C++ ItemPointerSet函数代码示例

/* ----------------------------------------------------------------
 *		tidin
 * ----------------------------------------------------------------
 */
Datum
tidin(PG_FUNCTION_ARGS)
{
	char	   *str = PG_GETARG_CSTRING(0);
	char	   *p,
			   *coord[NTIDARGS];
	int			i;
	ItemPointer result;
	BlockNumber blockNumber;
	OffsetNumber offsetNumber;
	char	   *badp;
	int			hold_offset;

	for (i = 0, p = str; *p && i < NTIDARGS && *p != RDELIM; p++)
		if (*p == DELIM || (*p == LDELIM && !i))
			coord[i++] = p + 1;

	if (i < NTIDARGS)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("invalid input syntax for type tid: \"%s\"",
						str)));

	errno = 0;
	blockNumber = strtoul(coord[0], &badp, 10);
	if (errno || *badp != DELIM)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("invalid input syntax for type tid: \"%s\"",
						str)));

	hold_offset = strtol(coord[1], &badp, 10);
	if (errno || *badp != RDELIM ||
		hold_offset > USHRT_MAX || hold_offset < 0)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("invalid input syntax for type tid: \"%s\"",
						str)));

	offsetNumber = hold_offset;

	result = (ItemPointer) palloc(sizeof(ItemPointerData));

	ItemPointerSet(result, blockNumber, offsetNumber);

	PG_RETURN_ITEMPOINTER(result);
}

/*
 *		tidrecv			- converts external binary format to tid
 */
Datum
tidrecv(PG_FUNCTION_ARGS)
{
	StringInfo	buf = (StringInfo) PG_GETARG_POINTER(0);
	ItemPointer result;
	BlockNumber blockNumber;
	OffsetNumber offsetNumber;

	blockNumber = pq_getmsgint(buf, sizeof(blockNumber));
	offsetNumber = pq_getmsgint(buf, sizeof(offsetNumber));

	result = (ItemPointer) palloc(sizeof(ItemPointerData));

	ItemPointerSet(result, blockNumber, offsetNumber);

	PG_RETURN_ITEMPOINTER(result);
}

/*
 * In the given revmap buffer (locked appropriately by caller), which is used
 * in a BRIN index of pagesPerRange pages per range, set the element
 * corresponding to heap block number heapBlk to the given TID.
 *
 * Once the operation is complete, the caller must update the LSN on the
 * returned buffer.
 *
 * This is used both in regular operation and during WAL replay.
 */
void
brinSetHeapBlockItemptr(Buffer buf, BlockNumber pagesPerRange,
						BlockNumber heapBlk, ItemPointerData tid)
{
	RevmapContents *contents;
	ItemPointerData *iptr;
	Page		page;

	/* The correct page should already be pinned and locked */
	page = BufferGetPage(buf);
	contents = (RevmapContents *) PageGetContents(page);
	iptr = (ItemPointerData *) contents->rm_tids;
	iptr += HEAPBLK_TO_REVMAP_INDEX(pagesPerRange, heapBlk);

	ItemPointerSet(iptr,
				   ItemPointerGetBlockNumber(&tid),
				   ItemPointerGetOffsetNumber(&tid));
}

/*
 * RelationPutHeapTuple - place tuple at specified page
 *
 * !!! EREPORT(ERROR) IS DISALLOWED HERE !!!  Must PANIC on failure!!!
 *
 * Note - caller must hold BUFFER_LOCK_EXCLUSIVE on the buffer.
 */
void
RelationPutHeapTuple(Relation relation,
					 Buffer buffer,
					 HeapTuple tuple,
					 bool token)
{
	Page		pageHeader;
	OffsetNumber offnum;

	/*
	 * A tuple that's being inserted speculatively should already have its
	 * token set.
	 */
	Assert(!token || HeapTupleHeaderIsSpeculative(tuple->t_data));

	/* Add the tuple to the page */
	pageHeader = BufferGetPage(buffer);

	offnum = PageAddItem(pageHeader, (Item) tuple->t_data,
						 tuple->t_len, InvalidOffsetNumber, false, true);

	if (offnum == InvalidOffsetNumber)
		elog(PANIC, "failed to add tuple to page");

	/* Update tuple->t_self to the actual position where it was stored */
	ItemPointerSet(&(tuple->t_self), BufferGetBlockNumber(buffer), offnum);

