Method processPossibleJoins

src/jrd/RecordSourceNodes.cpp:3303–3387

}

RseNode* RseNode::processPossibleJoins(thread_db* tdbb, CompilerScratch* csb)
{
	if (!isInnerJoin() || !rse_boolean || rse_plan)
		return nullptr;

	const auto dbb = tdbb->getDatabase();
	if (!dbb->dbb_config->getSubQueryConversion())
		return nullptr;

	// If the sub-query is nested inside the other sub-query which wasn't converted into semi-join,
	// it makes no sense to apply a semi-join at the deeper levels, as a sub-query is expected
	// to be executed repeatedly.
	// This is a temporary fix until nested loop semi-joins are allowed by the optimizer.

	if (flags & FLAG_SUB_QUERY)
		return nullptr;

	for (const auto node : csb->csb_current_nodes)
	{
		if (const auto rse = nodeAs<RseNode>(node))
		{
			if (rse->flags & FLAG_SUB_QUERY)
				return nullptr;
		}
	}

	RecordSourceNodeStack rseStack;
	BoolExprNodeStack booleanStack;

	// Find possibly joinable sub-queries

	StreamList rseStreams;
	computeRseStreams(rseStreams);

	if (!findPossibleJoins(csb, rseStreams, rse_boolean.getAddress(), rseStack, booleanStack))
		return nullptr;

	fb_assert(rseStack.hasData() && booleanStack.hasData());
	fb_assert(rseStack.getCount() == booleanStack.getCount());

	// Create joins between the original node and detected joinable nodes.
	// Preserve FIRST/SKIP nodes at their original position, i.e. outside semi-joins.

	const auto first = rse_first;
	rse_first = nullptr;

	const auto skip = rse_skip;
	rse_skip = nullptr;

	const auto orgFlags = flags;
	flags = 0;

	auto rse = this;
	while (rseStack.hasData())
	{
		const auto newRse = FB_NEW_POOL(*tdbb->getDefaultPool())
			RseNode(*tdbb->getDefaultPool());