/*
 * Form a non-leaf entry tuple by copying the key data from the given tuple,
 * which can be either a leaf or non-leaf entry tuple.
 *
 * Any posting list in the source tuple is not copied.  The specified child
 * block number is inserted into t_tid.
 */
static IndexTuple
GinFormInteriorTuple(IndexTuple itup, Page page, BlockNumber childblk)
{
	IndexTuple	nitup;

	if (GinPageIsLeaf(page) && !GinIsPostingTree(itup))
	{
		/* Tuple contains a posting list, just copy stuff before that */
		uint32		origsize = GinGetPostingOffset(itup);

		origsize = MAXALIGN(origsize);
		nitup = (IndexTuple) palloc(origsize);
		memcpy(nitup, itup, origsize);
		/* ... be sure to fix the size header field ... */
		nitup->t_info &= ~INDEX_SIZE_MASK;
		nitup->t_info |= origsize;
	}
	else
	{
		/* Copy the tuple as-is */
		nitup = (IndexTuple) palloc(IndexTupleSize(itup));
		memcpy(nitup, itup, IndexTupleSize(itup));
	}

	/* Now insert the correct downlink */
	GinSetDownlink(nitup, childblk);

	return nitup;
}

static bool
entryIsEnoughSpace(GinBtree btree, Buffer buf, OffsetNumber off,
				   GinBtreeEntryInsertData *insertData)
{
	Size		releasedsz = 0;
	Size		addedsz;
	Page		page = BufferGetPage(buf);

	Assert(insertData->entry);
	Assert(!GinPageIsData(page));

	if (insertData->isDelete)
	{
		IndexTuple	itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, off));

		releasedsz = MAXALIGN(IndexTupleSize(itup)) + sizeof(ItemIdData);
	}

	addedsz = MAXALIGN(IndexTupleSize(insertData->entry)) + sizeof(ItemIdData);

	if (PageGetFreeSpace(page) + releasedsz >= addedsz)
		return true;

	return false;
}

/*
 * Place tuple on page and fills WAL record
 */
static void
entryPlaceToPage(GinBtree btree, Buffer buf, OffsetNumber off, XLogRecData **prdata)
{
	Page		page = BufferGetPage(buf);
	static XLogRecData rdata[3];
	OffsetNumber placed;
	static ginxlogInsert data;
	int			cnt = 0;

	*prdata = rdata;
	data.updateBlkno = entryPreparePage(btree, page, off);

	placed = PageAddItem(page, (Item) btree->entry, IndexTupleSize(btree->entry), off, false, false);
	if (placed != off)
		elog(ERROR, "failed to add item to index page in \"%s\"",
			 RelationGetRelationName(btree->index));

	data.node = btree->index->rd_node;
	data.blkno = BufferGetBlockNumber(buf);
	data.offset = off;
	data.nitem = 1;
	data.isDelete = btree->isDelete;
	data.isData = false;
	data.isLeaf = GinPageIsLeaf(page) ? TRUE : FALSE;

	/*
	 * Prevent full page write if child's split occurs. That is needed to
	 * remove incomplete splits while replaying WAL
	 *
	 * data.updateBlkno contains new block number (of newly created right
	 * page) for recently splited page.
	 */
	if (data.updateBlkno == InvalidBlockNumber)
	{
		rdata[0].buffer = buf;
		rdata[0].buffer_std = TRUE;
		rdata[0].data = NULL;
		rdata[0].len = 0;
		rdata[0].next = &rdata[1];
		cnt++;
	}

	rdata[cnt].buffer = InvalidBuffer;
	rdata[cnt].data = (char *) &data;
	rdata[cnt].len = sizeof(ginxlogInsert);
	rdata[cnt].next = &rdata[cnt + 1];
	cnt++;

	rdata[cnt].buffer = InvalidBuffer;
	rdata[cnt].data = (char *) btree->entry;
	rdata[cnt].len = IndexTupleSize(btree->entry);
	rdata[cnt].next = NULL;

	btree->entry = NULL;
}

/*
 * Place tuple on page and fills WAL record
 *
 * If the tuple doesn't fit, returns false without modifying the page.
 *
 * On insertion to an internal node, in addition to inserting the given item,
 * the downlink of the existing item at 'off' is updated to point to
 * 'updateblkno'.
 */
static GinPlaceToPageRC
entryPlaceToPage(GinBtree btree, Buffer buf, GinBtreeStack *stack,
				 void *insertPayload, BlockNumber updateblkno,
				 XLogRecData **prdata, Page *newlpage, Page *newrpage)
{
	GinBtreeEntryInsertData *insertData = insertPayload;
	Page		page = BufferGetPage(buf);
	OffsetNumber off = stack->off;
	OffsetNumber placed;
	int			cnt = 0;