	/*
	 * Insert the correct position into CTID of the stored tuple, too (unless
	 * this is a speculative insertion, in which case the token is held in
	 * CTID field instead)
	 */
	if (!token)
	{
		ItemId		itemId = PageGetItemId(pageHeader, offnum);
		HeapTupleHeader item = (HeapTupleHeader) PageGetItem(pageHeader, itemId);

		item->t_ctid = tuple->t_self;
	}
}

/*
 * Construct a "dead" tuple to replace a tuple being deleted.
 *
 * The state can be SPGIST_REDIRECT, SPGIST_DEAD, or SPGIST_PLACEHOLDER.
 * For a REDIRECT tuple, a pointer (blkno+offset) must be supplied, and
 * the xid field is filled in automatically.
 *
 * This is called in critical sections, so we don't use palloc; the tuple
 * is built in preallocated storage.  It should be copied before another
 * call with different parameters can occur.
 */
SpGistDeadTuple
spgFormDeadTuple(SpGistState *state, int tupstate,
				 BlockNumber blkno, OffsetNumber offnum)
{
	SpGistDeadTuple tuple = (SpGistDeadTuple) state->deadTupleStorage;

	tuple->tupstate = tupstate;
	tuple->size = SGDTSIZE;
	tuple->nextOffset = InvalidOffsetNumber;

	if (tupstate == SPGIST_REDIRECT)
	{
		ItemPointerSet(&tuple->pointer, blkno, offnum);
		tuple->xid = state->myXid;
	}
	else
	{
		ItemPointerSetInvalid(&tuple->pointer);
		tuple->xid = InvalidTransactionId;
	}

	return tuple;
}

static ArrayTuple
vacuumSplitPage(GistVacuum *gv, Page tempPage, Buffer buffer, IndexTuple *addon, int curlenaddon)
{
	ArrayTuple	res = {NULL, 0, false};
	IndexTuple *vec;
	SplitedPageLayout *dist = NULL,
			   *ptr;
	int			i,
				veclen = 0;
	BlockNumber blkno = BufferGetBlockNumber(buffer);
	MemoryContext oldCtx = MemoryContextSwitchTo(gv->opCtx);

	vec = gistextractpage(tempPage, &veclen);
	vec = gistjoinvector(vec, &veclen, addon, curlenaddon);
	dist = gistSplit(gv->index, tempPage, vec, veclen, &(gv->giststate));

	MemoryContextSwitchTo(oldCtx);

	if (blkno != GIST_ROOT_BLKNO)
	{
		/* if non-root split then we should not allocate new buffer */
		dist->buffer = buffer;
		dist->page = tempPage;
		/* during vacuum we never split leaf page */
		GistPageGetOpaque(dist->page)->flags = 0;
	}
	else
		pfree(tempPage);

	res.itup = (IndexTuple *) palloc(sizeof(IndexTuple) * veclen);
	res.ituplen = 0;

	/* make new pages and fills them */
	for (ptr = dist; ptr; ptr = ptr->next)
	{
		char	   *data;

		if (ptr->buffer == InvalidBuffer)
		{
			ptr->buffer = gistNewBuffer(gv->index);
			GISTInitBuffer(ptr->buffer, 0);
			ptr->page = BufferGetPage(ptr->buffer);
		}
		ptr->block.blkno = BufferGetBlockNumber(ptr->buffer);

		data = (char *) (ptr->list);
		for (i = 0; i < ptr->block.num; i++)
		{
			if (PageAddItem(ptr->page, (Item) data, IndexTupleSize((IndexTuple) data), i + FirstOffsetNumber, false, false) == InvalidOffsetNumber)
				elog(ERROR, "failed to add item to index page in \"%s\"", RelationGetRelationName(gv->index));
			data += IndexTupleSize((IndexTuple) data);
		}

		ItemPointerSetBlockNumber(&(ptr->itup->t_tid), ptr->block.blkno);
		res.itup[res.ituplen] = (IndexTuple) palloc(IndexTupleSize(ptr->itup));
		memcpy(res.itup[res.ituplen], ptr->itup, IndexTupleSize(ptr->itup));
		res.ituplen++;
	}

	START_CRIT_SECTION();

	for (ptr = dist; ptr; ptr = ptr->next)
	{
		MarkBufferDirty(ptr->buffer);
		GistPageGetOpaque(ptr->page)->rightlink = InvalidBlockNumber;
	}

	/* restore splitted non-root page */
	if (blkno != GIST_ROOT_BLKNO)
	{
		PageRestoreTempPage(dist->page, BufferGetPage(dist->buffer));
		dist->page = BufferGetPage(dist->buffer);
	}

	if (!gv->index->rd_istemp)
	{
		XLogRecPtr	recptr;
		XLogRecData *rdata;
		ItemPointerData key;	/* set key for incomplete insert */
		char	   *xlinfo;

		ItemPointerSet(&key, blkno, TUPLE_IS_VALID);

		rdata = formSplitRdata(gv->index->rd_node, blkno,
							   false, &key, dist);
		xlinfo = rdata->data;

		recptr = XLogInsert(RM_GIST_ID, XLOG_GIST_PAGE_SPLIT, rdata);
		for (ptr = dist; ptr; ptr = ptr->next)
		{
			PageSetLSN(BufferGetPage(ptr->buffer), recptr);
			PageSetTLI(BufferGetPage(ptr->buffer), ThisTimeLineID);
		}

		pfree(xlinfo);
		pfree(rdata);
	}
	else
	{
		for (ptr = dist; ptr; ptr = ptr->next)
//.........这里部分代码省略.........

