C++ PageGetSpecialPointer函数代码示例

/*
 * replay addition of overflow page for hash index
 */
static void
hash_xlog_add_ovfl_page(XLogReaderState *record)
{
	XLogRecPtr	lsn = record->EndRecPtr;
	xl_hash_add_ovfl_page *xlrec = (xl_hash_add_ovfl_page *) XLogRecGetData(record);
	Buffer		leftbuf;
	Buffer		ovflbuf;
	Buffer		metabuf;
	BlockNumber leftblk;
	BlockNumber rightblk;
	BlockNumber newmapblk = InvalidBlockNumber;
	Page		ovflpage;
	HashPageOpaque ovflopaque;
	uint32	   *num_bucket;
	char	   *data;
	Size datalen PG_USED_FOR_ASSERTS_ONLY;
	bool		new_bmpage = false;

	XLogRecGetBlockTag(record, 0, NULL, NULL, &rightblk);
	XLogRecGetBlockTag(record, 1, NULL, NULL, &leftblk);

	ovflbuf = XLogInitBufferForRedo(record, 0);
	Assert(BufferIsValid(ovflbuf));

	data = XLogRecGetBlockData(record, 0, &datalen);
	num_bucket = (uint32 *) data;
	Assert(datalen == sizeof(uint32));
	_hash_initbuf(ovflbuf, InvalidBlockNumber, *num_bucket, LH_OVERFLOW_PAGE,
				  true);
	/* update backlink */
	ovflpage = BufferGetPage(ovflbuf);
	ovflopaque = (HashPageOpaque) PageGetSpecialPointer(ovflpage);
	ovflopaque->hasho_prevblkno = leftblk;

	PageSetLSN(ovflpage, lsn);
	MarkBufferDirty(ovflbuf);

	if (XLogReadBufferForRedo(record, 1, &leftbuf) == BLK_NEEDS_REDO)
	{
		Page		leftpage;
		HashPageOpaque leftopaque;

		leftpage = BufferGetPage(leftbuf);
		leftopaque = (HashPageOpaque) PageGetSpecialPointer(leftpage);
		leftopaque->hasho_nextblkno = rightblk;

		PageSetLSN(leftpage, lsn);
		MarkBufferDirty(leftbuf);
	}

	if (BufferIsValid(leftbuf))
		UnlockReleaseBuffer(leftbuf);
	UnlockReleaseBuffer(ovflbuf);

	/*
	 * Note: in normal operation, we'd update the bitmap and meta page while
	 * still holding lock on the overflow pages.  But during replay it's not
	 * necessary to hold those locks, since no other index updates can be
	 * happening concurrently.
	 */
	if (XLogRecHasBlockRef(record, 2))
	{
		Buffer		mapbuffer;

		if (XLogReadBufferForRedo(record, 2, &mapbuffer) == BLK_NEEDS_REDO)
		{
			Page		mappage = (Page) BufferGetPage(mapbuffer);
			uint32	   *freep = NULL;
			char	   *data;
			uint32	   *bitmap_page_bit;

			freep = HashPageGetBitmap(mappage);

			data = XLogRecGetBlockData(record, 2, &datalen);
			bitmap_page_bit = (uint32 *) data;

			SETBIT(freep, *bitmap_page_bit);

			PageSetLSN(mappage, lsn);
			MarkBufferDirty(mapbuffer);
		}
		if (BufferIsValid(mapbuffer))
			UnlockReleaseBuffer(mapbuffer);
	}

	if (XLogRecHasBlockRef(record, 3))
	{
		Buffer		newmapbuf;

		newmapbuf = XLogInitBufferForRedo(record, 3);

		_hash_initbitmapbuffer(newmapbuf, xlrec->bmsize, true);

		new_bmpage = true;
		newmapblk = BufferGetBlockNumber(newmapbuf);

		MarkBufferDirty(newmapbuf);
//.........这里部分代码省略.........

/*
 *	_hash_freeovflpage() -
 *
 *	Remove this overflow page from its bucket's chain, and mark the page as
 *	free.  On entry, ovflbuf is write-locked; it is released before exiting.
 *
 *	Since this function is invoked in VACUUM, we provide an access strategy
 *	parameter that controls fetches of the bucket pages.
 *
 *	Returns the block number of the page that followed the given page
 *	in the bucket, or InvalidBlockNumber if no following page.
 *
 *	NB: caller must not hold lock on metapage, nor on either page that's
 *	adjacent in the bucket chain.  The caller had better hold exclusive lock
 *	on the bucket, too.
 */
BlockNumber
_hash_freeovflpage(Relation rel, Buffer ovflbuf,
				   BufferAccessStrategy bstrategy)
{
	HashMetaPage metap;
	Buffer		metabuf;
	Buffer		mapbuf;
	BlockNumber ovflblkno;
	BlockNumber prevblkno;
	BlockNumber blkno;
	BlockNumber nextblkno;
	HashPageOpaque ovflopaque;
	Page		ovflpage;
	Page		mappage;
	uint32	   *freep;
	uint32		ovflbitno;
	int32		bitmappage,
				bitmapbit;
	Bucket bucket PG_USED_FOR_ASSERTS_ONLY;

	/* Get information from the doomed page */
	_hash_checkpage(rel, ovflbuf, LH_OVERFLOW_PAGE);
	ovflblkno = BufferGetBlockNumber(ovflbuf);
	ovflpage = BufferGetPage(ovflbuf);
	ovflopaque = (HashPageOpaque) PageGetSpecialPointer(ovflpage);
	nextblkno = ovflopaque->hasho_nextblkno;
	prevblkno = ovflopaque->hasho_prevblkno;
	bucket = ovflopaque->hasho_bucket;

	/*
	 * Zero the page for debugging's sake; then write and release it. (Note:
	 * if we failed to zero the page here, we'd have problems with the Assert
	 * in _hash_pageinit() when the page is reused.)
	 */
	MemSet(ovflpage, 0, BufferGetPageSize(ovflbuf));
	_hash_wrtbuf(rel, ovflbuf);

	/*
	 * Fix up the bucket chain.  this is a doubly-linked list, so we must fix
	 * up the bucket chain members behind and ahead of the overflow page being
	 * deleted.  No concurrency issues since we hold exclusive lock on the
	 * entire bucket.
	 */
	if (BlockNumberIsValid(prevblkno))
	{
		Buffer		prevbuf = _hash_getbuf_with_strategy(rel,
														 prevblkno,
														 HASH_WRITE,
										   LH_BUCKET_PAGE | LH_OVERFLOW_PAGE,
														 bstrategy);
		Page		prevpage = BufferGetPage(prevbuf);
		HashPageOpaque prevopaque = (HashPageOpaque) PageGetSpecialPointer(prevpage);