	/* these must be static so they can be returned to caller */
	static XLogRecData rdata[3];
	static ginxlogInsertEntry data;

	/* quick exit if it doesn't fit */
	if (!entryIsEnoughSpace(btree, buf, off, insertData))
	{
		entrySplitPage(btree, buf, stack, insertPayload, updateblkno,
					   prdata, newlpage, newrpage);
		return SPLIT;
	}

	START_CRIT_SECTION();

	*prdata = rdata;
	entryPreparePage(btree, page, off, insertData, updateblkno);

	placed = PageAddItem(page,
						 (Item) insertData->entry,
						 IndexTupleSize(insertData->entry),
						 off, false, false);
	if (placed != off)
		elog(ERROR, "failed to add item to index page in \"%s\"",
			 RelationGetRelationName(btree->index));

	data.isDelete = insertData->isDelete;
	data.offset = off;

	rdata[cnt].buffer = buf;
	rdata[cnt].buffer_std = true;
	rdata[cnt].data = (char *) &data;
	rdata[cnt].len = offsetof(ginxlogInsertEntry, tuple);
	rdata[cnt].next = &rdata[cnt + 1];
	cnt++;

	rdata[cnt].buffer = buf;
	rdata[cnt].buffer_std = true;
	rdata[cnt].data = (char *) insertData->entry;
	rdata[cnt].len = IndexTupleSize(insertData->entry);
	rdata[cnt].next = NULL;

	return INSERTED;
}

/*
 * Place tuple on page and fills WAL record
 *
 * If the tuple doesn't fit, returns false without modifying the page.
 *
 * On insertion to an internal node, in addition to inserting the given item,
 * the downlink of the existing item at 'off' is updated to point to
 * 'updateblkno'.
 *
 * On INSERTED, registers the buffer as buffer ID 0, with data.
 * On SPLIT, returns rdata that represents the split pages in *prdata.
 */
static GinPlaceToPageRC
entryPlaceToPage(GinBtree btree, Buffer buf, GinBtreeStack *stack,
				 void *insertPayload, BlockNumber updateblkno,
				 Page *newlpage, Page *newrpage)
{
	GinBtreeEntryInsertData *insertData = insertPayload;
	Page		page = BufferGetPage(buf, NULL, NULL, BGP_NO_SNAPSHOT_TEST);
	OffsetNumber off = stack->off;
	OffsetNumber placed;

	/* this must be static so it can be returned to caller. */
	static ginxlogInsertEntry data;

	/* quick exit if it doesn't fit */
	if (!entryIsEnoughSpace(btree, buf, off, insertData))
	{
		entrySplitPage(btree, buf, stack, insertPayload, updateblkno,
					   newlpage, newrpage);
		return SPLIT;
	}

	START_CRIT_SECTION();

	entryPreparePage(btree, page, off, insertData, updateblkno);

	placed = PageAddItem(page,
						 (Item) insertData->entry,
						 IndexTupleSize(insertData->entry),
						 off, false, false);
	if (placed != off)
		elog(ERROR, "failed to add item to index page in \"%s\"",
			 RelationGetRelationName(btree->index));

	if (RelationNeedsWAL(btree->index))
	{
		data.isDelete = insertData->isDelete;
		data.offset = off;

		XLogBeginInsert();
		XLogRegisterBuffer(0, buf, REGBUF_STANDARD);
		XLogRegisterBufData(0, (char *) &data,
							offsetof(ginxlogInsertEntry, tuple));
		XLogRegisterBufData(0, (char *) insertData->entry,
							IndexTupleSize(insertData->entry));
	}

	return INSERTED;
}

/*
 * Inserts only one entry to the index, but it can add more than 1 ItemPointer.
 */
static void
ginEntryInsert(Relation index, GinState *ginstate, Datum value, ItemPointerData *items, uint32 nitem, bool isBuild)
{
	GinBtreeData btree;
	GinBtreeStack *stack;
	IndexTuple	itup;
	Page		page;

	prepareEntryScan(&btree, index, value, ginstate);

	stack = ginFindLeafPage(&btree, NULL);
	page = BufferGetPage(stack->buffer);

	if (btree.findItem(&btree, stack))
	{
		/* found entry */
		itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, stack->off));

		if (GinIsPostingTree(itup))
		{
			/* lock root of posting tree */
			GinPostingTreeScan *gdi;
			BlockNumber rootPostingTree = GinGetPostingTree(itup);

