Method generateOuterJoin

src/jrd/optimizer/Optimizer.cpp:2826–2978

//

RecordSource* Optimizer::generateOuterJoin(RiverList& rivers,
										   SortNode** sortClause)
{
	struct {
		RecordSource* stream_rsb;
		StreamType stream_num;
	} stream_o, stream_i, *stream_ptr[2];

	// Determine which stream should be outer and which is inner.
	// In the case of a left join, the syntactically left stream is the
	// outer, and the right stream is the inner.  For all others, swap
	// the sense of inner and outer, though for a full join it doesn't
	// matter and we should probably try both orders to see which is
	// more efficient.
	if (!rse->isLeftJoin())
	{
		stream_ptr[1] = &stream_o;
		stream_ptr[0] = &stream_i;
	}
	else
	{
		stream_ptr[0] = &stream_o;
		stream_ptr[1] = &stream_i;
	}

	// Loop through the outer join sub-streams in
	// reverse order because rivers may have been PUSHed
	for (int i = 1; i >= 0; i--)
	{
		const auto node = rse->rse_relations[i];

		if (nodeIs<RelationSourceNode>(node) || nodeIs<LocalTableSourceNode>(node))
		{
			stream_ptr[i]->stream_rsb = nullptr;
			stream_ptr[i]->stream_num = node->getStream();
		}
		else
		{
			River* const river = rivers.pop();
			stream_ptr[i]->stream_rsb = river->getRecordSource();
		}
	}

	if (!isFullJoin())
	{
		// Generate rsbs for the sub-streams.
		// For the left sub-stream we also will get a boolean back.
		BoolExprNode* boolean = nullptr;

		if (!stream_o.stream_rsb)
		{
			stream_o.stream_rsb =
				generateRetrieval(stream_o.stream_num, sortClause, true, false, &boolean);
		}
		else
		{
			// Ensure the inner streams are inactive
			StreamList streams;