		Assert(prevopaque->hasho_bucket == bucket);
		prevopaque->hasho_nextblkno = nextblkno;
		_hash_wrtbuf(rel, prevbuf);
	}
	if (BlockNumberIsValid(nextblkno))
	{
		Buffer		nextbuf = _hash_getbuf_with_strategy(rel,
														 nextblkno,
														 HASH_WRITE,
														 LH_OVERFLOW_PAGE,
														 bstrategy);
		Page		nextpage = BufferGetPage(nextbuf);
		HashPageOpaque nextopaque = (HashPageOpaque) PageGetSpecialPointer(nextpage);

		Assert(nextopaque->hasho_bucket == bucket);
		nextopaque->hasho_prevblkno = prevblkno;
		_hash_wrtbuf(rel, nextbuf);
	}

	/* Note: bstrategy is intentionally not used for metapage and bitmap */

	/* Read the metapage so we can determine which bitmap page to use */
	metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_READ, LH_META_PAGE);
	metap = HashPageGetMeta(BufferGetPage(metabuf));

	/* Identify which bit to set */
	ovflbitno = blkno_to_bitno(metap, ovflblkno);

	bitmappage = ovflbitno >> BMPG_SHIFT(metap);
	bitmapbit = ovflbitno & BMPG_MASK(metap);

//.........这里部分代码省略.........

/*
 * Bulk deletion of all index entries pointing to a set of heap tuples.
 * The set of target tuples is specified via a callback routine that tells
 * whether any given heap tuple (identified by ItemPointer) is being deleted.
 *
 * This function also deletes the tuples that are moved by split to other
 * bucket.
 *
 * Result: a palloc'd struct containing statistical info for VACUUM displays.
 */
IndexBulkDeleteResult *
hashbulkdelete(IndexVacuumInfo *info, IndexBulkDeleteResult *stats,
			   IndexBulkDeleteCallback callback, void *callback_state)
{
	Relation	rel = info->index;
	double		tuples_removed;
	double		num_index_tuples;
	double		orig_ntuples;
	Bucket		orig_maxbucket;
	Bucket		cur_maxbucket;
	Bucket		cur_bucket;
	Buffer		metabuf = InvalidBuffer;
	HashMetaPage metap;
	HashMetaPage cachedmetap;

	tuples_removed = 0;
	num_index_tuples = 0;

	/*
	 * We need a copy of the metapage so that we can use its hashm_spares[]
	 * values to compute bucket page addresses, but a cached copy should be
	 * good enough.  (If not, we'll detect that further down and refresh the
	 * cache as necessary.)
	 */
	cachedmetap = _hash_getcachedmetap(rel, &metabuf, false);
	Assert(cachedmetap != NULL);

	orig_maxbucket = cachedmetap->hashm_maxbucket;
	orig_ntuples = cachedmetap->hashm_ntuples;

	/* Scan the buckets that we know exist */
	cur_bucket = 0;
	cur_maxbucket = orig_maxbucket;

loop_top:
	while (cur_bucket <= cur_maxbucket)
	{
		BlockNumber bucket_blkno;
		BlockNumber blkno;
		Buffer		bucket_buf;
		Buffer		buf;
		HashPageOpaque bucket_opaque;
		Page		page;
		bool		split_cleanup = false;

		/* Get address of bucket's start page */
		bucket_blkno = BUCKET_TO_BLKNO(cachedmetap, cur_bucket);

		blkno = bucket_blkno;

		/*
		 * We need to acquire a cleanup lock on the primary bucket page to out
		 * wait concurrent scans before deleting the dead tuples.
		 */
		buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL, info->strategy);
		LockBufferForCleanup(buf);
		_hash_checkpage(rel, buf, LH_BUCKET_PAGE);

		page = BufferGetPage(buf);
		bucket_opaque = (HashPageOpaque) PageGetSpecialPointer(page);

		/*
		 * If the bucket contains tuples that are moved by split, then we need
		 * to delete such tuples.  We can't delete such tuples if the split
		 * operation on bucket is not finished as those are needed by scans.
		 */
		if (!H_BUCKET_BEING_SPLIT(bucket_opaque) &&
			H_NEEDS_SPLIT_CLEANUP(bucket_opaque))
		{
			split_cleanup = true;

			/*
			 * This bucket might have been split since we last held a lock on
			 * the metapage.  If so, hashm_maxbucket, hashm_highmask and
			 * hashm_lowmask might be old enough to cause us to fail to remove
			 * tuples left behind by the most recent split.  To prevent that,
			 * now that the primary page of the target bucket has been locked
			 * (and thus can't be further split), check whether we need to
			 * update our cached metapage data.
			 */
			Assert(bucket_opaque->hasho_prevblkno != InvalidBlockNumber);
			if (bucket_opaque->hasho_prevblkno > cachedmetap->hashm_maxbucket)
			{
				cachedmetap = _hash_getcachedmetap(rel, &metabuf, true);
				Assert(cachedmetap != NULL);
			}
		}

		bucket_buf = buf;

//.........这里部分代码省略.........

static void
btree_xlog_split(bool onleft, bool isroot, XLogReaderState *record)
{
	XLogRecPtr	lsn = record->EndRecPtr;
	xl_btree_split *xlrec = (xl_btree_split *) XLogRecGetData(record);
	bool		isleaf = (xlrec->level == 0);
	Buffer		lbuf;
	Buffer		rbuf;
	Page		rpage;
	BTPageOpaque ropaque;
	char	   *datapos;
	Size		datalen;
	Item		left_hikey = NULL;
	Size		left_hikeysz = 0;
	BlockNumber leftsib;
	BlockNumber rightsib;
	BlockNumber rnext;

	XLogRecGetBlockTag(record, 0, NULL, NULL, &leftsib);
	XLogRecGetBlockTag(record, 1, NULL, NULL, &rightsib);
	if (!XLogRecGetBlockTag(record, 2, NULL, NULL, &rnext))
		rnext = P_NONE;

	/*
	 * Clear the incomplete split flag on the left sibling of the child page
	 * this is a downlink for.  (Like in btree_xlog_insert, this can be done
	 * before locking the other pages)
	 */
	if (!isleaf)
		_bt_clear_incomplete_split(record, 3);

