C++ OffsetNumberNext函数代码示例

/*
 * The GiST PickSplit method
 *
 * New linear algorithm, see 'New Linear Node Splitting Algorithm for R-tree',
 * C.H.Ang and T.C.Tan
 */
Datum
gist_box_picksplit(PG_FUNCTION_ARGS)
{
	GistEntryVector *entryvec = (GistEntryVector *) PG_GETARG_POINTER(0);
	GIST_SPLITVEC *v = (GIST_SPLITVEC *) PG_GETARG_POINTER(1);
	OffsetNumber i;
	OffsetNumber *listL,
			   *listR,
			   *listB,
			   *listT;
	BOX		   *unionL,
			   *unionR,
			   *unionB,
			   *unionT;
	int			posL,
				posR,
				posB,
				posT;
	BOX			pageunion;
	BOX		   *cur;
	char		direction = ' ';
	bool		allisequal = true;
	OffsetNumber maxoff;
	int			nbytes;

	posL = posR = posB = posT = 0;
	maxoff = entryvec->n - 1;

	cur = DatumGetBoxP(entryvec->vector[FirstOffsetNumber].key);
	memcpy((void *) &pageunion, (void *) cur, sizeof(BOX));

	/* find MBR */
	for (i = OffsetNumberNext(FirstOffsetNumber); i <= maxoff; i = OffsetNumberNext(i))
	{
		cur = DatumGetBoxP(entryvec->vector[i].key);
		if (allisequal == true && (
								   pageunion.high.x != cur->high.x ||
								   pageunion.high.y != cur->high.y ||
								   pageunion.low.x != cur->low.x ||
								   pageunion.low.y != cur->low.y
								   ))
			allisequal = false;

		adjustBox(&pageunion, cur);
	}

	if (allisequal)
	{
		/*
		 * All entries are the same
		 */
		fallbackSplit(entryvec, v);
		PG_RETURN_POINTER(v);
	}

	nbytes = (maxoff + 2) * sizeof(OffsetNumber);
	listL = (OffsetNumber *) palloc(nbytes);
	listR = (OffsetNumber *) palloc(nbytes);
	listB = (OffsetNumber *) palloc(nbytes);
	listT = (OffsetNumber *) palloc(nbytes);
	unionL = (BOX *) palloc(sizeof(BOX));
	unionR = (BOX *) palloc(sizeof(BOX));
	unionB = (BOX *) palloc(sizeof(BOX));
	unionT = (BOX *) palloc(sizeof(BOX));

#define ADDLIST( list, unionD, pos, num ) do { \
	if ( pos ) { \
		if ( (unionD)->high.x < cur->high.x ) (unionD)->high.x	= cur->high.x; \
		if ( (unionD)->low.x  > cur->low.x	) (unionD)->low.x	= cur->low.x; \
		if ( (unionD)->high.y < cur->high.y ) (unionD)->high.y	= cur->high.y; \
		if ( (unionD)->low.y  > cur->low.y	) (unionD)->low.y	= cur->low.y; \
	} else { \
			memcpy( (void*)(unionD), (void*) cur, sizeof( BOX ) );	\
	} \
	(list)[pos] = num; \
	(pos)++; \
} while(0)

	for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
	{
		cur = DatumGetBoxP(entryvec->vector[i].key);
		if (cur->low.x - pageunion.low.x < pageunion.high.x - cur->high.x)
			ADDLIST(listL, unionL, posL, i);
		else
			ADDLIST(listR, unionR, posR, i);
		if (cur->low.y - pageunion.low.y < pageunion.high.y - cur->high.y)
			ADDLIST(listB, unionB, posB, i);
		else
			ADDLIST(listT, unionT, posT, i);
	}

#define LIMIT_RATIO 0.1
#define _IS_BADRATIO(x,y)	( (y) == 0 || (float)(x)/(float)(y) < LIMIT_RATIO )
#define IS_BADRATIO(x,y) ( _IS_BADRATIO((x),(y)) || _IS_BADRATIO((y),(x)) )
//.........这里部分代码省略.........

