C++ PageGetFreeSpace函数代码示例

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;
}

/*
 * Release resources associated with a BrinBuildState.
 */
static void
terminate_brin_buildstate(BrinBuildState *state)
{
	/*
	 * Release the last index buffer used.  We might as well ensure that
	 * whatever free space remains in that page is available in FSM, too.
	 */
	if (!BufferIsInvalid(state->bs_currentInsertBuf))
	{
		Page		page;
		Size		freespace;
		BlockNumber blk;

		page = BufferGetPage(state->bs_currentInsertBuf);
		freespace = PageGetFreeSpace(page);
		blk = BufferGetBlockNumber(state->bs_currentInsertBuf);
		ReleaseBuffer(state->bs_currentInsertBuf);
		RecordPageWithFreeSpace(state->bs_irel, blk, freespace);
		FreeSpaceMapVacuumRange(state->bs_irel, blk, blk + 1);
	}

	brin_free_desc(state->bs_bdesc);
	pfree(state->bs_dtuple);
	pfree(state);
}

/*
 * Return the amount of free space on a regular BRIN index page.
 *
 * If the page is not a regular page, or has been marked with the
 * BRIN_EVACUATE_PAGE flag, returns 0.
 */
static Size
br_page_get_freespace(Page page)
{
	if (!BRIN_IS_REGULAR_PAGE(page) ||
		(BrinPageFlags(page) & BRIN_EVACUATE_PAGE) != 0)
		return 0;
	else
		return PageGetFreeSpace(page);
}

/*
 * 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);
}

/*
 * Return the amount of free space on a regular BRIN index page.
 *
 * If the page is not a regular page, or has been marked with the
 * BRIN_EVACUATE_PAGE flag, returns 0.
 */
static Size
br_page_get_freespace(Page page)
{
	BrinSpecialSpace *special;

	special = (BrinSpecialSpace *) PageGetSpecialPointer(page);
	if (!BRIN_IS_REGULAR_PAGE(page) ||
		(special->flags & BRIN_EVACUATE_PAGE) != 0)
		return 0;
	else
		return PageGetFreeSpace(page);
}

/*
 * PageGetHeapFreeSpace
 *		Returns the size of the free (allocatable) space on a page,
 *		reduced by the space needed for a new line pointer.
 *
 * The difference between this and PageGetFreeSpace is that this will return
 * zero if there are already MaxHeapTuplesPerPage line pointers in the page
 * and none are free.  We use this to enforce that no more than
 * MaxHeapTuplesPerPage line pointers are created on a heap page.  (Although
 * no more tuples than that could fit anyway, in the presence of redirected
 * or dead line pointers it'd be possible to have too many line pointers.
 * To avoid breaking code that assumes MaxHeapTuplesPerPage is a hard limit
 * on the number of line pointers, we make this extra check.)
 */
Size
PageGetHeapFreeSpace(Page page)
{
	Size		space;

	space = PageGetFreeSpace(page);
	if (space > 0)
	{
		OffsetNumber offnum,
					nline;

		/*
		 * Are there already MaxHeapTuplesPerPage line pointers in the page?
		 */
		nline = PageGetMaxOffsetNumber(page);
		if (nline >= MaxHeapTuplesPerPage)
		{
			if (PageHasFreeLinePointers((PageHeader) page))
			{
				/*
				 * Since this is just a hint, we must confirm that there is
				 * indeed a free line pointer
				 */
				for (offnum = FirstOffsetNumber; offnum <= nline; offnum = OffsetNumberNext(offnum))
				{
					ItemId		lp = PageGetItemId(page, offnum);

					if (!ItemIdIsUsed(lp))
						break;
				}

				if (offnum > nline)
				{
					/*
					 * The hint is wrong, but we can't clear it here since we
					 * don't have the ability to mark the page dirty.
					 */
					space = 0;
				}
			}
			else
			{
				/*
				 * Although the hint might be wrong, PageAddItem will believe
				 * it anyway, so we must believe it too.
				 */
				space = 0;
			}
		}
	}
	return space;
}