	/* Reconstruct right (new) sibling page from scratch */
	rbuf = XLogInitBufferForRedo(record, 1);
	datapos = XLogRecGetBlockData(record, 1, &datalen);
	rpage = (Page) BufferGetPage(rbuf);

	_bt_pageinit(rpage, BufferGetPageSize(rbuf));
	ropaque = (BTPageOpaque) PageGetSpecialPointer(rpage);

	ropaque->btpo_prev = leftsib;
	ropaque->btpo_next = rnext;
	ropaque->btpo.level = xlrec->level;
	ropaque->btpo_flags = isleaf ? BTP_LEAF : 0;
	ropaque->btpo_cycleid = 0;

	_bt_restore_page(rpage, datapos, datalen);

	/*
	 * On leaf level, the high key of the left page is equal to the first key
	 * on the right page.
	 */
	if (isleaf)
	{
		ItemId		hiItemId = PageGetItemId(rpage, P_FIRSTDATAKEY(ropaque));

		left_hikey = PageGetItem(rpage, hiItemId);
		left_hikeysz = ItemIdGetLength(hiItemId);
	}

	PageSetLSN(rpage, lsn);
	MarkBufferDirty(rbuf);

	/* don't release the buffer yet; we touch right page's first item below */

	/* Now reconstruct left (original) sibling page */
	if (XLogReadBufferForRedo(record, 0, &lbuf) == BLK_NEEDS_REDO)
	{
		/*
		 * To retain the same physical order of the tuples that they had, we
		 * initialize a temporary empty page for the left page and add all the
		 * items to that in item number order.  This mirrors how _bt_split()
		 * works.  It's not strictly required to retain the same physical
		 * order, as long as the items are in the correct item number order,
		 * but it helps debugging.  See also _bt_restore_page(), which does
		 * the same for the right page.
		 */
		Page		lpage = (Page) BufferGetPage(lbuf);
		BTPageOpaque lopaque = (BTPageOpaque) PageGetSpecialPointer(lpage);
		OffsetNumber off;
		Item		newitem = NULL;
		Size		newitemsz = 0;
		Page		newlpage;
		OffsetNumber leftoff;

		datapos = XLogRecGetBlockData(record, 0, &datalen);

		if (onleft)
		{
			newitem = (Item) datapos;
			newitemsz = MAXALIGN(IndexTupleSize(newitem));
			datapos += newitemsz;
			datalen -= newitemsz;
		}

		/* Extract left hikey and its size (assuming 16-bit alignment) */
		if (!isleaf)
		{
			left_hikey = (Item) datapos;
			left_hikeysz = MAXALIGN(IndexTupleSize(left_hikey));
			datapos += left_hikeysz;
//.........这里部分代码省略.........

static void
btree_xlog_mark_page_halfdead(uint8 info, XLogReaderState *record)
{
	XLogRecPtr	lsn = record->EndRecPtr;
	xl_btree_mark_page_halfdead *xlrec = (xl_btree_mark_page_halfdead *) XLogRecGetData(record);
	Buffer		buffer;
	Page		page;
	BTPageOpaque pageop;
	IndexTupleData trunctuple;

	/*
	 * In normal operation, we would lock all the pages this WAL record
	 * touches before changing any of them.  In WAL replay, it should be okay
	 * to lock just one page at a time, since no concurrent index updates can
	 * be happening, and readers should not care whether they arrive at the
	 * target page or not (since it's surely empty).
	 */

	/* parent page */
	if (XLogReadBufferForRedo(record, 1, &buffer) == BLK_NEEDS_REDO)
	{
		OffsetNumber poffset;
		ItemId		itemid;
		IndexTuple	itup;
		OffsetNumber nextoffset;
		BlockNumber rightsib;

		page = (Page) BufferGetPage(buffer);
		pageop = (BTPageOpaque) PageGetSpecialPointer(page);

		poffset = xlrec->poffset;

		nextoffset = OffsetNumberNext(poffset);
		itemid = PageGetItemId(page, nextoffset);
		itup = (IndexTuple) PageGetItem(page, itemid);
		rightsib = ItemPointerGetBlockNumber(&itup->t_tid);

		itemid = PageGetItemId(page, poffset);
		itup = (IndexTuple) PageGetItem(page, itemid);
		ItemPointerSet(&(itup->t_tid), rightsib, P_HIKEY);
		nextoffset = OffsetNumberNext(poffset);
		PageIndexTupleDelete(page, nextoffset);

		PageSetLSN(page, lsn);
		MarkBufferDirty(buffer);
	}
	if (BufferIsValid(buffer))
		UnlockReleaseBuffer(buffer);

	/* Rewrite the leaf page as a halfdead page */
	buffer = XLogInitBufferForRedo(record, 0);
	page = (Page) BufferGetPage(buffer);

	_bt_pageinit(page, BufferGetPageSize(buffer));
	pageop = (BTPageOpaque) PageGetSpecialPointer(page);

	pageop->btpo_prev = xlrec->leftblk;
	pageop->btpo_next = xlrec->rightblk;
	pageop->btpo.level = 0;
	pageop->btpo_flags = BTP_HALF_DEAD | BTP_LEAF;
	pageop->btpo_cycleid = 0;

	/*
	 * Construct a dummy hikey item that points to the next parent to be
	 * deleted (if any).
	 */
	MemSet(&trunctuple, 0, sizeof(IndexTupleData));
	trunctuple.t_info = sizeof(IndexTupleData);
	if (xlrec->topparent != InvalidBlockNumber)
		ItemPointerSet(&trunctuple.t_tid, xlrec->topparent, P_HIKEY);
	else
		ItemPointerSetInvalid(&trunctuple.t_tid);
	if (PageAddItem(page, (Item) &trunctuple, sizeof(IndexTupleData), P_HIKEY,
					false, false) == InvalidOffsetNumber)
		elog(ERROR, "could not add dummy high key to half-dead page");

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

Datum
bt_page_items(PG_FUNCTION_ARGS)
{
	text	   *relname = PG_GETARG_TEXT_P(0);
	uint32		blkno = PG_GETARG_UINT32(1);
	Datum		result;
	char	   *values[6];
	HeapTuple	tuple;
	FuncCallContext *fctx;
	MemoryContext mctx;
	struct user_args *uargs;

	if (!superuser())
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 (errmsg("must be superuser to use pageinspect functions"))));

	if (SRF_IS_FIRSTCALL())
	{
		RangeVar   *relrv;
		Relation	rel;
		Buffer		buffer;
		BTPageOpaque opaque;
		TupleDesc	tupleDesc;

		fctx = SRF_FIRSTCALL_INIT();

		relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
		rel = relation_openrv(relrv, AccessShareLock);

		if (!IS_INDEX(rel) || !IS_BTREE(rel))
			elog(ERROR, "relation \"%s\" is not a btree index",
				 RelationGetRelationName(rel));