/*
** The GiST PickSplit method for segments
** We use Guttman's poly time split algorithm
*/
GIST_SPLITVEC *
gseg_picksplit(GistEntryVector *entryvec,
			   GIST_SPLITVEC *v)
{
	OffsetNumber i,
				j;
	SEG		   *datum_alpha,
			   *datum_beta;
	SEG		   *datum_l,
			   *datum_r;
	SEG		   *union_d,
			   *union_dl,
			   *union_dr;
	SEG		   *inter_d;
	bool		firsttime;
	float		size_alpha,
				size_beta,
				size_union,
				size_inter;
	float		size_waste,
				waste;
	float		size_l,
				size_r;
	int			nbytes;
	OffsetNumber seed_1 = 1,
				seed_2 = 2;
	OffsetNumber *left,
			   *right;
	OffsetNumber maxoff;

#ifdef GIST_DEBUG
	fprintf(stderr, "picksplit\n");
#endif

	maxoff = entryvec->n - 2;
	nbytes = (maxoff + 2) * sizeof(OffsetNumber);
	v->spl_left = (OffsetNumber *) palloc(nbytes);
	v->spl_right = (OffsetNumber *) palloc(nbytes);

	firsttime = true;
	waste = 0.0;

	for (i = FirstOffsetNumber; i < maxoff; i = OffsetNumberNext(i))
	{
		datum_alpha = (SEG *) DatumGetPointer(entryvec->vector[i].key);
		for (j = OffsetNumberNext(i); j <= maxoff; j = OffsetNumberNext(j))
		{
			datum_beta = (SEG *) DatumGetPointer(entryvec->vector[j].key);

			/* compute the wasted space by unioning these guys */
			/* size_waste = size_union - size_inter; */
			union_d = seg_union(datum_alpha, datum_beta);
			rt_seg_size(union_d, &size_union);
			inter_d = seg_inter(datum_alpha, datum_beta);
			rt_seg_size(inter_d, &size_inter);
			size_waste = size_union - size_inter;

			/*
			 * are these a more promising split that what we've already seen?
			 */
			if (size_waste > waste || firsttime)
			{
				waste = size_waste;
				seed_1 = i;
				seed_2 = j;
				firsttime = false;
			}
		}
	}

	left = v->spl_left;
	v->spl_nleft = 0;
	right = v->spl_right;
	v->spl_nright = 0;

	datum_alpha = (SEG *) DatumGetPointer(entryvec->vector[seed_1].key);
	datum_l = seg_union(datum_alpha, datum_alpha);
	rt_seg_size(datum_l, &size_l);
	datum_beta = (SEG *) DatumGetPointer(entryvec->vector[seed_2].key);
	datum_r = seg_union(datum_beta, datum_beta);
	rt_seg_size(datum_r, &size_r);

	/*
	 * Now split up the regions between the two seeds.	An important property
	 * of this split algorithm is that the split vector v has the indices of
	 * items to be split in order in its left and right vectors.  We exploit
	 * this property by doing a merge in the code that actually splits the
	 * page.
	 *
	 * For efficiency, we also place the new index tuple in this loop. This is
	 * handled at the very end, when we have placed all the existing tuples
	 * and i == maxoff + 1.
	 */

	maxoff = OffsetNumberNext(maxoff);
	for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
//.........这里部分代码省略.........

