Method generateEquiJoin

src/jrd/optimizer/Optimizer.cpp:2529–2785

//

bool Optimizer::generateEquiJoin(RiverList& rivers, JoinType joinType)
{
	fb_assert(joinType != OUTER_JOIN);

	ULONG selected_rivers[OPT_STREAM_BITS], selected_rivers2[OPT_STREAM_BITS];
	ValueExprNode** eq_class;

	RiverList orgRivers(rivers);

	// Find dependent rivers and exclude them from processing

	for (River** iter = orgRivers.begin(); iter < orgRivers.end();)
	{
		const auto river = *iter;

		StreamStateHolder stateHolder2(csb, river->getStreams());
		stateHolder2.activate();

		if (river->isComputable(csb))
		{
			iter++;
			continue;
		}

		orgRivers.remove(iter);
	}

	// Count the number of "rivers" involved in the operation, then allocate
	// a scratch block large enough to hold values to compute equality
	// classes.

	const auto orgCount = (unsigned) orgRivers.getCount();

	if (orgCount < 2)
		return false;

	HalfStaticArray<ValueExprNode*, OPT_STATIC_ITEMS> scratch;
	scratch.grow(baseConjuncts * orgCount);
	ValueExprNode** classes = scratch.begin();

	// Compute equivalence classes among streams. This involves finding groups
	// of streams joined by field equalities.

	ValueExprNode** last_class = classes;

	auto iter = getBaseConjuncts();
	for (; iter.hasData(); ++iter)
	{
		if (iter & CONJUNCT_USED)
			continue;

		if (!iter->computable(csb, INVALID_STREAM, false))
			continue;

		NestConst<ValueExprNode> node1;
		NestConst<ValueExprNode> node2;

		if (!getEquiJoinKeys(*iter, &node1, &node2))