		/*
		 * Reject attempts to read non-local temporary relations; we would be
		 * likely to get wrong data since we have no visibility into the
		 * owning session's local buffers.
		 */
		if (RELATION_IS_OTHER_TEMP(rel))
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				errmsg("cannot access temporary tables of other sessions")));

		if (blkno == 0)
			elog(ERROR, "block 0 is a meta page");

		CHECK_RELATION_BLOCK_RANGE(rel, blkno);

		buffer = ReadBuffer(rel, blkno);
		LockBuffer(buffer, BUFFER_LOCK_SHARE);

		/*
		 * We copy the page into local storage to avoid holding pin on the
		 * buffer longer than we must, and possibly failing to release it at
		 * all if the calling query doesn't fetch all rows.
		 */
		mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);

		uargs = palloc(sizeof(struct user_args));

		uargs->page = palloc(BLCKSZ);
		memcpy(uargs->page, BufferGetPage(buffer), BLCKSZ);

		UnlockReleaseBuffer(buffer);
		relation_close(rel, AccessShareLock);

		uargs->offset = FirstOffsetNumber;

		opaque = (BTPageOpaque) PageGetSpecialPointer(uargs->page);

		if (P_ISDELETED(opaque))
			elog(NOTICE, "page is deleted");

		fctx->max_calls = PageGetMaxOffsetNumber(uargs->page);

		/* Build a tuple descriptor for our result type */
		if (get_call_result_type(fcinfo, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
			elog(ERROR, "return type must be a row type");

		fctx->attinmeta = TupleDescGetAttInMetadata(tupleDesc);

		fctx->user_fctx = uargs;

		MemoryContextSwitchTo(mctx);
	}

	fctx = SRF_PERCALL_SETUP();
	uargs = fctx->user_fctx;

	if (fctx->call_cntr < fctx->max_calls)
	{
		ItemId		id;
		IndexTuple	itup;
		int			j;
		int			off;
		int			dlen;
		char	   *dump;
		char	   *ptr;

//.........这里部分代码省略.........

/*
 *	_hash_metapinit() -- Initialize the metadata page of a hash index,
 *				the two buckets that we begin with and the initial
 *				bitmap page.
 *
 * We are fairly cavalier about locking here, since we know that no one else
 * could be accessing this index.  In particular the rule about not holding
 * multiple buffer locks is ignored.
 */
void
_hash_metapinit(Relation rel)
{
	HashMetaPage metap;
	HashPageOpaque pageopaque;
	Buffer		metabuf;
	Buffer		buf;
	Page		pg;
	int32		data_width;
	int32		item_width;
	int32		ffactor;
	uint16		i;

	/* safety check */
	if (RelationGetNumberOfBlocks(rel) != 0)
		elog(ERROR, "cannot initialize non-empty hash index \"%s\"",
			 RelationGetRelationName(rel));

	/*
	 * Determine the target fill factor (tuples per bucket) for this index.
	 * The idea is to make the fill factor correspond to pages about 3/4ths
	 * full.  We can compute it exactly if the index datatype is fixed-width,
	 * but for var-width there's some guessing involved.
	 */
	data_width = get_typavgwidth(RelationGetDescr(rel)->attrs[0]->atttypid,
								 RelationGetDescr(rel)->attrs[0]->atttypmod);
	item_width = MAXALIGN(sizeof(HashItemData)) + MAXALIGN(data_width) +
		sizeof(ItemIdData);		/* include the line pointer */
	ffactor = (BLCKSZ * 3 / 4) / item_width;
	/* keep to a sane range */
	if (ffactor < 10)
		ffactor = 10;

	metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_WRITE);
	pg = BufferGetPage(metabuf);
	_hash_pageinit(pg, BufferGetPageSize(metabuf));

	pageopaque = (HashPageOpaque) PageGetSpecialPointer(pg);
	pageopaque->hasho_prevblkno = InvalidBlockNumber;
	pageopaque->hasho_nextblkno = InvalidBlockNumber;
	pageopaque->hasho_bucket = -1;
	pageopaque->hasho_flag = LH_META_PAGE;
	pageopaque->hasho_filler = HASHO_FILL;

	metap = (HashMetaPage) pg;

	metap->hashm_magic = HASH_MAGIC;
	metap->hashm_version = HASH_VERSION;
	metap->hashm_ntuples = 0;
	metap->hashm_nmaps = 0;
	metap->hashm_ffactor = ffactor;
	metap->hashm_bsize = BufferGetPageSize(metabuf);
	/* find largest bitmap array size that will fit in page size */
	for (i = _hash_log2(metap->hashm_bsize); i > 0; --i)
	{
		if ((1 << i) <= (metap->hashm_bsize -
						 (MAXALIGN(sizeof(PageHeaderData)) +
						  MAXALIGN(sizeof(HashPageOpaqueData)))))
			break;
	}
	Assert(i > 0);
	metap->hashm_bmsize = 1 << i;
	metap->hashm_bmshift = i + BYTE_TO_BIT;
	Assert((1 << BMPG_SHIFT(metap)) == (BMPG_MASK(metap) + 1));

	metap->hashm_procid = index_getprocid(rel, 1, HASHPROC);

	/*
	 * We initialize the index with two buckets, 0 and 1, occupying physical
	 * blocks 1 and 2.  The first freespace bitmap page is in block 3.
	 */
	metap->hashm_maxbucket = metap->hashm_lowmask = 1;	/* nbuckets - 1 */
	metap->hashm_highmask = 3;	/* (nbuckets << 1) - 1 */

	MemSet((char *) metap->hashm_spares, 0, sizeof(metap->hashm_spares));
	MemSet((char *) metap->hashm_mapp, 0, sizeof(metap->hashm_mapp));

	metap->hashm_spares[1] = 1;	/* the first bitmap page is only spare */
	metap->hashm_ovflpoint = 1;
	metap->hashm_firstfree = 0;

	/*
	 * Initialize the first two buckets
	 */
	for (i = 0; i <= 1; i++)
	{
		buf = _hash_getbuf(rel, BUCKET_TO_BLKNO(metap, i), HASH_WRITE);
		pg = BufferGetPage(buf);
		_hash_pageinit(pg, BufferGetPageSize(buf));
		pageopaque = (HashPageOpaque) PageGetSpecialPointer(pg);
		pageopaque->hasho_prevblkno = InvalidBlockNumber;
//.........这里部分代码省略.........