			/* release all stack */
			LockBuffer(stack->buffer, GIN_UNLOCK);
			freeGinBtreeStack(stack);

			/* insert into posting tree */
			gdi = prepareScanPostingTree(index, rootPostingTree, FALSE);
			gdi->btree.isBuild = isBuild;
			insertItemPointer(gdi, items, nitem);

			return;
		}

		itup = addItemPointersToTuple(index, ginstate, stack, itup, items, nitem, isBuild);

		btree.isDelete = TRUE;
	}
	else
	{
		/* We suppose, that tuple can store at list one itempointer */
		itup = GinFormTuple(ginstate, value, items, 1);
		if (itup == NULL || IndexTupleSize(itup) >= GinMaxItemSize)
			elog(ERROR, "huge tuple");

		if (nitem > 1)
		{
			IndexTuple	previtup = itup;

			itup = addItemPointersToTuple(index, ginstate, stack, previtup, items + 1, nitem - 1, isBuild);
			pfree(previtup);
		}
	}

	btree.entry = itup;
	ginInsertValue(&btree, stack);
	pfree(itup);
}

/*
 * Fills new root by rightest values from child.
 * Also called from rumxlog, should not use btree
 */
void
rumEntryFillRoot(RumBtree btree, Buffer root, Buffer lbuf, Buffer rbuf,
				 Page page, Page lpage, Page rpage)
{
	IndexTuple	itup;

	itup = rumPageGetLinkItup(btree, lbuf, lpage);
	if (PageAddItem(page, (Item) itup, IndexTupleSize(itup), InvalidOffsetNumber, false, false) == InvalidOffsetNumber)
		elog(ERROR, "failed to add item to index root page");
	pfree(itup);

	itup = rumPageGetLinkItup(btree, rbuf, rpage);
	if (PageAddItem(page, (Item) itup, IndexTupleSize(itup), InvalidOffsetNumber, false, false) == InvalidOffsetNumber)
		elog(ERROR, "failed to add item to index root page");
	pfree(itup);
}

static void
decodePageSplitRecord(PageSplitRecord *decoded, XLogRecord *record)
{
	char	   *begin = XLogRecGetData(record),
			   *ptr;
	int			j,
				i = 0;

	decoded->data = (gistxlogPageSplit *) begin;
	decoded->page = (NewPage *) palloc(sizeof(NewPage) * decoded->data->npage);

	ptr = begin + sizeof(gistxlogPageSplit);
	for (i = 0; i < decoded->data->npage; i++)
	{
		Assert(ptr - begin < record->xl_len);
		decoded->page[i].header = (gistxlogPage *) ptr;
		ptr += sizeof(gistxlogPage);

		decoded->page[i].itup = (IndexTuple *)
			palloc(sizeof(IndexTuple) * decoded->page[i].header->num);
		j = 0;
		while (j < decoded->page[i].header->num)
		{
			Assert(ptr - begin < record->xl_len);
			decoded->page[i].itup[j] = (IndexTuple) ptr;
			ptr += IndexTupleSize((IndexTuple) ptr);
			j++;
		}
	}
}

/*
 * Write XLOG record describing a page update. The update can include any
 * number of deletions and/or insertions of tuples on a single index page.
 *
 * If this update inserts a downlink for a split page, also record that
 * the F_FOLLOW_RIGHT flag on the child page is cleared and NSN set.
 *
 * Note that both the todelete array and the tuples are marked as belonging
 * to the target buffer; they need not be stored in XLOG if XLogInsert decides
 * to log the whole buffer contents instead.
 */
XLogRecPtr
gistXLogUpdate(Buffer buffer,
			   OffsetNumber *todelete, int ntodelete,
			   IndexTuple *itup, int ituplen,
			   Buffer leftchildbuf)
{
	gistxlogPageUpdate xlrec;
	int			i;
	XLogRecPtr	recptr;

	xlrec.ntodelete = ntodelete;
	xlrec.ntoinsert = ituplen;