//.........这里部分代码省略.........
		 * Advance to next chain member.
		 */
		Assert(ItemPointerGetBlockNumber(&htup->t_ctid) ==
			   BufferGetBlockNumber(buffer));
		offnum = ItemPointerGetOffsetNumber(&htup->t_ctid);
		priorXmax = HeapTupleHeaderGetXmax(htup);
	}

	/*
	 * If we found a DEAD tuple in the chain, adjust the HOT chain so that all
	 * the DEAD tuples at the start of the chain are removed and the root line
	 * pointer is appropriately redirected.
	 */
	if (OffsetNumberIsValid(latestdead))
	{
		/*
		 * Mark as unused each intermediate item that we are able to remove
		 * from the chain.
		 *
		 * When the previous item is the last dead tuple seen, we are at the
		 * right candidate for redirection.
		 */
		for (i = 1; (i < nchain) && (chainitems[i - 1] != latestdead); i++)
		{
			heap_prune_record_unused(prstate, chainitems[i]);
			ndeleted++;
		}

		/*
		 * If the root entry had been a normal tuple, we are deleting it, so
		 * count it in the result.	But changing a redirect (even to DEAD
		 * state) doesn't count.
		 */
		if (ItemIdIsNormal(rootlp))
			ndeleted++;

		/*
		 * If the DEAD tuple is at the end of the chain, the entire chain is
		 * dead and the root line pointer can be marked dead.  Otherwise just
		 * redirect the root to the correct chain member.
		 */
		if (i >= nchain)
			heap_prune_record_dead(prstate, rootoffnum);
		else
		{
			heap_prune_record_redirect(prstate, rootoffnum, chainitems[i]);
			/* If the redirection will be a move, need more processing */
			if (redirect_move)
				redirect_target = chainitems[i];
		}
	}
	else if (nchain < 2 && ItemIdIsRedirected(rootlp))
	{
		/*
		 * We found a redirect item that doesn't point to a valid follow-on
		 * item.  This can happen if the loop in heap_page_prune caused us to
		 * visit the dead successor of a redirect item before visiting the
		 * redirect item.  We can clean up by setting the redirect item to
		 * DEAD state.
		 */
		heap_prune_record_dead(prstate, rootoffnum);
	}
	else if (redirect_move && ItemIdIsRedirected(rootlp))
	{
		/*
		 * If we desire to eliminate LP_REDIRECT items by moving tuples, make
		 * a redirection entry for each redirected root item; this will cause
		 * heap_page_prune_execute to actually do the move. (We get here only
		 * when there are no DEAD tuples in the chain; otherwise the
		 * redirection entry was made above.)
		 */
		heap_prune_record_redirect(prstate, rootoffnum, chainitems[1]);
		redirect_target = chainitems[1];
	}

	/*
	 * If we are going to implement a redirect by moving tuples, we have to
	 * issue a cache invalidation against the redirection target tuple,
	 * because its CTID will be effectively changed by the move.  Note that
	 * CacheInvalidateHeapTuple only queues the request, it doesn't send it;
	 * if we fail before reaching EndNonTransactionalInvalidation, nothing
	 * happens and no harm is done.
	 */
	if (OffsetNumberIsValid(redirect_target))
	{
		ItemId		firstlp = PageGetItemId(dp, redirect_target);
		HeapTupleData firsttup;

		Assert(ItemIdIsNormal(firstlp));
		/* Set up firsttup to reference the tuple at its existing CTID */
		firsttup.t_data = (HeapTupleHeader) PageGetItem(dp, firstlp);
		firsttup.t_len = ItemIdGetLength(firstlp);
		ItemPointerSet(&firsttup.t_self,
					   BufferGetBlockNumber(buffer),
					   redirect_target);
		CacheInvalidateHeapTuple(relation, &firsttup);
	}

	return ndeleted;
}

//.........这里部分代码省略.........
	 * Check page is still empty etc, else abandon deletion.  The empty check
	 * is necessary since someone else might have inserted into it while we
	 * didn't have it locked; the others are just for paranoia's sake.
	 */
	if (P_RIGHTMOST(opaque) || P_ISROOT(opaque) || P_ISDELETED(opaque) ||
		P_FIRSTDATAKEY(opaque) <= PageGetMaxOffsetNumber(page))
	{
		_bt_relbuf(rel, buf);
		if (BufferIsValid(lbuf))
			_bt_relbuf(rel, lbuf);
		return 0;
	}
	if (opaque->btpo_prev != leftsib)
		elog(ERROR, "left link changed unexpectedly in block %u of index \"%s\"",
			 target, RelationGetRelationName(rel));