/*
 * _hash_splitbucket -- split 'obucket' into 'obucket' and 'nbucket'
 *
 * We are splitting a bucket that consists of a base bucket page and zero
 * or more overflow (bucket chain) pages.  We must relocate tuples that
 * belong in the new bucket, and compress out any free space in the old
 * bucket.
 *
 * The caller must hold exclusive locks on both buckets to ensure that
 * no one else is trying to access them (see README).
 *
 * The caller must hold a pin, but no lock, on the metapage buffer.
 * The buffer is returned in the same state.  (The metapage is only
 * touched if it becomes necessary to add or remove overflow pages.)
 */
static void
_hash_splitbucket(Relation rel,
				  Buffer metabuf,
				  Bucket obucket,
				  Bucket nbucket,
				  BlockNumber start_oblkno,
				  BlockNumber start_nblkno,
				  uint32 maxbucket,
				  uint32 highmask,
				  uint32 lowmask)
{
	Bucket		bucket;
	Buffer		obuf;
	Buffer		nbuf;
	BlockNumber oblkno;
	BlockNumber nblkno;
	bool		null;
	Datum		datum;
	HashItem	hitem;
	HashPageOpaque oopaque;
	HashPageOpaque nopaque;
	IndexTuple	itup;
	Size		itemsz;
	OffsetNumber ooffnum;
	OffsetNumber noffnum;
	OffsetNumber omaxoffnum;
	Page		opage;
	Page		npage;
	TupleDesc	itupdesc = RelationGetDescr(rel);

	/*
	 * It should be okay to simultaneously write-lock pages from each
	 * bucket, since no one else can be trying to acquire buffer lock
	 * on pages of either bucket.
	 */
	oblkno = start_oblkno;
	nblkno = start_nblkno;
	obuf = _hash_getbuf(rel, oblkno, HASH_WRITE);
	nbuf = _hash_getbuf(rel, nblkno, HASH_WRITE);
	opage = BufferGetPage(obuf);
	npage = BufferGetPage(nbuf);

	_hash_checkpage(rel, opage, LH_BUCKET_PAGE);
	oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);

	/* initialize the new bucket's primary page */
	_hash_pageinit(npage, BufferGetPageSize(nbuf));
	nopaque = (HashPageOpaque) PageGetSpecialPointer(npage);
	nopaque->hasho_prevblkno = InvalidBlockNumber;
	nopaque->hasho_nextblkno = InvalidBlockNumber;
	nopaque->hasho_bucket = nbucket;
	nopaque->hasho_flag = LH_BUCKET_PAGE;
	nopaque->hasho_filler = HASHO_FILL;

	/*
	 * Partition the tuples in the old bucket between the old bucket and the
	 * new bucket, advancing along the old bucket's overflow bucket chain
	 * and adding overflow pages to the new bucket as needed.
	 */
	ooffnum = FirstOffsetNumber;
	omaxoffnum = PageGetMaxOffsetNumber(opage);
	for (;;)
	{
		/*
		 * at each iteration through this loop, each of these variables
		 * should be up-to-date: obuf opage oopaque ooffnum omaxoffnum
		 */

		/* check if we're at the end of the page */
		if (ooffnum > omaxoffnum)
		{
			/* at end of page, but check for an(other) overflow page */
			oblkno = oopaque->hasho_nextblkno;
			if (!BlockNumberIsValid(oblkno))
				break;
			/*
			 * we ran out of tuples on this particular page, but we
			 * have more overflow pages; advance to next page.
			 */
			_hash_wrtbuf(rel, obuf);

			obuf = _hash_getbuf(rel, oblkno, HASH_WRITE);
			opage = BufferGetPage(obuf);
			_hash_checkpage(rel, opage, LH_OVERFLOW_PAGE);
			oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);
//.........这里部分代码省略.........

static void
rtdoinsert(Relation r, IndexTuple itup, RTSTATE *rtstate)
{
	Page		page;
	Buffer		buffer;
	BlockNumber blk;
	IndexTuple	which;
	OffsetNumber l;
	RTSTACK    *stack;
	RTreePageOpaque opaque;
	Datum		datum;

	blk = P_ROOT;
	buffer = InvalidBuffer;
	stack = NULL;

	do
	{
		/* release the current buffer, read in the next one */
		buffer = ReleaseAndReadBuffer(buffer, r, blk);
		page = (Page) BufferGetPage(buffer);

		opaque = (RTreePageOpaque) PageGetSpecialPointer(page);
		if (!(opaque->flags & F_LEAF))
		{
			RTSTACK    *n;
			ItemId		iid;

			n = (RTSTACK *) palloc(sizeof(RTSTACK));
			n->rts_parent = stack;
			n->rts_blk = blk;
			n->rts_child = choose(r, page, itup, rtstate);
			stack = n;

			iid = PageGetItemId(page, n->rts_child);
			which = (IndexTuple) PageGetItem(page, iid);
			blk = ItemPointerGetBlockNumber(&(which->t_tid));
		}
	} while (!(opaque->flags & F_LEAF));

	if (nospace(page, itup))
	{
		/* need to do a split */
		rtdosplit(r, buffer, stack, itup, rtstate);
		freestack(stack);
		WriteBuffer(buffer);	/* don't forget to release buffer! */
		return;
	}

	/* add the item and write the buffer */
	if (PageIsEmpty(page))
	{
		l = PageAddItem(page, (Item) itup, IndexTupleSize(itup),
						FirstOffsetNumber,
						LP_USED);
	}
	else
	{
		l = PageAddItem(page, (Item) itup, IndexTupleSize(itup),
						OffsetNumberNext(PageGetMaxOffsetNumber(page)),
						LP_USED);
	}
	if (l == InvalidOffsetNumber)
		elog(ERROR, "failed to add index item to \"%s\"",
			 RelationGetRelationName(r));

	WriteBuffer(buffer);

	datum = IndexTupleGetDatum(itup);

	/* now expand the page boundary in the parent to include the new child */
	rttighten(r, stack, datum, IndexTupleAttSize(itup), rtstate);
	freestack(stack);
}

