Method joinDependentStreams

src/jrd/optimizer/Optimizer.cpp:2410–2457

//

bool Optimizer::joinDependentStreams(StreamList& joinStreams, RiverList& rivers, SortNode** sort)
{
	bool hasDependentStreams = false;

	while (true)
	{
		// AB: Determine which streams have an index relationship
		// with the currently active rivers. This is needed so that
		// no merge is made between a new cross river and the
		// currently active rivers. Where in the new cross river
		// a stream depends (index) on the active rivers.
		StreamList dependentStreams, freeStreams;
		findDependentStreams(rivers, joinStreams, dependentStreams, freeStreams);

		// If we have dependent and free streams then we can't rely on
		// the sort node to be used for index navigation
		if (dependentStreams.hasData() && freeStreams.hasData())
			sort = nullptr;

		if (dependentStreams.hasData())
		{
			hasDependentStreams = true;

			// Copy free streams
			joinStreams.assign(freeStreams);

			// Make rivers from the dependent streams
			generateInnerJoin(dependentStreams, rivers, sort, rse->rse_plan);

			for (const auto depStream : dependentStreams)
				csb->csb_rpt[depStream].activate();
		}
		else
		{
			if (freeStreams.hasData())
			{
				// Deactivate streams from rivers on stack, because
				// the remaining streams don't have any indexed relationship with them
				for (const auto river : rivers)
					river->deactivate(csb);
			}

			break;
		}
	}

	return hasDependentStreams;
};


//