	/*
	 * And next write-lock the (current) right sibling.
	 */
	rightsib = opaque->btpo_next;
	rbuf = _bt_getbuf(rel, rightsib, BT_WRITE);
	page = BufferGetPage(rbuf);
	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
	if (opaque->btpo_prev != target)
		elog(ERROR, "right sibling's left-link doesn't match: "
			 "block %u links to %u instead of expected %u in index \"%s\"",
			 rightsib, opaque->btpo_prev, target,
			 RelationGetRelationName(rel));

	/*
	 * Next find and write-lock the current parent of the target page. This is
	 * essentially the same as the corresponding step of splitting.
	 */
	ItemPointerSet(&(stack->bts_btentry.t_tid), target, P_HIKEY);
	pbuf = _bt_getstackbuf(rel, stack, BT_WRITE);
	if (pbuf == InvalidBuffer)
		elog(ERROR, "failed to re-find parent key in index \"%s\" for deletion target page %u",
			 RelationGetRelationName(rel), target);
	parent = stack->bts_blkno;
	poffset = stack->bts_offset;

	/*
	 * If the target is the rightmost child of its parent, then we can't
	 * delete, unless it's also the only child --- in which case the parent
	 * changes to half-dead status.  The "can't delete" case should have been
	 * detected by _bt_parent_deletion_safe, so complain if we see it now.
	 */
	page = BufferGetPage(pbuf);
	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
	maxoff = PageGetMaxOffsetNumber(page);
	parent_half_dead = false;
	parent_one_child = false;
	if (poffset >= maxoff)
	{
		if (poffset == P_FIRSTDATAKEY(opaque))
			parent_half_dead = true;
		else
			elog(ERROR, "failed to delete rightmost child %u of block %u in index \"%s\"",
				 target, parent, RelationGetRelationName(rel));
	}
	else
	{
		/* Will there be exactly one child left in this parent? */
		if (OffsetNumberNext(P_FIRSTDATAKEY(opaque)) == maxoff)
			parent_one_child = true;
	}

//.........这里部分代码省略.........
		 * start over.
		 */
		LockBuffer(oldbuf, BUFFER_LOCK_UNLOCK);
		return false;
	}
	else
	{
		/*
		 * Not enough free space on the oldpage. Put the new tuple on the new
		 * page, and update the revmap.
		 */
		Page		newpage = BufferGetPage(newbuf);
		Buffer		revmapbuf;
		ItemPointerData newtid;
		OffsetNumber newoff;
		BlockNumber newblk = InvalidBlockNumber;
		Size		freespace = 0;

		revmapbuf = brinLockRevmapPageForUpdate(revmap, heapBlk);

		START_CRIT_SECTION();

		/*
		 * We need to initialize the page if it's newly obtained.  Note we
		 * will WAL-log the initialization as part of the update, so we don't
		 * need to do that here.
		 */
		if (extended)
			brin_page_init(BufferGetPage(newbuf), BRIN_PAGETYPE_REGULAR);

		PageIndexTupleDeleteNoCompact(oldpage, oldoff);
		newoff = PageAddItem(newpage, (Item) newtup, newsz,
							 InvalidOffsetNumber, false, false);
		if (newoff == InvalidOffsetNumber)
			elog(ERROR, "failed to add BRIN tuple to new page");
		MarkBufferDirty(oldbuf);
		MarkBufferDirty(newbuf);

		/* needed to update FSM below */
		if (extended)
		{
			newblk = BufferGetBlockNumber(newbuf);
			freespace = br_page_get_freespace(newpage);
		}

		ItemPointerSet(&newtid, BufferGetBlockNumber(newbuf), newoff);
		brinSetHeapBlockItemptr(revmapbuf, pagesPerRange, heapBlk, newtid);
		MarkBufferDirty(revmapbuf);

		/* XLOG stuff */
		if (RelationNeedsWAL(idxrel))
		{
			xl_brin_update xlrec;
			XLogRecPtr	recptr;
			uint8		info;

			info = XLOG_BRIN_UPDATE | (extended ? XLOG_BRIN_INIT_PAGE : 0);

			xlrec.insert.offnum = newoff;
			xlrec.insert.heapBlk = heapBlk;
			xlrec.insert.pagesPerRange = pagesPerRange;
			xlrec.oldOffnum = oldoff;

			XLogBeginInsert();