/*
 *	rtdosplit -- split a page in the tree.
 *
 *	  rtpicksplit does the interesting work of choosing the split.
 *	  This routine just does the bit-pushing.
 */
static void
rtdosplit(Relation r,
		  Buffer buffer,
		  RTSTACK *stack,
		  IndexTuple itup,
		  RTSTATE *rtstate)
{
	Page		p;
	Buffer		leftbuf,
				rightbuf;
	Page		left,
				right;
	ItemId		itemid;
	IndexTuple	item;
	IndexTuple	ltup,
				rtup;
	OffsetNumber maxoff;
	OffsetNumber i;
	OffsetNumber leftoff,
				rightoff;
	BlockNumber lbknum,
				rbknum;
	BlockNumber bufblock;
	RTreePageOpaque opaque;
	bool	   *isnull;
	SPLITVEC	v;
	OffsetNumber *spl_left,
			   *spl_right;
	TupleDesc	tupDesc;
	int			n;
	OffsetNumber newitemoff;

	p = (Page) BufferGetPage(buffer);
	opaque = (RTreePageOpaque) PageGetSpecialPointer(p);

	rtpicksplit(r, p, &v, itup, rtstate);

	/*
	 * The root of the tree is the first block in the relation.  If we're
	 * about to split the root, we need to do some hocus-pocus to enforce this
	 * guarantee.
	 */

	if (BufferGetBlockNumber(buffer) == P_ROOT)
	{
		leftbuf = ReadBuffer(r, P_NEW);
		RTInitBuffer(leftbuf, opaque->flags);
		lbknum = BufferGetBlockNumber(leftbuf);
		left = (Page) BufferGetPage(leftbuf);
	}
	else
	{
		leftbuf = buffer;
		IncrBufferRefCount(buffer);
		lbknum = BufferGetBlockNumber(buffer);
		left = (Page) PageGetTempPage(p, sizeof(RTreePageOpaqueData));
	}

	rightbuf = ReadBuffer(r, P_NEW);
	RTInitBuffer(rightbuf, opaque->flags);
	rbknum = BufferGetBlockNumber(rightbuf);
	right = (Page) BufferGetPage(rightbuf);

	spl_left = v.spl_left;
	spl_right = v.spl_right;
	leftoff = rightoff = FirstOffsetNumber;
	maxoff = PageGetMaxOffsetNumber(p);
	newitemoff = OffsetNumberNext(maxoff);

	/*
	 * spl_left contains a list of the offset numbers of the tuples that will
	 * go to the left page.  For each offset number, get the tuple item, then
	 * add the item to the left page.  Similarly for the right side.
	 */

	/* fill left node */
	for (n = 0; n < v.spl_nleft; n++)
	{
		i = *spl_left;
		if (i == newitemoff)
			item = itup;
		else
		{
			itemid = PageGetItemId(p, i);
			item = (IndexTuple) PageGetItem(p, itemid);
		}

		if (PageAddItem(left, (Item) item, IndexTupleSize(item),
						leftoff, LP_USED) == InvalidOffsetNumber)
			elog(ERROR, "failed to add index item to \"%s\"",
				 RelationGetRelationName(r));
		leftoff = OffsetNumberNext(leftoff);

		spl_left++;				/* advance in left split vector */
//.........这里部分代码省略.........

/*
 * replay delete operation of hash index
 */
static void
hash_xlog_delete(XLogReaderState *record)
{
	XLogRecPtr	lsn = record->EndRecPtr;
	xl_hash_delete *xldata = (xl_hash_delete *) XLogRecGetData(record);
	Buffer		bucketbuf = InvalidBuffer;
	Buffer		deletebuf;
	Page		page;
	XLogRedoAction action;

	/*
	 * Ensure we have a cleanup lock on primary bucket page before we start
	 * with the actual replay operation.  This is to ensure that neither a
	 * scan can start nor a scan can be already-in-progress during the replay
	 * of this operation.  If we allow scans during this operation, then they
	 * can miss some records or show the same record multiple times.
	 */
	if (xldata->is_primary_bucket_page)
		action = XLogReadBufferForRedoExtended(record, 1, RBM_NORMAL, true, &deletebuf);
	else
	{
		/*
		 * we don't care for return value as the purpose of reading bucketbuf
		 * is to ensure a cleanup lock on primary bucket page.
		 */
		(void) XLogReadBufferForRedoExtended(record, 0, RBM_NORMAL, true, &bucketbuf);

		action = XLogReadBufferForRedo(record, 1, &deletebuf);
	}

	/* replay the record for deleting entries in bucket page */
	if (action == BLK_NEEDS_REDO)
	{
		char	   *ptr;
		Size		len;

		ptr = XLogRecGetBlockData(record, 1, &len);

		page = (Page) BufferGetPage(deletebuf);

		if (len > 0)
		{
			OffsetNumber *unused;
			OffsetNumber *unend;

			unused = (OffsetNumber *) ptr;
			unend = (OffsetNumber *) ((char *) ptr + len);

			if ((unend - unused) > 0)
				PageIndexMultiDelete(page, unused, unend - unused);
		}

		/*
		 * Mark the page as not containing any LP_DEAD items only if
		 * clear_dead_marking flag is set to true. See comments in
		 * hashbucketcleanup() for details.
		 */
		if (xldata->clear_dead_marking)
		{
			HashPageOpaque pageopaque;

			pageopaque = (HashPageOpaque) PageGetSpecialPointer(page);
			pageopaque->hasho_flag &= ~LH_PAGE_HAS_DEAD_TUPLES;
		}

		PageSetLSN(page, lsn);
		MarkBufferDirty(deletebuf);
	}
	if (BufferIsValid(deletebuf))
		UnlockReleaseBuffer(deletebuf);

	if (BufferIsValid(bucketbuf))
		UnlockReleaseBuffer(bucketbuf);
}

/*
 * replay squeeze page operation of hash index
 */
static void
hash_xlog_squeeze_page(XLogReaderState *record)
{
	XLogRecPtr	lsn = record->EndRecPtr;
	xl_hash_squeeze_page *xldata = (xl_hash_squeeze_page *) XLogRecGetData(record);
	Buffer		bucketbuf = InvalidBuffer;
	Buffer		writebuf;
	Buffer		ovflbuf;
	Buffer		prevbuf = InvalidBuffer;
	Buffer		mapbuf;
	XLogRedoAction action;

