Method formRiver

src/jrd/optimizer/InnerJoin.cpp:498–623

//

River* InnerJoin::formRiver()
{
	fb_assert(bestCount);
	fb_assert(bestStreams.getCount() == bestCount);

	const auto orgSortPtr = sortPtr;
	const auto orgSortNode = sortPtr ? *sortPtr : nullptr;

	if (bestCount != innerStreams.getCount())
		sortPtr = nullptr;

	RecordSource* rsb;
	StreamList streams;
	HalfStaticArray<RecordSource*, OPT_STATIC_ITEMS> rsbs;
	HalfStaticArray<BoolExprNode*, OPT_STATIC_ITEMS> equiMatches;

	for (const auto& stream : bestStreams)
	{
		const bool sortUtilized = (orgSortNode && !*orgSortPtr);

		// We use hash join instead of nested loop join if:
		//  - stream has equivalence relationship(s) with the prior streams
		//    (and hashing was estimated to be cheaper)
		//  AND
		//    - optimization for first rows is not requested
		//    OR
		//    - existing sort was not utilized using an index

		if (rsbs.hasData() && // this is not the first stream
			stream.equiMatches.hasData() &&
			(!optimizer->favorFirstRows() || !sortUtilized))
		{
			fb_assert(streams.hasData());

			// Deactivate priorly joined streams
			StreamStateHolder stateHolder(csb, streams);
			stateHolder.deactivate();

			// Create an independent retrieval
			rsb = optimizer->generateRetrieval(stream.number, sortPtr, false, false);

			// Create a nested loop join from the priorly processed streams
			const auto priorRsb = (rsbs.getCount() == 1) ? rsbs[0] :
				FB_NEW_POOL(getPool()) NestedLoopJoin(csb, rsbs.getCount(), rsbs.begin());

			// Prepare record sources and corresponding equivalence keys for hash-joining
			RecordSource* hashJoinRsbs[] = {priorRsb, rsb};

			HalfStaticArray<NestValueArray*, OPT_STATIC_ITEMS> keys;

			keys.add(FB_NEW_POOL(getPool()) NestValueArray(getPool()));
			keys.add(FB_NEW_POOL(getPool()) NestValueArray(getPool()));

			for (const auto match : stream.equiMatches)
			{
				NestConst<ValueExprNode> node1;
				NestConst<ValueExprNode> node2;