Method findDependentStreams

src/jrd/optimizer/Optimizer.cpp:2346–2404

//

void Optimizer::findDependentStreams(const RiverList& rivers,
									 const StreamList& streams,
									 StreamList& dependentStreams,
									 StreamList& freeStreams)
{
#ifdef OPT_DEBUG_RETRIEVAL
	if (streams.hasData())
		printf("Detecting dependent streams:\n");
#endif

	for (const auto stream : streams)
	{
		const auto tail = &csb->csb_rpt[stream];

		// Set temporary active flag for this stream
		tail->activate();

		bool dependent = false;

		if (conjuncts.hasData())
		{
			// Calculate the inversion for this stream.
			// The returning candidate contains the streams that will be used for
			// index retrieval. This meant that if some stream is used this stream
			// depends on already active streams and can not be used in a separate
			// SORT/MERGE.

			Retrieval retrieval(tdbb, this, stream, false, false, nullptr, true);
			const auto candidate = retrieval.getInversion();

			if (candidate->dependentFromStreams.hasData())
			{
				dependent = true;

				StreamList checkStreams;
				checkStreams.add(stream);

				for (const auto river : rivers)
				{
					// If some river already depends on this stream,
					// then itself it cannot be dependent
					if (river->isDependent(checkStreams))
					{
						dependent = false;
						break;
					}
				}
			}
		}

		if (dependent)
			dependentStreams.add(stream);
		else
			freeStreams.add(stream);

		// Reset active flag
		tail->deactivate();
	}