			/* new page */
			XLogRegisterData((char *) &xlrec, SizeOfBrinUpdate);

			XLogRegisterBuffer(0, newbuf, REGBUF_STANDARD | (extended ? REGBUF_WILL_INIT : 0));
			XLogRegisterBufData(0, (char *) newtup, newsz);

			/* revmap page */
			XLogRegisterBuffer(1, revmapbuf, 0);

			/* old page */
			XLogRegisterBuffer(2, oldbuf, REGBUF_STANDARD);

			recptr = XLogInsert(RM_BRIN_ID, info);

			PageSetLSN(oldpage, recptr);
			PageSetLSN(newpage, recptr);
			PageSetLSN(BufferGetPage(revmapbuf), recptr);
		}

		END_CRIT_SECTION();

		LockBuffer(revmapbuf, BUFFER_LOCK_UNLOCK);
		LockBuffer(oldbuf, BUFFER_LOCK_UNLOCK);
		UnlockReleaseBuffer(newbuf);

		if (extended)
		{
			Assert(BlockNumberIsValid(newblk));
			RecordPageWithFreeSpace(idxrel, newblk, freespace);
			FreeSpaceMapVacuum(idxrel);
		}

		return true;
	}
}

/*
 *	_bt_step() -- Step one item in the requested direction in a scan on
 *				  the tree.
 *
 *		*bufP is the current buffer (read-locked and pinned).  If we change
 *		pages, it's updated appropriately.
 *
 *		If successful, update scan's currentItemData and return true.
 *		If no adjacent record exists in the requested direction,
 *		release buffer pin/locks and return false.
 */
bool
_bt_step(IndexScanDesc scan, Buffer *bufP, ScanDirection dir)
{
	Relation	rel = scan->indexRelation;
	ItemPointer current = &(scan->currentItemData);
	BTScanOpaque so = (BTScanOpaque) scan->opaque;
	Page		page;
	BTPageOpaque opaque;
	OffsetNumber offnum,
				maxoff;
	BlockNumber blkno;

	/*
	 * Don't use ItemPointerGetOffsetNumber or you risk to get assertion
	 * due to ability of ip_posid to be equal 0.
	 */
	offnum = current->ip_posid;

	page = BufferGetPage(*bufP);
	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
	maxoff = PageGetMaxOffsetNumber(page);

	if (ScanDirectionIsForward(dir))
	{
		if (!PageIsEmpty(page) && offnum < maxoff)
			offnum = OffsetNumberNext(offnum);
		else
		{
			/* Walk right to the next page with data */
			for (;;)
			{
				/* if we're at end of scan, release the buffer and return */
				if (P_RIGHTMOST(opaque))
				{
					_bt_relbuf(rel, *bufP);
					ItemPointerSetInvalid(current);
					*bufP = so->btso_curbuf = InvalidBuffer;
					return false;
				}
				/* step right one page */
				blkno = opaque->btpo_next;
				_bt_relbuf(rel, *bufP);
				*bufP = _bt_getbuf(rel, blkno, BT_READ);
				page = BufferGetPage(*bufP);
				opaque = (BTPageOpaque) PageGetSpecialPointer(page);
				if (!P_IGNORE(opaque))
				{
					maxoff = PageGetMaxOffsetNumber(page);
					/* done if it's not empty */
					offnum = P_FIRSTDATAKEY(opaque);
					if (!PageIsEmpty(page) && offnum <= maxoff)
						break;
				}
			}
		}
	}
	else
/* backwards scan */
	{
		if (offnum > P_FIRSTDATAKEY(opaque))
			offnum = OffsetNumberPrev(offnum);
		else
		{
			/*
			 * Walk left to the next page with data.  This is much more
			 * complex than the walk-right case because of the possibility
			 * that the page to our left splits while we are in flight to
			 * it, plus the possibility that the page we were on gets
			 * deleted after we leave it.  See nbtree/README for details.
			 */
			for (;;)
			{
				*bufP = _bt_walk_left(rel, *bufP);

				/* if we're at end of scan, return failure */
				if (*bufP == InvalidBuffer)
				{
					ItemPointerSetInvalid(current);
					so->btso_curbuf = InvalidBuffer;
					return false;
				}
				page = BufferGetPage(*bufP);
				opaque = (BTPageOpaque) PageGetSpecialPointer(page);

				/*
				 * Okay, we managed to move left to a non-deleted page.
				 * Done if it's not half-dead and not empty.  Else loop
				 * back and do it all again.
				 */
//.........这里部分代码省略.........