	XLogBeginInsert();
	XLogRegisterData((char *) &xlrec, sizeof(gistxlogPageUpdate));

	XLogRegisterBuffer(0, buffer, REGBUF_STANDARD);
	XLogRegisterBufData(0, (char *) todelete, sizeof(OffsetNumber) * ntodelete);

	/* new tuples */
	for (i = 0; i < ituplen; i++)
		XLogRegisterBufData(0, (char *) (itup[i]), IndexTupleSize(itup[i]));

	/*
	 * Include a full page image of the child buf. (only necessary if a
	 * checkpoint happened since the child page was split)
	 */
	if (BufferIsValid(leftchildbuf))
		XLogRegisterBuffer(1, leftchildbuf, REGBUF_STANDARD);

	recptr = XLogInsert(RM_GIST_ID, XLOG_GIST_PAGE_UPDATE);

	return recptr;
}

/*
 * _hash_formitem -- construct a hash index entry
 */
HashItem
_hash_formitem(IndexTuple itup)
{
	int			nbytes_hitem;
	HashItem	hitem;
	Size		tuplen;

	/* disallow nulls in hash keys */
	if (IndexTupleHasNulls(itup))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("hash indexes cannot contain null keys")));

	/*
	 * make a copy of the index tuple (XXX do we still need to copy?)
	 *
	 * HashItemData used to have more fields than IndexTupleData, but no
	 * longer...
	 */
	tuplen = IndexTupleSize(itup);
	nbytes_hitem = tuplen +
		(sizeof(HashItemData) - sizeof(IndexTupleData));

	hitem = (HashItem) palloc(nbytes_hitem);
	memcpy((char *) &(hitem->hash_itup), (char *) itup, tuplen);

	return hitem;
}

/*
 * Fills new root by rightest values from child.
 * Also called from ginxlog, should not use btree
 */
void
entryFillRoot(GinBtree btree, Buffer root, Buffer lbuf, Buffer rbuf)
{
	Page		page;
	IndexTuple	itup;

	page = BufferGetPage(root);

	itup = ginPageGetLinkItup(lbuf);
	if (PageAddItem(page, (Item) itup, IndexTupleSize(itup), InvalidOffsetNumber, false, false) == InvalidOffsetNumber)
		elog(ERROR, "failed to add item to index root page");

	itup = ginPageGetLinkItup(rbuf);
	if (PageAddItem(page, (Item) itup, IndexTupleSize(itup), InvalidOffsetNumber, false, false) == InvalidOffsetNumber)
		elog(ERROR, "failed to add item to index root page");
}

/*
 * Fills new root by rightest values from child.
 * Also called from ginxlog, should not use btree
 */
void
ginEntryFillRoot(GinBtree btree, Page root,
				 BlockNumber lblkno, Page lpage,
				 BlockNumber rblkno, Page rpage)
{
	IndexTuple	itup;

	itup = GinFormInteriorTuple(getRightMostTuple(lpage), lpage, lblkno);
	if (PageAddItem(root, (Item) itup, IndexTupleSize(itup), InvalidOffsetNumber, false, false) == InvalidOffsetNumber)
		elog(ERROR, "failed to add item to index root page");
	pfree(itup);

	itup = GinFormInteriorTuple(getRightMostTuple(rpage), rpage, rblkno);
	if (PageAddItem(root, (Item) itup, IndexTupleSize(itup), InvalidOffsetNumber, false, false) == InvalidOffsetNumber)
		elog(ERROR, "failed to add item to index root page");
	pfree(itup);
}

