Method openStream

src/jrd/recsrc/IndexTableScan.cpp:622–675

}

UCHAR* IndexTableScan::openStream(thread_db* tdbb, Impure* impure, win* window) const
{
	temporary_key* lower = impure->irsb_nav_current_lower;
	temporary_key* upper = impure->irsb_nav_current_upper;

	setPage(tdbb, impure, NULL);
	impure->irsb_nav_length = 0;

	// Find the starting leaf page
	const IndexRetrieval* const retrieval = m_index->retrieval;
	index_desc* const idx = (index_desc*) ((SCHAR*) impure + m_offset);

	Ods::btree_page* page = BTR_find_page(tdbb, retrieval, window, idx, lower, upper);
	setPage(tdbb, impure, window);

	// find the upper limit for the search
	temporary_key* limit_ptr = NULL;
	if (retrieval->irb_upper_count)
	{
		// If upper key length is greater than declared key length, we need
		// one "excess" byte for correct comparison. Without it there could
		// be false equality hits.
		impure->irsb_nav_upper_length = MIN(m_length + 1, upper->key_length);
		memcpy(impure->irsb_nav_data + m_length, upper->key_data, impure->irsb_nav_upper_length);
	}

	if (retrieval->irb_lower_count)
		limit_ptr = lower;

	// If there is a starting descriptor, search down index to starting position.
	// This may involve sibling buckets if splits are in progress.  If there
	// isn't a starting descriptor, walk down the left side of the index.

	if (limit_ptr)
	{
		UCHAR* pointer = NULL;
		// If END_BUCKET is reached BTR_find_leaf will return NULL
		while (!(pointer = BTR_find_leaf(page, limit_ptr, impure->irsb_nav_data, NULL,
							(idx->idx_flags & idx_descending),
							(retrieval->irb_generic & (irb_starting | irb_partial)))))
		{
			page = (Ods::btree_page*) CCH_HANDOFF(tdbb, window, page->btr_sibling,
				  LCK_read, pag_index);
		}

		IndexNode node;
		node.readNode(pointer, true);

		impure->irsb_nav_length = node.prefix + node.length;
		return pointer;
	}

	return page->btr_nodes + page->btr_jump_size;
}

void IndexTableScan::setPage(thread_db* tdbb, Impure* impure, win* window) const
{