/*
 *	lazy_vacuum_heap() -- second pass over the heap
 *
 *		This routine marks dead tuples as unused and compacts out free
 *		space on their pages.  Pages not having dead tuples recorded from
 *		lazy_scan_heap are not visited at all.
 *
 * Note: the reason for doing this as a second pass is we cannot remove
 * the tuples until we've removed their index entries, and we want to
 * process index entry removal in batches as large as possible.
 */
static void
lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats)
{
	MIRROREDLOCK_BUFMGR_DECLARE;

	int			tupindex;
	int			npages;
	PGRUsage	ru0;

	pg_rusage_init(&ru0);
	npages = 0;

	tupindex = 0;

	/* Fetch gp_persistent_relation_node information that will be added to XLOG record. */
	RelationFetchGpRelationNodeForXLog(onerel);

	while (tupindex < vacrelstats->num_dead_tuples)
	{
		BlockNumber tblk;
		Buffer		buf;
		Page		page;

		vacuum_delay_point();

		tblk = ItemPointerGetBlockNumber(&vacrelstats->dead_tuples[tupindex]);

		/* -------- MirroredLock ---------- */
		MIRROREDLOCK_BUFMGR_LOCK;

		buf = ReadBuffer(onerel, tblk);
		LockBufferForCleanup(buf);
		tupindex = lazy_vacuum_page(onerel, tblk, buf, tupindex, vacrelstats);
		/* Now that we've compacted the page, record its available space */
		page = BufferGetPage(buf);
		lazy_record_free_space(vacrelstats, tblk,
							   PageGetFreeSpace(page));
		UnlockReleaseBuffer(buf);

		MIRROREDLOCK_BUFMGR_UNLOCK;
		/* -------- MirroredLock ---------- */

		npages++;
	}

	ereport(elevel,
			(errmsg("\"%s\": removed %d row versions in %d pages",
					RelationGetRelationName(onerel),
					tupindex, npages),
			 errdetail("%s.",
					   pg_rusage_show(&ru0))));
}

/*
 * Release resources associated with a BrinBuildState.
 */
static void
terminate_brin_buildstate(BrinBuildState *state)
{
	/* release the last index buffer used */
	if (!BufferIsInvalid(state->bs_currentInsertBuf))
	{
		Page		page;

		page = BufferGetPage(state->bs_currentInsertBuf);
		RecordPageWithFreeSpace(state->bs_irel,
							BufferGetBlockNumber(state->bs_currentInsertBuf),
								PageGetFreeSpace(page));
		ReleaseBuffer(state->bs_currentInsertBuf);
	}

	brin_free_desc(state->bs_bdesc);
	pfree(state->bs_dtuple);
	pfree(state);
}

/*
 * 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
gist_dumptree(Relation r, int level, BlockNumber blk, OffsetNumber coff)
{
	Buffer		buffer;
	Page		page;
	GISTPageOpaque opaque;
	IndexTuple	which;
	ItemId		iid;
	OffsetNumber i,
				maxoff;
	BlockNumber cblk;
	char	   *pred;

	pred = (char *) palloc(sizeof(char) * level + 1);
	MemSet(pred, '\t', level);
	pred[level] = '\0';

	buffer = ReadBuffer(r, blk);
	page = (Page) BufferGetPage(buffer);
	opaque = (GISTPageOpaque) PageGetSpecialPointer(page);

	maxoff = PageGetMaxOffsetNumber(page);

	elog(DEBUG4, "%sPage: %d %s blk: %d maxoff: %d free: %d", pred,
		 coff, (opaque->flags & F_LEAF) ? "LEAF" : "INTE", (int) blk,
		 (int) maxoff, PageGetFreeSpace(page));