/*
 * Finish writing out the completed btree.
 */
static void
_bt_uppershutdown(BTWriteState *wstate, BTPageState *state)
{
	BTPageState *s;
	BlockNumber rootblkno = P_NONE;
	uint32		rootlevel = 0;
	Page		metapage;

	/*
	 * Each iteration of this loop completes one more level of the tree.
	 */
	for (s = state; s != NULL; s = s->btps_next)
	{
		BlockNumber blkno;
		BTPageOpaque opaque;

		blkno = s->btps_blkno;
		opaque = (BTPageOpaque) PageGetSpecialPointer(s->btps_page);

		/*
		 * We have to link the last page on this level to somewhere.
		 *
		 * If we're at the top, it's the root, so attach it to the metapage.
		 * Otherwise, add an entry for it to its parent using its minimum key.
		 * This may cause the last page of the parent level to split, but
		 * that's not a problem -- we haven't gotten to it yet.
		 */
		if (s->btps_next == NULL)
		{
			opaque->btpo_flags |= BTP_ROOT;
			rootblkno = blkno;
			rootlevel = s->btps_level;
		}
		else
		{
			Assert(s->btps_minkey != NULL);
			ItemPointerSet(&(s->btps_minkey->t_tid), blkno, P_HIKEY);
			_bt_buildadd(wstate, s->btps_next, s->btps_minkey);
			pfree(s->btps_minkey);
			s->btps_minkey = NULL;
		}

		/*
		 * This is the rightmost page, so the ItemId array needs to be slid
		 * back one slot.  Then we can dump out the page.
		 */
		_bt_slideleft(s->btps_page);
		_bt_blwritepage(wstate, s->btps_page, s->btps_blkno);
		s->btps_page = NULL;	/* writepage freed the workspace */
	}

	/*
	 * As the last step in the process, construct the metapage and make it
	 * point to the new root (unless we had no data at all, in which case it's
	 * set to point to "P_NONE").  This changes the index to the "valid" state
	 * by filling in a valid magic number in the metapage.
	 */
	metapage = (Page) palloc(BLCKSZ);
	_bt_initmetapage(metapage, rootblkno, rootlevel);
	_bt_blwritepage(wstate, metapage, BTREE_METAPAGE);
}

//.........这里部分代码省略.........
	 */
	if (state->rs_new_rel->rd_rel->relkind == RELKIND_TOASTVALUE)
	{
		/* toast table entries should never be recursively toasted */
		Assert(!HeapTupleHasExternal(tup));
		heaptup = tup;
	}
	else if (HeapTupleHasExternal(tup) || tup->t_len > TOAST_TUPLE_THRESHOLD)
		heaptup = toast_insert_or_update(state->rs_new_rel, tup, NULL,
										 HEAP_INSERT_SKIP_FSM |
										 (state->rs_use_wal ?
										  0 : HEAP_INSERT_SKIP_WAL));
	else
		heaptup = tup;

	len = MAXALIGN(heaptup->t_len);		/* be conservative */

	/*
	 * If we're gonna fail for oversize tuple, do it right away
	 */
	if (len > MaxHeapTupleSize)
		ereport(ERROR,
				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
				 errmsg("row is too big: size %zu, maximum size %zu",
						len, MaxHeapTupleSize)));

	/* Compute desired extra freespace due to fillfactor option */
	saveFreeSpace = RelationGetTargetPageFreeSpace(state->rs_new_rel,
												   HEAP_DEFAULT_FILLFACTOR);

	/* Now we can check to see if there's enough free space already. */
	if (state->rs_buffer_valid)
	{
		pageFreeSpace = PageGetHeapFreeSpace(page);

		if (len + saveFreeSpace > pageFreeSpace)
		{
			/* Doesn't fit, so write out the existing page */

			/* XLOG stuff */
			if (state->rs_use_wal)
				log_newpage(&state->rs_new_rel->rd_node,
							MAIN_FORKNUM,
							state->rs_blockno,
							page,
							true);

			/*
			 * Now write the page. We say isTemp = true even if it's not a
			 * temp table, because there's no need for smgr to schedule an
			 * fsync for this write; we'll do it ourselves in
			 * end_heap_rewrite.
			 */
			RelationOpenSmgr(state->rs_new_rel);

			PageSetChecksumInplace(page, state->rs_blockno);

			smgrextend(state->rs_new_rel->rd_smgr, MAIN_FORKNUM,
					   state->rs_blockno, (char *) page, true);

			state->rs_blockno++;
			state->rs_buffer_valid = false;
		}
	}

	if (!state->rs_buffer_valid)
	{
		/* Initialize a new empty page */
		PageInit(page, BLCKSZ, 0);
		state->rs_buffer_valid = true;
	}

	/* And now we can insert the tuple into the page */
	newoff = PageAddItem(page, (Item) heaptup->t_data, heaptup->t_len,
						 InvalidOffsetNumber, false, true);
	if (newoff == InvalidOffsetNumber)
		elog(ERROR, "failed to add tuple");

