C++ GinBtree::getLeftMostPage方法代码示例

/*
 * Find correct PostingItem in non-leaf page. It supposed that page
 * correctly chosen and searching value SHOULD be on page
 */
static BlockNumber
dataLocateItem(GinBtree btree, GinBtreeStack *stack)
{
    OffsetNumber low,
                 high,
                 maxoff;
    PostingItem *pitem = NULL;
    int			result;
    Page		page = BufferGetPage(stack->buffer);

    Assert(!GinPageIsLeaf(page));
    Assert(GinPageIsData(page));

    if (btree->fullScan)
    {
        stack->off = FirstOffsetNumber;
        stack->predictNumber *= GinPageGetOpaque(page)->maxoff;
        return btree->getLeftMostPage(btree, page);
    }

    low = FirstOffsetNumber;
    maxoff = high = GinPageGetOpaque(page)->maxoff;
    Assert(high >= low);

    high++;

    while (high > low)
    {
        OffsetNumber mid = low + ((high - low) / 2);

        pitem = (PostingItem *) GinDataPageGetItem(page, mid);

        if (mid == maxoff)
        {
            /*
             * Right infinity, page already correctly chosen with a help of
             * dataIsMoveRight
             */
            result = -1;
        }
        else
        {
            pitem = (PostingItem *) GinDataPageGetItem(page, mid);
            result = ginCompareItemPointers(btree->items + btree->curitem, &(pitem->key));
        }

        if (result == 0)
        {
            stack->off = mid;
            return PostingItemGetBlockNumber(pitem);
        }
        else if (result > 0)
            low = mid + 1;
        else
            high = mid;
    }

    Assert(high >= FirstOffsetNumber && high <= maxoff);

    stack->off = high;
    pitem = (PostingItem *) GinDataPageGetItem(page, high);
    return PostingItemGetBlockNumber(pitem);
}

/*
 * Try to find parent for current stack position, returns correct
 * parent and child's offset in  stack->parent.
 * Function should never release root page to prevent conflicts
 * with vacuum process
 */
void
ginFindParents(GinBtree btree, GinBtreeStack *stack,
			   BlockNumber rootBlkno)
{

	Page		page;
	Buffer		buffer;
	BlockNumber blkno,
				leftmostBlkno;
	OffsetNumber offset;
	GinBtreeStack *root = stack->parent;
	GinBtreeStack *ptr;

	if (!root)
	{
		/* XLog mode... */
		root = (GinBtreeStack *) palloc(sizeof(GinBtreeStack));
		root->blkno = rootBlkno;
		root->buffer = ReadBuffer(btree->index, rootBlkno);
		LockBuffer(root->buffer, GIN_EXCLUSIVE);
		root->parent = NULL;
	}
	else
	{
		/*
		 * find root, we should not release root page until update is
		 * finished!!
		 */
		while (root->parent)
		{
			ReleaseBuffer(root->buffer);
			root = root->parent;
		}

		Assert(root->blkno == rootBlkno);
		Assert(BufferGetBlockNumber(root->buffer) == rootBlkno);
		LockBuffer(root->buffer, GIN_EXCLUSIVE);
	}
	root->off = InvalidOffsetNumber;

	page = BufferGetPage(root->buffer);
	Assert(!GinPageIsLeaf(page));

	/* check trivial case */
	if ((root->off = btree->findChildPtr(btree, page, stack->blkno, InvalidOffsetNumber)) != InvalidOffsetNumber)
	{
		stack->parent = root;
		return;
	}

	leftmostBlkno = blkno = btree->getLeftMostPage(btree, page);
	LockBuffer(root->buffer, GIN_UNLOCK);
	Assert(blkno != InvalidBlockNumber);

	for (;;)
	{
		buffer = ReadBuffer(btree->index, blkno);
		LockBuffer(buffer, GIN_EXCLUSIVE);
		page = BufferGetPage(buffer);
		if (GinPageIsLeaf(page))
			elog(ERROR, "Lost path");

		leftmostBlkno = btree->getLeftMostPage(btree, page);

		while ((offset = btree->findChildPtr(btree, page, stack->blkno, InvalidOffsetNumber)) == InvalidOffsetNumber)
		{
			blkno = GinPageGetOpaque(page)->rightlink;
			LockBuffer(buffer, GIN_UNLOCK);
			ReleaseBuffer(buffer);
			if (blkno == InvalidBlockNumber)
				break;
			buffer = ReadBuffer(btree->index, blkno);
			LockBuffer(buffer, GIN_EXCLUSIVE);
			page = BufferGetPage(buffer);
		}

		if (blkno != InvalidBlockNumber)
		{
			ptr = (GinBtreeStack *) palloc(sizeof(GinBtreeStack));
			ptr->blkno = blkno;
			ptr->buffer = buffer;
			ptr->parent = root; /* it's may be wrong, but in next call we will
								 * correct */
			ptr->off = offset;
			stack->parent = ptr;
			return;
		}

		blkno = leftmostBlkno;
	}
}

/*
 * Find correct tuple in non-leaf page. It supposed that
 * page correctly choosen and searching value SHOULD be on page
 */
static BlockNumber
entryLocateEntry(GinBtree btree, GinBtreeStack *stack)
{
	OffsetNumber low,
				high,
				maxoff;
	IndexTuple	itup = NULL;
	int			result;
	Page		page = BufferGetPage(stack->buffer);

	Assert(!GinPageIsLeaf(page));
	Assert(!GinPageIsData(page));

	if (btree->fullScan)
	{
		stack->off = FirstOffsetNumber;
		stack->predictNumber *= PageGetMaxOffsetNumber(page);
		return btree->getLeftMostPage(btree, page);
	}

	low = FirstOffsetNumber;
	maxoff = high = PageGetMaxOffsetNumber(page);
	Assert(high >= low);

	high++;

	while (high > low)
	{
		OffsetNumber mid = low + ((high - low) / 2);

		if (mid == maxoff && GinPageRightMost(page))
			/* Right infinity */
			result = -1;
		else
		{
			itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, mid));
			result = compareAttEntries(btree->ginstate,
									   btree->entryAttnum, btree->entryValue,
								 gintuple_get_attrnum(btree->ginstate, itup),
								   gin_index_getattr(btree->ginstate, itup));
		}

		if (result == 0)
		{
			stack->off = mid;
			Assert(GinItemPointerGetBlockNumber(&(itup)->t_tid) != GIN_ROOT_BLKNO);
			return GinItemPointerGetBlockNumber(&(itup)->t_tid);
		}
		else if (result > 0)
			low = mid + 1;
		else
			high = mid;
	}

	Assert(high >= FirstOffsetNumber && high <= maxoff);

	stack->off = high;
	itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, high));
	Assert(GinItemPointerGetBlockNumber(&(itup)->t_tid) != GIN_ROOT_BLKNO);
	return GinItemPointerGetBlockNumber(&(itup)->t_tid);
}