	for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
	{
		iid = PageGetItemId(page, i);
		which = (IndexTuple) PageGetItem(page, iid);
		cblk = ItemPointerGetBlockNumber(&(which->t_tid));
#ifdef PRINTTUPLE
		elog(DEBUG4, "%s  Tuple. blk: %d size: %d", pred, (int) cblk,
			 IndexTupleSize(which));
#endif

		if (!(opaque->flags & F_LEAF))
			gist_dumptree(r, level + 1, cblk, i);
	}
	ReleaseBuffer(buffer);
	pfree(pred);
}

static bool
entryIsEnoughSpace(GinBtree btree, Buffer buf, OffsetNumber off)
{
	Size		itupsz = 0;
	Page		page = BufferGetPage(buf);

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

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

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

	if (PageGetFreeSpace(page) + itupsz >= MAXALIGN(IndexTupleSize(btree->entry)) + sizeof(ItemIdData))
		return true;

	return false;
}

/*
 * pgstat_index_page -- for generic index page
 */
static void
pgstat_index_page(pgstattuple_type *stat, Page page,
				  OffsetNumber minoff, OffsetNumber maxoff)
{
	OffsetNumber i;

	stat->free_space += PageGetFreeSpace(page);

	for (i = minoff; i <= maxoff; i = OffsetNumberNext(i))
	{
		ItemId		itemid = PageGetItemId(page, i);

		if (ItemIdIsDead(itemid))
		{
			stat->dead_tuple_count++;
			stat->dead_tuple_len += ItemIdGetLength(itemid);
		}
		else
		{
			stat->tuple_count++;
			stat->tuple_len += ItemIdGetLength(itemid);
		}
	}
}

/*
 * pgstattuple_real
 *
 * The real work occurs here
 */
static Datum
pgstattuple_real(Relation rel, FunctionCallInfo fcinfo)
{
	HeapScanDesc scan;
	HeapTuple	tuple;
	BlockNumber nblocks;
	BlockNumber block = 0;		/* next block to count free space in */
	BlockNumber tupblock;
	Buffer		buffer;
	uint64		table_len;
	uint64		tuple_len = 0;
	uint64		dead_tuple_len = 0;
	uint64		tuple_count = 0;
	uint64		dead_tuple_count = 0;
	double		tuple_percent;
	double		dead_tuple_percent;
	uint64		free_space = 0; /* free/reusable space in bytes */
	double		free_percent;	/* free/reusable space in % */
	TupleDesc	tupdesc;
	AttInMetadata *attinmeta;
	char	  **values;
	int			i;
	Datum		result;

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

	/* make sure we have a persistent copy of the tupdesc */
	tupdesc = CreateTupleDescCopy(tupdesc);

	/*
	 * Generate attribute metadata needed later to produce tuples from raw C
	 * strings
	 */
	attinmeta = TupleDescGetAttInMetadata(tupdesc);

	scan = heap_beginscan(rel, SnapshotAny, 0, NULL);

	nblocks = scan->rs_nblocks; /* # blocks to be scanned */

	/* scan the relation */
	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
	{
		/* must hold a buffer lock to call HeapTupleSatisfiesNow */
		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);

		if (HeapTupleSatisfiesNow(tuple->t_data, scan->rs_cbuf))
		{
			tuple_len += tuple->t_len;
			tuple_count++;
		}
		else
		{
			dead_tuple_len += tuple->t_len;
			dead_tuple_count++;
		}

		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);

