Function delete_node

src/jrd/btr.cpp:3385–3675

static contents delete_node(thread_db* tdbb, WIN* window, UCHAR* pointer)
{
/**************************************
 *
 *	d e l e t e _ n o d e
 *
 **************************************
 *
 * Functional description
 *	Delete a node from a page and return whether it
 *	empty, if there is a single node on it, or if it
 * 	is above or below the threshold for garbage collection.
 *
 **************************************/

	SET_TDBB(tdbb);
	const Database* dbb = tdbb->getDatabase();
	CHECK_DBB(dbb);

	btree_page* page = (btree_page*) window->win_buffer;

	CCH_MARK(tdbb, window);

	const bool leafPage = (page->btr_level == 0);

	// Read node that need to be removed
	IndexNode removingNode;
	UCHAR* localPointer = removingNode.readNode(pointer, leafPage);
	const USHORT offsetDeletePoint = (pointer - (UCHAR*) page);

	// Read the next node after the removing node
	IndexNode nextNode;
	const USHORT offsetNextPoint = (localPointer - (UCHAR*) page);
	localPointer = nextNode.readNode(localPointer, leafPage);

	// Save data in tempKey so we can rebuild from it
	USHORT newNextPrefix = nextNode.prefix;
	USHORT newNextLength = 0;
	USHORT length = MAX(removingNode.length + removingNode.prefix, nextNode.length + nextNode.prefix);
	HalfStaticArray<UCHAR, MAX_KEY> tempBuf;
	UCHAR* tempData = tempBuf.getBuffer(length);
	length = 0;
	if (nextNode.prefix > removingNode.prefix)
	{
		// The next node uses data from the node that is going to
		// be removed so save it.
		length = nextNode.prefix - removingNode.prefix;
		newNextPrefix -= length;
		newNextLength += length;
		memcpy(tempData, removingNode.data, length);
	}
	memcpy(tempData + length, nextNode.data, nextNode.length);
	newNextLength += nextNode.length;

	// Update the page prefix total.
	page->btr_prefix_total -= (removingNode.prefix + (nextNode.prefix - newNextPrefix));

	// Update the next node so we are ready to save it.