/*
 * Helper function to perform deletion of index entries from a bucket.
 *
 * This function expects that the caller has acquired a cleanup lock on the
 * primary bucket page, and will return with a write lock again held on the
 * primary bucket page.  The lock won't necessarily be held continuously,
 * though, because we'll release it when visiting overflow pages.
 *
 * It would be very bad if this function cleaned a page while some other
 * backend was in the midst of scanning it, because hashgettuple assumes
 * that the next valid TID will be greater than or equal to the current
 * valid TID.  There can't be any concurrent scans in progress when we first
 * enter this function because of the cleanup lock we hold on the primary
 * bucket page, but as soon as we release that lock, there might be.  We
 * handle that by conspiring to prevent those scans from passing our cleanup
 * scan.  To do that, we lock the next page in the bucket chain before
 * releasing the lock on the previous page.  (This type of lock chaining is
 * not ideal, so we might want to look for a better solution at some point.)
 *
 * We need to retain a pin on the primary bucket to ensure that no concurrent
 * split can start.
 */
void
hashbucketcleanup(Relation rel, Bucket cur_bucket, Buffer bucket_buf,
				  BlockNumber bucket_blkno, BufferAccessStrategy bstrategy,
				  uint32 maxbucket, uint32 highmask, uint32 lowmask,
				  double *tuples_removed, double *num_index_tuples,
				  bool split_cleanup,
				  IndexBulkDeleteCallback callback, void *callback_state)
{
	BlockNumber blkno;
	Buffer		buf;
	Bucket new_bucket PG_USED_FOR_ASSERTS_ONLY = InvalidBucket;
	bool		bucket_dirty = false;

	blkno = bucket_blkno;
	buf = bucket_buf;

	if (split_cleanup)
		new_bucket = _hash_get_newbucket_from_oldbucket(rel, cur_bucket,
														lowmask, maxbucket);

	/* Scan each page in bucket */
	for (;;)
	{
		HashPageOpaque opaque;
		OffsetNumber offno;
		OffsetNumber maxoffno;
		Buffer		next_buf;
		Page		page;
		OffsetNumber deletable[MaxOffsetNumber];
		int			ndeletable = 0;
		bool		retain_pin = false;
		bool		clear_dead_marking = false;

		vacuum_delay_point();

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

		/* Scan each tuple in page */
		maxoffno = PageGetMaxOffsetNumber(page);
		for (offno = FirstOffsetNumber;
			 offno <= maxoffno;
			 offno = OffsetNumberNext(offno))
		{
			ItemPointer htup;
			IndexTuple	itup;
			Bucket		bucket;
			bool		kill_tuple = false;

			itup = (IndexTuple) PageGetItem(page,
											PageGetItemId(page, offno));
			htup = &(itup->t_tid);

			/*
			 * To remove the dead tuples, we strictly want to rely on results
			 * of callback function.  refer btvacuumpage for detailed reason.
			 */
			if (callback && callback(htup, callback_state))
			{
				kill_tuple = true;
				if (tuples_removed)
					*tuples_removed += 1;
			}
			else if (split_cleanup)
			{
				/* delete the tuples that are moved by split. */
				bucket = _hash_hashkey2bucket(_hash_get_indextuple_hashkey(itup),
											  maxbucket,
											  highmask,
											  lowmask);
				/* mark the item for deletion */
				if (bucket != cur_bucket)
				{
					/*
					 * We expect tuples to either belong to curent bucket or
					 * new_bucket.  This is ensured because we don't allow
					 * further splits from bucket that contains garbage. See
					 * comments in _hash_expandtable.
//.........这里部分代码省略.........

/*
 * find entry with lowest penalty
 */
OffsetNumber
gistchoose(Relation r, Page p, IndexTuple it,	/* it has compressed entry */
		   GISTSTATE *giststate)
{
	OffsetNumber maxoff;
	OffsetNumber i;
	OffsetNumber which;
	float		sum_grow,
				which_grow[INDEX_MAX_KEYS];
	GISTENTRY	entry,
				identry[INDEX_MAX_KEYS];
	bool		isnull[INDEX_MAX_KEYS];

	maxoff = PageGetMaxOffsetNumber(p);
	*which_grow = -1.0;
	which = InvalidOffsetNumber;
	sum_grow = 1;
	gistDeCompressAtt(giststate, r,
					  it, NULL, (OffsetNumber) 0,
					  identry, isnull);

