Method internalGetRecord

src/jrd/recsrc/HashJoin.cpp:406–539

}

bool HashJoin::internalGetRecord(thread_db* tdbb) const
{
	JRD_reschedule(tdbb);

	Request* const request = tdbb->getRequest();
	Impure* const impure = request->getImpure<Impure>(m_impure);

	if (!(impure->irsb_flags & irsb_open))
		return false;

	const auto inner = m_args.front().source;

	while (true)
	{
		if (impure->irsb_flags & irsb_mustread)
		{
			// Fetch the record from the leading stream

			if (!m_leader.source->getRecord(tdbb))
				return false;

			if (m_boolean && !m_boolean->execute(tdbb, request))
			{
				// The boolean pertaining to the left sub-stream is false
				// so just join sub-stream to a null valued right sub-stream
				inner->nullRecords(tdbb);
				return true;
			}

			// We have something to join with, so ensure the hash table is initialized

			if (!impure->irsb_hash_table && !impure->irsb_leader_buffer)
			{
				auto& pool = *tdbb->getDefaultPool();
				const auto argCount = m_args.getCount();

				impure->irsb_hash_table = FB_NEW_POOL(pool) HashTable(pool, argCount);
				impure->irsb_leader_buffer = FB_NEW_POOL(pool) UCHAR[m_leader.totalKeyLength];

				UCharBuffer buffer(pool);

				for (FB_SIZE_T i = 0; i < argCount; i++)
				{
					// Read and cache the inner streams. While doing that,
					// hash the join condition values and populate hash tables.

					m_args[i].buffer->open(tdbb);

					ULONG counter = 0;
					const auto keyBuffer = buffer.getBuffer(m_args[i].totalKeyLength, false);

					while (m_args[i].buffer->getRecord(tdbb))
					{
						const auto hash = computeHash(tdbb, request, m_args[i], keyBuffer);
						impure->irsb_hash_table->put(i, hash, counter++);
					}
				}