	/* Update caller's t_self to the actual position where it was stored */
	ItemPointerSet(&(tup->t_self), state->rs_blockno, newoff);

	/*
	 * Insert the correct position into CTID of the stored tuple, too, if the
	 * caller didn't supply a valid CTID.
	 */
	if (!ItemPointerIsValid(&tup->t_data->t_ctid))
	{
		ItemId		newitemid;
		HeapTupleHeader onpage_tup;

		newitemid = PageGetItemId(page, newoff);
		onpage_tup = (HeapTupleHeader) PageGetItem(page, newitemid);

		onpage_tup->t_ctid = tup->t_self;
	}

	/* If heaptup is a private copy, release it. */
	if (heaptup != tup)
		heap_freetuple(heaptup);
}

/*
 *	_bt_endpoint() -- Find the first or last key in the index.
 *
 * This is used by _bt_first() to set up a scan when we've determined
 * that the scan must start at the beginning or end of the index (for
 * a forward or backward scan respectively).
 */
static bool
_bt_endpoint(IndexScanDesc scan, ScanDirection dir)
{
	Relation	rel;
	Buffer		buf;
	Page		page;
	BTPageOpaque opaque;
	ItemPointer current;
	OffsetNumber maxoff;
	OffsetNumber start;
	BlockNumber blkno;
	BTItem		btitem;
	IndexTuple	itup;
	BTScanOpaque so;
	bool		res;
	bool		continuescan;

	rel = scan->indexRelation;
	current = &(scan->currentItemData);
	so = (BTScanOpaque) scan->opaque;

	/*
	 * Scan down to the leftmost or rightmost leaf page.  This is a
	 * simplified version of _bt_search().	We don't maintain a stack
	 * since we know we won't need it.
	 */
	buf = _bt_get_endpoint(rel, 0, ScanDirectionIsBackward(dir));

	if (!BufferIsValid(buf))
	{
		/* empty index... */
		ItemPointerSetInvalid(current);
		so->btso_curbuf = InvalidBuffer;
		return false;
	}

	blkno = BufferGetBlockNumber(buf);
	page = BufferGetPage(buf);
	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
	Assert(P_ISLEAF(opaque));

	maxoff = PageGetMaxOffsetNumber(page);

	if (ScanDirectionIsForward(dir))
	{
		/* There could be dead pages to the left, so not this: */
		/* Assert(P_LEFTMOST(opaque)); */

		start = P_FIRSTDATAKEY(opaque);
	}
	else if (ScanDirectionIsBackward(dir))
	{
		Assert(P_RIGHTMOST(opaque));

		start = PageGetMaxOffsetNumber(page);
		if (start < P_FIRSTDATAKEY(opaque))		/* watch out for empty
												 * page */
			start = P_FIRSTDATAKEY(opaque);
	}
	else
	{
		elog(ERROR, "invalid scan direction: %d", (int) dir);
		start = 0;				/* keep compiler quiet */
	}

	ItemPointerSet(current, blkno, start);
	/* remember which buffer we have pinned */
	so->btso_curbuf = buf;

	/*
	 * Left/rightmost page could be empty due to deletions, if so step
	 * till we find a nonempty page.
	 */
	if (start > maxoff)
	{
		if (!_bt_step(scan, &buf, dir))
			return false;
		start = ItemPointerGetOffsetNumber(current);
		page = BufferGetPage(buf);
	}

	btitem = (BTItem) PageGetItem(page, PageGetItemId(page, start));
	itup = &(btitem->bti_itup);

	/* see if we picked a winner */
	if (_bt_checkkeys(scan, itup, dir, &continuescan))
	{
		/* yes, return it */
		scan->xs_ctup.t_self = itup->t_tid;
		res = true;
	}
	else if (continuescan)
	{
//.........这里部分代码省略.........

//.........这里部分代码省略.........
		funcctx->user_fctx = (void *) info;

		info->outattnum = outattnum;
		info->ireloid = irelid;

		hrel = relation_open(irel->rd_index->indrelid, AccessShareLock);
		if (hrel->rd_rel != NULL &&
			(hrel->rd_rel->relstorage == 'a' ||
			 hrel->rd_rel->relstorage == 'c'))
		{
			relation_close(hrel, AccessShareLock);
			hrel = NULL;
			info->hreloid = InvalidOid;
		}
		else
			info->hreloid = irel->rd_index->indrelid;
		info->num_pages = RelationGetNumberOfBlocks(irel);
		info->blkno = BTREE_METAPAGE + 1;
		info->page = NULL;

		MemoryContextSwitchTo(oldcontext);
	}

	funcctx = SRF_PERCALL_SETUP();
	info = (readindexinfo *) funcctx->user_fctx;