	Assert(maxoff >= FirstOffsetNumber);
	Assert(!GistPageIsLeaf(p));

	for (i = FirstOffsetNumber; i <= maxoff && sum_grow; i = OffsetNumberNext(i))
	{
		int			j;
		IndexTuple	itup = (IndexTuple) PageGetItem(p, PageGetItemId(p, i));

		if (!GistPageIsLeaf(p) && GistTupleIsInvalid(itup))
		{
			ereport(LOG,
					(errmsg("index \"%s\" needs VACUUM or REINDEX to finish crash recovery",
							RelationGetRelationName(r))));
			continue;
		}

		sum_grow = 0;
		for (j = 0; j < r->rd_att->natts; j++)
		{
			Datum		datum;
			float		usize;
			bool		IsNull;

			datum = index_getattr(itup, j + 1, giststate->tupdesc, &IsNull);
			gistdentryinit(giststate, j, &entry, datum, r, p, i,
						   FALSE, IsNull);
			usize = gistpenalty(giststate, j, &entry, IsNull,
								&identry[j], isnull[j]);

			if (which_grow[j] < 0 || usize < which_grow[j])
			{
				which = i;
				which_grow[j] = usize;
				if (j < r->rd_att->natts - 1 && i == FirstOffsetNumber)
					which_grow[j + 1] = -1;
				sum_grow += which_grow[j];
			}
			else if (which_grow[j] == usize)
				sum_grow += usize;
			else
			{
				sum_grow = 1;
				break;
			}
		}
	}

	if (which == InvalidOffsetNumber)
		which = FirstOffsetNumber;

	return which;
}

/*
 * Updates the stack so that child->parent is the correct parent of the
 * child. child->parent must be exclusively locked on entry, and will
 * remain so at exit, but it might not be the same page anymore.
 */
static void
gistFindCorrectParent(Relation r, GISTInsertStack *child)
{
	GISTInsertStack *parent = child->parent;

	gistcheckpage(r, parent->buffer);
	parent->page = (Page) BufferGetPage(parent->buffer);

	/* here we don't need to distinguish between split and page update */
	if (child->downlinkoffnum == InvalidOffsetNumber ||
		parent->lsn != PageGetLSN(parent->page))
	{
		/* parent is changed, look child in right links until found */
		OffsetNumber i,
					maxoff;
		ItemId		iid;
		IndexTuple	idxtuple;
		GISTInsertStack *ptr;

		while (true)
		{
			maxoff = PageGetMaxOffsetNumber(parent->page);
			for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
			{
				iid = PageGetItemId(parent->page, i);
				idxtuple = (IndexTuple) PageGetItem(parent->page, iid);
				if (ItemPointerGetBlockNumber(&(idxtuple->t_tid)) == child->blkno)
				{
					/* yes!!, found */
					child->downlinkoffnum = i;
					return;
				}
			}

			parent->blkno = GistPageGetOpaque(parent->page)->rightlink;
			UnlockReleaseBuffer(parent->buffer);
			if (parent->blkno == InvalidBlockNumber)
			{
				/*
				 * End of chain and still didn't find parent. It's a very-very
				 * rare situation when root splited.
				 */
				break;
			}
			parent->buffer = ReadBuffer(r, parent->blkno);
			LockBuffer(parent->buffer, GIST_EXCLUSIVE);
			gistcheckpage(r, parent->buffer);
			parent->page = (Page) BufferGetPage(parent->buffer);
		}

		/*
		 * awful!!, we need search tree to find parent ... , but before we
		 * should release all old parent
		 */

		ptr = child->parent->parent;	/* child->parent already released
										 * above */
		while (ptr)
		{
			ReleaseBuffer(ptr->buffer);
			ptr = ptr->parent;
		}

		/* ok, find new path */
		ptr = parent = gistFindPath(r, child->blkno, &child->downlinkoffnum);

		/* read all buffers as expected by caller */
		/* note we don't lock them or gistcheckpage them here! */
		while (ptr)
		{
			ptr->buffer = ReadBuffer(r, ptr->blkno);
			ptr->page = (Page) BufferGetPage(ptr->buffer);
			ptr = ptr->parent;
		}

		/* install new chain of parents to stack */
		child->parent = parent;