	/*
	 * Ensure we have a cleanup lock on primary bucket page before we start
	 * with the actual replay operation.  This is to ensure that neither a
	 * scan can start nor a scan can be already-in-progress during the replay
	 * of this operation.  If we allow scans during this operation, then they
	 * can miss some records or show the same record multiple times.
	 */
	if (xldata->is_prim_bucket_same_wrt)
		action = XLogReadBufferForRedoExtended(record, 1, RBM_NORMAL, true, &writebuf);
	else
	{
		/*
		 * we don't care for return value as the purpose of reading bucketbuf
		 * is to ensure a cleanup lock on primary bucket page.
		 */
		(void) XLogReadBufferForRedoExtended(record, 0, RBM_NORMAL, true, &bucketbuf);

		action = XLogReadBufferForRedo(record, 1, &writebuf);
	}

	/* replay the record for adding entries in overflow buffer */
	if (action == BLK_NEEDS_REDO)
	{
		Page		writepage;
		char	   *begin;
		char	   *data;
		Size		datalen;
		uint16		ninserted = 0;

		data = begin = XLogRecGetBlockData(record, 1, &datalen);

		writepage = (Page) BufferGetPage(writebuf);

		if (xldata->ntups > 0)
		{
			OffsetNumber *towrite = (OffsetNumber *) data;

			data += sizeof(OffsetNumber) * xldata->ntups;

			while (data - begin < datalen)
			{
				IndexTuple	itup = (IndexTuple) data;
				Size		itemsz;
				OffsetNumber l;

				itemsz = IndexTupleDSize(*itup);
				itemsz = MAXALIGN(itemsz);

				data += itemsz;

				l = PageAddItem(writepage, (Item) itup, itemsz, towrite[ninserted], false, false);
				if (l == InvalidOffsetNumber)
					elog(ERROR, "hash_xlog_squeeze_page: failed to add item to hash index page, size %d bytes",
						 (int) itemsz);

				ninserted++;
			}
		}

		/*
		 * number of tuples inserted must be same as requested in REDO record.
		 */
		Assert(ninserted == xldata->ntups);

		/*
		 * if the page on which are adding tuples is a page previous to freed
		 * overflow page, then update its nextblno.
		 */
		if (xldata->is_prev_bucket_same_wrt)
		{
			HashPageOpaque writeopaque = (HashPageOpaque) PageGetSpecialPointer(writepage);

			writeopaque->hasho_nextblkno = xldata->nextblkno;
		}

		PageSetLSN(writepage, lsn);
		MarkBufferDirty(writebuf);
	}

	/* replay the record for initializing overflow buffer */
	if (XLogReadBufferForRedo(record, 2, &ovflbuf) == BLK_NEEDS_REDO)
	{
		Page		ovflpage;

		ovflpage = BufferGetPage(ovflbuf);
//.........这里部分代码省略.........

/*
 * replay allocation of page for split operation
 */
static void
hash_xlog_split_allocate_page(XLogReaderState *record)
{
	XLogRecPtr	lsn = record->EndRecPtr;
	xl_hash_split_allocate_page *xlrec = (xl_hash_split_allocate_page *) XLogRecGetData(record);
	Buffer		oldbuf;
	Buffer		newbuf;
	Buffer		metabuf;
	Size datalen PG_USED_FOR_ASSERTS_ONLY;
	char	   *data;
	XLogRedoAction action;

	/*
	 * To be consistent with normal operation, here we take cleanup locks on
	 * both the old and new buckets even though there can't be any concurrent
	 * inserts.
	 */

	/* replay the record for old bucket */
	action = XLogReadBufferForRedoExtended(record, 0, RBM_NORMAL, true, &oldbuf);

	/*
	 * Note that we still update the page even if it was restored from a full
	 * page image, because the special space is not included in the image.
	 */
	if (action == BLK_NEEDS_REDO || action == BLK_RESTORED)
	{
		Page		oldpage;
		HashPageOpaque oldopaque;

		oldpage = BufferGetPage(oldbuf);
		oldopaque = (HashPageOpaque) PageGetSpecialPointer(oldpage);

		oldopaque->hasho_flag = xlrec->old_bucket_flag;
		oldopaque->hasho_prevblkno = xlrec->new_bucket;

		PageSetLSN(oldpage, lsn);
		MarkBufferDirty(oldbuf);
	}

	/* replay the record for new bucket */
	newbuf = XLogInitBufferForRedo(record, 1);
	_hash_initbuf(newbuf, xlrec->new_bucket, xlrec->new_bucket,
				  xlrec->new_bucket_flag, true);
	if (!IsBufferCleanupOK(newbuf))
		elog(PANIC, "hash_xlog_split_allocate_page: failed to acquire cleanup lock");
	MarkBufferDirty(newbuf);
	PageSetLSN(BufferGetPage(newbuf), lsn);

	/*
	 * We can release the lock on old bucket early as well but doing here to
	 * consistent with normal operation.
	 */
	if (BufferIsValid(oldbuf))
		UnlockReleaseBuffer(oldbuf);
	if (BufferIsValid(newbuf))
		UnlockReleaseBuffer(newbuf);

	/*
	 * Note: in normal operation, we'd update the meta page while still
	 * holding lock on the old and new bucket pages.  But during replay it's
	 * not necessary to hold those locks, since no other bucket splits can be
	 * happening concurrently.
	 */

	/* replay the record for metapage changes */
	if (XLogReadBufferForRedo(record, 2, &metabuf) == BLK_NEEDS_REDO)
	{
		Page		page;
		HashMetaPage metap;

		page = BufferGetPage(metabuf);
		metap = HashPageGetMeta(page);
		metap->hashm_maxbucket = xlrec->new_bucket;

		data = XLogRecGetBlockData(record, 2, &datalen);

		if (xlrec->flags & XLH_SPLIT_META_UPDATE_MASKS)
		{
			uint32		lowmask;
			uint32	   *highmask;

			/* extract low and high masks. */
			memcpy(&lowmask, data, sizeof(uint32));
			highmask = (uint32 *) ((char *) data + sizeof(uint32));

			/* update metapage */
			metap->hashm_lowmask = lowmask;
			metap->hashm_highmask = *highmask;

			data += sizeof(uint32) * 2;
		}

		if (xlrec->flags & XLH_SPLIT_META_UPDATE_SPLITPOINT)
		{
			uint32		ovflpoint;
			uint32	   *ovflpages;
//.........这里部分代码省略.........