	/*
	 * Open the relations (on first call, we did that above already).
	 * We unfortunately have to look up the relcache entry on every call,
	 * because if we store it in the cross-call context, we won't get a
	 * chance to release it if the function isn't run to completion,
	 * e.g. because of a LIMIT clause. We only lock the relation on the
	 * first call, and keep the lock until completion, however.
	 */
	if (!irel)
		irel = index_open(info->ireloid, NoLock);
	if (!hrel && info->hreloid != InvalidOid)
		hrel = heap_open(info->hreloid, NoLock);

	while (info->blkno < info->num_pages)
	{
		Datum		values[255];
		bool		nulls[255];
		ItemPointerData		itid;
		HeapTuple	tuple;
		Datum		result;

		if (info->page == NULL)
		{
			Buffer		buf;

			/*
			 * Make copy of the page, because we cannot hold a buffer pin
			 * across calls (we wouldn't have a chance to release it, if the
			 * function isn't run to completion.)
			 */
			info->page = palloc(BLCKSZ);

			MIRROREDLOCK_BUFMGR_LOCK;
			buf = ReadBuffer(irel, info->blkno);
			memcpy(info->page, BufferGetPage(buf), BLCKSZ);
			ReleaseBuffer(buf);
			MIRROREDLOCK_BUFMGR_UNLOCK;

			info->opaque = (BTPageOpaque) PageGetSpecialPointer(info->page);
			info->minoff = P_FIRSTDATAKEY(info->opaque);
			info->maxoff = PageGetMaxOffsetNumber(info->page);
			info->offnum = info->minoff;
		}
		if (!P_ISLEAF(info->opaque) || info->offnum > info->maxoff)
		{
			pfree(info->page);
			info->page = NULL;
			info->blkno++;
			continue;
		}

		MemSet(nulls, false, info->outattnum * sizeof(bool));

		ItemPointerSet(&itid, info->blkno, info->offnum);
		values[0] = ItemPointerGetDatum(&itid);
		readindextuple(info, irel, hrel, values, nulls);

		info->offnum = OffsetNumberNext(info->offnum);

		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
		result = HeapTupleGetDatum(tuple);

		if (hrel != NULL)
			heap_close(hrel, NoLock);
		index_close(irel, NoLock);

		SRF_RETURN_NEXT(funcctx, result);
	}

	if (hrel != NULL)
		heap_close(hrel, AccessShareLock);
	index_close(irel, AccessShareLock);
	SRF_RETURN_DONE(funcctx);
}

//.........这里部分代码省略.........
		tups_vacuumed += heap_page_prune(onerel, buf, OldestXmin,
										 false, false);

		/*
		 * Now scan the page to collect vacuumable items and check for tuples
		 * requiring freezing.
		 */
		nfrozen = 0;
		hastup = false;
		prev_dead_count = vacrelstats->num_dead_tuples;
		maxoff = PageGetMaxOffsetNumber(page);
		for (offnum = FirstOffsetNumber;
			 offnum <= maxoff;
			 offnum = OffsetNumberNext(offnum))
		{
			ItemId		itemid;

			itemid = PageGetItemId(page, offnum);

			/* Unused items require no processing, but we count 'em */
			if (!ItemIdIsUsed(itemid))
			{
				nunused += 1;
				continue;
			}

			/* Redirect items mustn't be touched */
			if (ItemIdIsRedirected(itemid))
			{
				hastup = true;	/* this page won't be truncatable */
				continue;
			}

			ItemPointerSet(&(tuple.t_self), blkno, offnum);

			/*
			 * DEAD item pointers are to be vacuumed normally; but we don't
			 * count them in tups_vacuumed, else we'd be double-counting (at
			 * least in the common case where heap_page_prune() just freed up
			 * a non-HOT tuple).
			 */
			if (ItemIdIsDead(itemid))
			{
				lazy_record_dead_tuple(vacrelstats, &(tuple.t_self));
				continue;
			}

			Assert(ItemIdIsNormal(itemid));

			tuple.t_data = (HeapTupleHeader) PageGetItem(page, itemid);
			tuple.t_len = ItemIdGetLength(itemid);

			tupgone = false;

			switch (HeapTupleSatisfiesVacuum(onerel, tuple.t_data, OldestXmin, buf))
			{
				case HEAPTUPLE_DEAD:

					/*
					 * Ordinarily, DEAD tuples would have been removed by
					 * heap_page_prune(), but it's possible that the tuple
					 * state changed since heap_page_prune() looked.  In
					 * particular an INSERT_IN_PROGRESS tuple could have
					 * changed to DEAD if the inserter aborted.  So this
					 * cannot be considered an error condition.
					 *