{
		return nullptr;
	}

	CJoinHint::JoinNode *pair = nullptr;

	if (outer_inner->relation != nullptr)
	{
		// Base case: processing outer_inner leaf node
		char *str_buffer =
			GPOS_NEW_ARRAY(mp, char, strlen(outer_inner->relation) + 1);
		memcpy(str_buffer, outer_inner->relation,
			   strlen(outer_inner->relation));
		str_buffer[strlen(outer_inner->relation)] = '\0';

		if (aliases.count(std::string(str_buffer)) > 0)
		{
			// invalid leading hint if alias is specified more than once
			return nullptr;
		}
		aliases.insert(std::string(str_buffer));

		CWStringConst *alias = GPOS_NEW(mp)
			CWStringConst(mp, str_buffer /*outer_inner->relation*/);

		GPOS_DELETE_ARRAY(str_buffer);

		pair = GPOS_NEW(mp) CJoinHint::JoinNode(alias);
	}
	else if (2 == list_length(outer_inner->outer_inner_pair))
	{
		// Recursive case: processing outer_inner branch node
		CJoinHint::JoinNode *left_joinnode = GenerateJoinNodes(
			mp,
			(OuterInnerRels *) lfirst(list_head(outer_inner->outer_inner_pair)),
			aliases);

		CJoinHint::JoinNode *right_joinnode = GenerateJoinNodes(
			mp,
			(OuterInnerRels *) lfirst(
				list_second_cell(outer_inner->outer_inner_pair)),
			aliases);

		if (nullptr == left_joinnode || nullptr == right_joinnode)
		{
			// bad input - outer_inner may be malformed
			CRefCount::SafeRelease(left_joinnode);
			CRefCount::SafeRelease(right_joinnode);
			return nullptr;
		}

		pair = GPOS_NEW(mp) CJoinHint::JoinNode(left_joinnode, right_joinnode,
												/*is_directed*/ true);