Method internalGetRecord

src/jrd/recsrc/MergeJoin.cpp:138–336

}

bool MergeJoin::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;

	// If there is a record group already formed, fetch the next combination

	if (fetchRecord(tdbb, m_args.getCount() - 1))
		return true;

	// Assuming we are done with the current value group, advance each
	// stream one record. If any comes up dry, we're done.
	const NestConst<SortedStream>* highest_ptr = m_args.begin();
	FB_SIZE_T highest_index = 0;

	for (FB_SIZE_T i = 0; i < m_args.getCount(); i++)
	{
		const NestConst<SortedStream>* const ptr = &m_args[i];
		const SortedStream* const sort_rsb = *ptr;
		const NestValueArray* const sort_key = m_keys[i];
		Impure::irsb_mrg_repeat* const tail = &impure->irsb_mrg_rpt[i];

		MergeFile* const mfb = &tail->irsb_mrg_file;

		// reset equality group record positions

		tail->irsb_mrg_equal = 0;
		tail->irsb_mrg_equal_current = 0;
		tail->irsb_mrg_equal_end = 0;

		// If there is a record waiting, use it. Otherwise get another.

		SLONG record = tail->irsb_mrg_last_fetched;
		if (record >= 0)
		{
			tail->irsb_mrg_last_fetched = -1;
			const UCHAR* const last_data = getData(tdbb, mfb, record);
			mfb->mfb_current_block = 0;

			UCHAR* const first_data = getData(tdbb, mfb, 0);
			if (first_data != last_data)
				memcpy(first_data, last_data, sort_rsb->getLength());

			mfb->mfb_equal_records = 1;
			record = 0;
		}
		else
		{
			mfb->mfb_current_block = 0;
			mfb->mfb_equal_records = 0;
			if ((record = getRecordByIndex(tdbb, i)) < 0)
				return false;
		}