		/*
		 * To avoid physically reading the table twice, try to do the
		 * free-space scan in parallel with the heap scan.	However,
		 * heap_getnext may find no tuples on a given page, so we cannot
		 * simply examine the pages returned by the heap scan.
		 */
		tupblock = BlockIdGetBlockNumber(&tuple->t_self.ip_blkid);

		while (block <= tupblock)
		{
			buffer = ReadBuffer(rel, block);
			LockBuffer(buffer, BUFFER_LOCK_SHARE);
			free_space += PageGetFreeSpace((Page) BufferGetPage(buffer));
			LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
			ReleaseBuffer(buffer);
			block++;
		}
	}
	heap_endscan(scan);

	while (block < nblocks)
	{
		buffer = ReadBuffer(rel, block);
		free_space += PageGetFreeSpace((Page) BufferGetPage(buffer));
		ReleaseBuffer(buffer);
		block++;
	}

	heap_close(rel, AccessShareLock);

	table_len = (uint64) nblocks *BLCKSZ;

	if (nblocks == 0)
	{
		tuple_percent = 0.0;
//.........这里部分代码省略.........

/*
 *	_hash_doinsert() -- Handle insertion of a single HashItem in the table.
 *
 *		This routine is called by the public interface routines, hashbuild
 *		and hashinsert.  By here, hashitem is completely filled in.
 *		The datum to be used as a "key" is in the hashitem.
 */
InsertIndexResult
_hash_doinsert(Relation rel, HashItem hitem)
{
	Buffer		buf;
	Buffer		metabuf;
	HashMetaPage metap;
	IndexTuple	itup;
	BlockNumber itup_blkno;
	OffsetNumber itup_off;
	InsertIndexResult res;
	BlockNumber blkno;
	Page		page;
	HashPageOpaque pageopaque;
	Size		itemsz;
	bool		do_expand;
	uint32		hashkey;
	Bucket		bucket;
	Datum		datum;
	bool		isnull;

	/*
	 * Compute the hash key for the item.  We do this first so as not to
	 * need to hold any locks while running the hash function.
	 */
	itup = &(hitem->hash_itup);
	if (rel->rd_rel->relnatts != 1)
		elog(ERROR, "hash indexes support only one index key");
	datum = index_getattr(itup, 1, RelationGetDescr(rel), &isnull);
	Assert(!isnull);
	hashkey = _hash_datum2hashkey(rel, datum);

	/* compute item size too */
	itemsz = IndexTupleDSize(hitem->hash_itup)
		+ (sizeof(HashItemData) - sizeof(IndexTupleData));

	itemsz = MAXALIGN(itemsz);	/* be safe, PageAddItem will do this but
								 * we need to be consistent */

	/*
	 * Acquire shared split lock so we can compute the target bucket
	 * safely (see README).
	 */
	_hash_getlock(rel, 0, HASH_SHARE);

	/* Read the metapage */
	metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_READ);
	metap = (HashMetaPage) BufferGetPage(metabuf);
	_hash_checkpage(rel, (Page) metap, LH_META_PAGE);

	/*
	 * Check whether the item can fit on a hash page at all. (Eventually,
	 * we ought to try to apply TOAST methods if not.)  Note that at this
	 * point, itemsz doesn't include the ItemId.
	 */
	if (itemsz > HashMaxItemSize((Page) metap))
		ereport(ERROR,
				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
				 errmsg("index row size %lu exceeds hash maximum %lu",
						(unsigned long) itemsz,
						(unsigned long) HashMaxItemSize((Page) metap))));

	/*
	 * Compute the target bucket number, and convert to block number.
	 */
	bucket = _hash_hashkey2bucket(hashkey,
								  metap->hashm_maxbucket,
								  metap->hashm_highmask,
								  metap->hashm_lowmask);

	blkno = BUCKET_TO_BLKNO(metap, bucket);

	/* release lock on metapage, but keep pin since we'll need it again */
	_hash_chgbufaccess(rel, metabuf, HASH_READ, HASH_NOLOCK);

	/*
	 * Acquire share lock on target bucket; then we can release split lock.
	 */
	_hash_getlock(rel, blkno, HASH_SHARE);

	_hash_droplock(rel, 0, HASH_SHARE);

	/* Fetch the primary bucket page for the bucket */
	buf = _hash_getbuf(rel, blkno, HASH_WRITE);
	page = BufferGetPage(buf);
	_hash_checkpage(rel, page, LH_BUCKET_PAGE);
	pageopaque = (HashPageOpaque) PageGetSpecialPointer(page);
	Assert(pageopaque->hasho_bucket == bucket);

	/* Do the insertion */
	while (PageGetFreeSpace(page) < itemsz)
	{
		/*
		 * no space on this page; check for an overflow page
//.........这里部分代码省略.........