/*
 * Form a tuple for entry tree.
 *
 * On leaf pages, Index tuple has non-traditional layout. Tuple may contain
 * posting list or root blocknumber of posting tree.
 * Macros: GinIsPostingTree(itup) / GinSetPostingTree(itup, blkno)
 * 1) Posting list
 *		- itup->t_info & INDEX_SIZE_MASK contains total size of tuple as usual
 *		- ItemPointerGetBlockNumber(&itup->t_tid) contains original
 *		  size of tuple (without posting list).
 *		  Macros: GinGetOrigSizePosting(itup) / GinSetOrigSizePosting(itup,n)
 *		- ItemPointerGetOffsetNumber(&itup->t_tid) contains number
 *		  of elements in posting list (number of heap itempointers)
 *		  Macros: GinGetNPosting(itup) / GinSetNPosting(itup,n)
 *		- After standard part of tuple there is a posting list, ie, array
 *		  of heap itempointers
 *		  Macros: GinGetPosting(itup)
 * 2) Posting tree
 *		- itup->t_info & INDEX_SIZE_MASK contains size of tuple as usual
 *		- ItemPointerGetBlockNumber(&itup->t_tid) contains block number of
 *		  root of posting tree
 *		- ItemPointerGetOffsetNumber(&itup->t_tid) contains magic number
 *		  GIN_TREE_POSTING, which distinguishes this from posting-list case
 *
 * Attributes of an index tuple are different for single and multicolumn index.
 * For single-column case, index tuple stores only value to be indexed.
 * For multicolumn case, it stores two attributes: column number of value
 * and value.
 */
IndexTuple
GinFormTuple(GinState *ginstate, OffsetNumber attnum, Datum key, ItemPointerData *ipd, uint32 nipd)
{
	bool		isnull[2] = {FALSE, FALSE};
	IndexTuple	itup;

	if (ginstate->oneCol)
		itup = index_form_tuple(ginstate->origTupdesc, &key, isnull);
	else
	{
		Datum		datums[2];

		datums[0] = UInt16GetDatum(attnum);
		datums[1] = key;
		itup = index_form_tuple(ginstate->tupdesc[attnum - 1], datums, isnull);
	}

	GinSetOrigSizePosting(itup, IndexTupleSize(itup));

	if (nipd > 0)
	{
		uint32		newsize = MAXALIGN(SHORTALIGN(IndexTupleSize(itup)) + sizeof(ItemPointerData) * nipd);

		if (newsize >= INDEX_SIZE_MASK)
			return NULL;

		if (newsize > TOAST_INDEX_TARGET && nipd > 1)
			return NULL;

		itup = repalloc(itup, newsize);

		/* set new size */
		itup->t_info &= ~INDEX_SIZE_MASK;
		itup->t_info |= newsize;

		if (ipd)
			memcpy(GinGetPosting(itup), ipd, sizeof(ItemPointerData) * nipd);
		GinSetNPosting(itup, nipd);
	}
	else
	{
		GinSetNPosting(itup, 0);
	}
	return itup;
}

/*
 * Check space for itup vector on page
 */
bool
gistnospace(Page page, IndexTuple *itvec, int len, OffsetNumber todelete, Size freespace)
{
	unsigned int size = freespace,
				deleted = 0;
	int			i;

	for (i = 0; i < len; i++)
		size += IndexTupleSize(itvec[i]) + sizeof(ItemIdData);

	if (todelete != InvalidOffsetNumber)
	{
		IndexTuple	itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, todelete));

		deleted = IndexTupleSize(itup) + sizeof(ItemIdData);
	}

	return (PageGetFreeSpace(page) + deleted < size);
}

static void
ginRedoInsertListPage(XLogReaderState *record)
{
	XLogRecPtr	lsn = record->EndRecPtr;
	ginxlogInsertListPage *data = (ginxlogInsertListPage *) XLogRecGetData(record);
	Buffer		buffer;
	Page		page;
	OffsetNumber l,
				off = FirstOffsetNumber;
	int			i,
				tupsize;
	char	   *payload;
	IndexTuple	tuples;
	Size		totaltupsize;

	/* We always re-initialize the page. */
	buffer = XLogInitBufferForRedo(record, 0);
	page = BufferGetPage(buffer);

	GinInitBuffer(buffer, GIN_LIST);
	GinPageGetOpaque(page)->rightlink = data->rightlink;
	if (data->rightlink == InvalidBlockNumber)
	{
		/* tail of sublist */
		GinPageSetFullRow(page);
		GinPageGetOpaque(page)->maxoff = 1;
	}
	else
	{
		GinPageGetOpaque(page)->maxoff = 0;
	}

	payload = XLogRecGetBlockData(record, 0, &totaltupsize);

	tuples = (IndexTuple) payload;
	for (i = 0; i < data->ntuples; i++)
	{
		tupsize = IndexTupleSize(tuples);

		l = PageAddItem(page, (Item) tuples, tupsize, off, false, false);

		if (l == InvalidOffsetNumber)
			elog(ERROR, "failed to add item to index page");

		tuples = (IndexTuple) (((char *) tuples) + tupsize);
		off++;
	}
	Assert((char *) tuples == payload + totaltupsize);

	PageSetLSN(page, lsn);
	MarkBufferDirty(buffer);