/*
 *	_hash_step() -- step to the next valid item in a scan in the bucket.
 *
 *		If no valid record exists in the requested direction, return
 *		false.	Else, return true and set the hashso_curpos for the
 *		scan to the right thing.
 *
 *		'bufP' points to the current buffer, which is pinned and read-locked.
 *		On success exit, we have pin and read-lock on whichever page
 *		contains the right item; on failure, we have released all buffers.
 */
bool
_hash_step(IndexScanDesc scan, Buffer *bufP, ScanDirection dir)
{
	Relation	rel = scan->indexRelation;
	HashScanOpaque so = (HashScanOpaque) scan->opaque;
	ItemPointer current;
	Buffer		buf;
	Page		page;
	HashPageOpaque opaque;
	OffsetNumber maxoff;
	OffsetNumber offnum;
	BlockNumber blkno;
	IndexTuple	itup;

	current = &(so->hashso_curpos);

	buf = *bufP;
	_hash_checkpage(rel, buf, LH_BUCKET_PAGE | LH_OVERFLOW_PAGE);
	page = BufferGetPage(buf);
	opaque = (HashPageOpaque) PageGetSpecialPointer(page);

	/*
	 * If _hash_step is called from _hash_first, current will not be valid, so
	 * we can't dereference it.  However, in that case, we presumably want to
	 * start at the beginning/end of the page...
	 */
	maxoff = PageGetMaxOffsetNumber(page);
	if (ItemPointerIsValid(current))
		offnum = ItemPointerGetOffsetNumber(current);
	else
		offnum = InvalidOffsetNumber;

	/*
	 * 'offnum' now points to the last tuple we examined (if any).
	 *
	 * continue to step through tuples until: 1) we get to the end of the
	 * bucket chain or 2) we find a valid tuple.
	 */
	do
	{
		switch (dir)
		{
			case ForwardScanDirection:
				if (offnum != InvalidOffsetNumber)
					offnum = OffsetNumberNext(offnum);	/* move forward */
				else
				{
					/* new page, locate starting position by binary search */
					offnum = _hash_binsearch(page, so->hashso_sk_hash);
				}

				for (;;)
				{
					/*
					 * check if we're still in the range of items with the
					 * target hash key
					 */
					if (offnum <= maxoff)
					{
						Assert(offnum >= FirstOffsetNumber);
						itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
						if (so->hashso_sk_hash == _hash_get_indextuple_hashkey(itup))
							break;		/* yes, so exit for-loop */
					}

					/*
					 * ran off the end of this page, try the next
					 */
					_hash_readnext(rel, &buf, &page, &opaque);
					if (BufferIsValid(buf))
					{
						maxoff = PageGetMaxOffsetNumber(page);
						offnum = _hash_binsearch(page, so->hashso_sk_hash);
					}
					else
					{
						/* end of bucket */
						itup = NULL;
						break;	/* exit for-loop */
					}
				}
				break;

			case BackwardScanDirection:
				if (offnum != InvalidOffsetNumber)
					offnum = OffsetNumberPrev(offnum);	/* move back */
				else
				{
					/* new page, locate starting position by binary search */
//.........这里部分代码省略.........

/*
 * btvacuumpage --- VACUUM one page
 *
 * This processes a single page for btvacuumscan().  In some cases we
 * must go back and re-examine previously-scanned pages; this routine
 * recurses when necessary to handle that case.
 *
 * blkno is the page to process.  orig_blkno is the highest block number
 * reached by the outer btvacuumscan loop (the same as blkno, unless we
 * are recursing to re-examine a previous page).
 */
static void
btvacuumpage(BTVacState *vstate, BlockNumber blkno, BlockNumber orig_blkno)
{
	IndexVacuumInfo *info = vstate->info;
	IndexBulkDeleteResult *stats = vstate->stats;
	IndexBulkDeleteCallback callback = vstate->callback;
	void	   *callback_state = vstate->callback_state;
	Relation	rel = info->index;
	bool		delete_now;
	BlockNumber recurse_to;
	Buffer		buf;
	Page		page;
	BTPageOpaque opaque;

restart:
	delete_now = false;
	recurse_to = P_NONE;

	/* call vacuum_delay_point while not holding any buffer lock */
	vacuum_delay_point();

	/*
	 * We can't use _bt_getbuf() here because it always applies
	 * _bt_checkpage(), which will barf on an all-zero page. We want to
	 * recycle all-zero pages, not fail.  Also, we want to use a nondefault
	 * buffer access strategy.
	 */
	buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL,
							 info->strategy);
	LockBuffer(buf, BT_READ);
	page = BufferGetPage(buf);
	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
	if (!PageIsNew(page))
		_bt_checkpage(rel, buf);

	/*
	 * If we are recursing, the only case we want to do anything with is a
	 * live leaf page having the current vacuum cycle ID.  Any other state
	 * implies we already saw the page (eg, deleted it as being empty).
	 */
	if (blkno != orig_blkno)
	{
		if (_bt_page_recyclable(page) ||
			P_IGNORE(opaque) ||
			!P_ISLEAF(opaque) ||
			opaque->btpo_cycleid != vstate->cycleid)
		{
			_bt_relbuf(rel, buf);
			return;
		}
	}

	/* If the page is in use, update lastUsedPage */
	if (!_bt_page_recyclable(page) && vstate->lastUsedPage < blkno)
		vstate->lastUsedPage = blkno;

	/* Page is valid, see what to do with it */
	if (_bt_page_recyclable(page))
	{
		/* Okay to recycle this page */
		RecordFreeIndexPage(rel, blkno);
		vstate->totFreePages++;
		stats->pages_deleted++;
	}
	else if (P_ISDELETED(opaque))
	{
		/* Already deleted, but can't recycle yet */
		stats->pages_deleted++;
	}
	else if (P_ISHALFDEAD(opaque))
	{
		/* Half-dead, try to delete */
		delete_now = true;
	}
	else if (P_ISLEAF(opaque))
	{
		OffsetNumber deletable[MaxOffsetNumber];
		int			ndeletable;
		OffsetNumber offnum,
					minoff,
					maxoff;

		/*
		 * Trade in the initial read lock for a super-exclusive write lock on
		 * this page.  We must get such a lock on every leaf page over the
		 * course of the vacuum scan, whether or not it actually contains any
		 * deletable tuples --- see nbtree/README.
		 */
		LockBuffer(buf, BUFFER_LOCK_UNLOCK);
//.........这里部分代码省略.........