//.........这里部分代码省略.........
		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);
			ooffnum = FirstOffsetNumber;
			omaxoffnum = PageGetMaxOffsetNumber(opage);
			continue;
		}

		/*
		 * Re-hash the tuple to determine which bucket it now belongs in.
		 *
		 * It is annoying to call the hash function while holding locks,
		 * but releasing and relocking the page for each tuple is unappealing
		 * too.
		 */
		hitem = (HashItem) PageGetItem(opage, PageGetItemId(opage, ooffnum));
		itup = &(hitem->hash_itup);
		datum = index_getattr(itup, 1, itupdesc, &null);
		Assert(!null);

		bucket = _hash_hashkey2bucket(_hash_datum2hashkey(rel, datum),
									  maxbucket, highmask, lowmask);

		if (bucket == nbucket)
		{
			/*
			 * insert the tuple into the new bucket.  if it doesn't fit on
			 * the current page in the new bucket, we must allocate a new
			 * overflow page and place the tuple on that page instead.
			 */
			itemsz = IndexTupleDSize(hitem->hash_itup)
				+ (sizeof(HashItemData) - sizeof(IndexTupleData));

			itemsz = MAXALIGN(itemsz);

			if (PageGetFreeSpace(npage) < itemsz)
			{
				/* write out nbuf and drop lock, but keep pin */
				_hash_chgbufaccess(rel, nbuf, HASH_WRITE, HASH_NOLOCK);
				/* chain to a new overflow page */
				nbuf = _hash_addovflpage(rel, metabuf, nbuf);
				npage = BufferGetPage(nbuf);
				_hash_checkpage(rel, npage, LH_OVERFLOW_PAGE);
				/* we don't need nopaque within the loop */
			}

			noffnum = OffsetNumberNext(PageGetMaxOffsetNumber(npage));
			if (PageAddItem(npage, (Item) hitem, itemsz, noffnum, LP_USED)
				== InvalidOffsetNumber)
				elog(ERROR, "failed to add index item to \"%s\"",
					 RelationGetRelationName(rel));

			/*
			 * now delete the tuple from the old bucket.  after this
			 * section of code, 'ooffnum' will actually point to the
			 * ItemId to which we would point if we had advanced it before
			 * the deletion (PageIndexTupleDelete repacks the ItemId
			 * array).	this also means that 'omaxoffnum' is exactly one
			 * less than it used to be, so we really can just decrement it
			 * instead of calling PageGetMaxOffsetNumber.
			 */
			PageIndexTupleDelete(opage, ooffnum);
			omaxoffnum = OffsetNumberPrev(omaxoffnum);
		}
		else
		{
			/*
			 * the tuple stays on this page.  we didn't move anything, so
			 * we didn't delete anything and therefore we don't have to
			 * change 'omaxoffnum'.
			 */
			Assert(bucket == obucket);
			ooffnum = OffsetNumberNext(ooffnum);
		}
	}

	/*
	 * We're at the end of the old bucket chain, so we're done partitioning
	 * the tuples.  Before quitting, call _hash_squeezebucket to ensure the
	 * tuples remaining in the old bucket (including the overflow pages) are
	 * packed as tightly as possible.  The new bucket is already tight.
	 */
	_hash_wrtbuf(rel, obuf);
	_hash_wrtbuf(rel, nbuf);

	_hash_squeezebucket(rel, obucket, start_oblkno);
}