	UnlockReleaseBuffer(buffer);
}

/*
 * Check space for itup vector on page
 */
static int
gistnospace(Page page, IndexTuple *itvec, int len)
{
	unsigned int size = 0;
	int			i;

	for (i = 0; i < len; i++)
		size += IndexTupleSize(itvec[i]) + sizeof(ItemIdData);

	return (PageGetFreeSpace(page) < size);
}

/*
 * Returns new tuple with copied value from source tuple.
 * New tuple will not store posting list
 */
static IndexTuple
copyIndexTuple(IndexTuple itup, Page page)
{
	IndexTuple	nitup;

	if (GinPageIsLeaf(page) && !GinIsPostingTree(itup))
	{
		nitup = (IndexTuple) palloc(MAXALIGN(GinGetOrigSizePosting(itup)));
		memcpy(nitup, itup, GinGetOrigSizePosting(itup));
		nitup->t_info &= ~INDEX_SIZE_MASK;
		nitup->t_info |= GinGetOrigSizePosting(itup);
	}
	else
	{
		nitup = (IndexTuple) palloc(MAXALIGN(IndexTupleSize(itup)));
		memcpy(nitup, itup, IndexTupleSize(itup));
	}

	return nitup;
}

/*
 * Create a palloc'd copy of an index tuple.
 */
IndexTuple
CopyIndexTuple(IndexTuple source)
{
	IndexTuple	result;
	Size		size;

	size = IndexTupleSize(source);
	result = (IndexTuple) palloc(size);
	memcpy(result, source, size);
	return result;
}

static void
ginRedoSplitEntry(Page lpage, Page rpage, void *rdata)
{
    ginxlogSplitEntry *data = (ginxlogSplitEntry *) rdata;
    IndexTuple	itup = (IndexTuple) ((char *) rdata + sizeof(ginxlogSplitEntry));
    OffsetNumber i;

    for (i = 0; i < data->separator; i++)
    {
        if (PageAddItem(lpage, (Item) itup, IndexTupleSize(itup), InvalidOffsetNumber, false, false) == InvalidOffsetNumber)
            elog(ERROR, "failed to add item to gin index page");
        itup = (IndexTuple) (((char *) itup) + MAXALIGN(IndexTupleSize(itup)));
    }

    for (i = data->separator; i < data->nitem; i++)
    {
        if (PageAddItem(rpage, (Item) itup, IndexTupleSize(itup), InvalidOffsetNumber, false, false) == InvalidOffsetNumber)
            elog(ERROR, "failed to add item to gin index page");
        itup = (IndexTuple) (((char *) itup) + MAXALIGN(IndexTupleSize(itup)));
    }
}

static void
ginRedoInsertListPage(XLogRecPtr lsn, XLogRecord *record)
{
	ginxlogInsertListPage *data = (ginxlogInsertListPage *) XLogRecGetData(record);
	Buffer		buffer;
	Page		page;
	OffsetNumber l,
				off = FirstOffsetNumber;
	int			i,
				tupsize;
	IndexTuple	tuples = (IndexTuple) (XLogRecGetData(record) + sizeof(ginxlogInsertListPage));

	/* If we have a full-page image, restore it and we're done */
	if (record->xl_info & XLR_BKP_BLOCK(0))
	{
		(void) RestoreBackupBlock(lsn, record, 0, false, false);
		return;
	}

	buffer = XLogReadBuffer(data->node, data->blkno, true);
	Assert(BufferIsValid(buffer));
	page = BufferGetPage(buffer);

	GinInitBuffer(buffer, GIN_LIST);
	GinPageGetOpaque(page)->rightlink = data->rightlink;
	if (data->rightlink == InvalidBlockNumber)
	{
		/* tail of sublist */
		GinPageSetFullRow(page);
		GinPageGetOpaque(page)->maxoff = 1;
	}
	else
	{
		GinPageGetOpaque(page)->maxoff = 0;
	}

	for (i = 0; i < data->ntuples; i++)
	{
		tupsize = IndexTupleSize(tuples);

		l = PageAddItem(page, (Item) tuples, tupsize, off, false, false);

		if (l == InvalidOffsetNumber)
			elog(ERROR, "failed to add item to index page");

		tuples = (IndexTuple) (((char *) tuples) + tupsize);
	}

	PageSetLSN(page, lsn);
	MarkBufferDirty(buffer);

	UnlockReleaseBuffer(buffer);
}