		/* make recursive call to normal processing */
		LockBuffer(child->parent->buffer, GIST_EXCLUSIVE);
		gistFindCorrectParent(r, child);
	}

	return;
}

/*
** The GiST PickSplit method for _intments
** We use Guttman's poly time split algorithm
*/
Datum
g_int_picksplit(PG_FUNCTION_ARGS)
{
    GistEntryVector *entryvec = (GistEntryVector *) PG_GETARG_POINTER(0);
    GIST_SPLITVEC *v = (GIST_SPLITVEC *) PG_GETARG_POINTER(1);
    OffsetNumber i,
                 j;
    ArrayType  *datum_alpha,
               *datum_beta;
    ArrayType  *datum_l,
               *datum_r;
    ArrayType  *union_d,
               *union_dl,
               *union_dr;
    ArrayType  *inter_d;
    bool		firsttime;
    float		size_alpha,
                size_beta,
                size_union,
                size_inter;
    float		size_waste,
                waste;
    float		size_l,
                size_r;
    int			nbytes;
    OffsetNumber seed_1 = 0,
                 seed_2 = 0;
    OffsetNumber *left,
                 *right;
    OffsetNumber maxoff;
    SPLITCOST  *costvector;

#ifdef GIST_DEBUG
    elog(DEBUG3, "--------picksplit %d", entryvec->n);
#endif

    maxoff = entryvec->n - 2;
    nbytes = (maxoff + 2) * sizeof(OffsetNumber);
    v->spl_left = (OffsetNumber *) palloc(nbytes);
    v->spl_right = (OffsetNumber *) palloc(nbytes);

    firsttime = true;
    waste = 0.0;
    for (i = FirstOffsetNumber; i < maxoff; i = OffsetNumberNext(i))
    {
        datum_alpha = GETENTRY(entryvec, i);
        for (j = OffsetNumberNext(i); j <= maxoff; j = OffsetNumberNext(j))
        {
            datum_beta = GETENTRY(entryvec, j);

            /* compute the wasted space by unioning these guys */
            /* size_waste = size_union - size_inter; */
            union_d = inner_int_union(datum_alpha, datum_beta);
            rt__int_size(union_d, &size_union);
            inter_d = inner_int_inter(datum_alpha, datum_beta);
            rt__int_size(inter_d, &size_inter);
            size_waste = size_union - size_inter;

            pfree(union_d);

            if (inter_d != (ArrayType *) NULL)
                pfree(inter_d);

            /*
             * are these a more promising split that what we've already seen?
             */

            if (size_waste > waste || firsttime)
            {
                waste = size_waste;
                seed_1 = i;
                seed_2 = j;
                firsttime = false;
            }
        }
    }

    left = v->spl_left;
    v->spl_nleft = 0;
    right = v->spl_right;
    v->spl_nright = 0;
    if (seed_1 == 0 || seed_2 == 0)
    {
        seed_1 = 1;
        seed_2 = 2;
    }

    datum_alpha = GETENTRY(entryvec, seed_1);
    datum_l = copy_intArrayType(datum_alpha);
    rt__int_size(datum_l, &size_l);
    datum_beta = GETENTRY(entryvec, seed_2);
    datum_r = copy_intArrayType(datum_beta);
    rt__int_size(datum_r, &size_r);

    maxoff = OffsetNumberNext(maxoff);

//.........这里部分代码省略.........

/*
 * _hash_splitbucket -- split 'obucket' into 'obucket' and 'nbucket'
 *
 * This routine is used to partition the tuples between old and new bucket and
 * is used to finish the incomplete split operations.  To finish the previously
 * interrupted split operation, the caller needs to fill htab.  If htab is set,
 * then we skip the movement of tuples that exists in htab, otherwise NULL
 * value of htab indicates movement of all the tuples that belong to the new
 * bucket.
 *
 * 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.
 *
 * The caller must hold cleanup 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.)
 *
 * Split needs to retain pin on primary bucket pages of both old and new
 * buckets till end of operation.  This is to prevent vacuum from starting
 * while a split is in progress.
 *
 * In addition, the caller must have created the new bucket's base page,
 * which is passed in buffer nbuf, pinned and write-locked.  The lock will be
 * released here and pin must be released by the caller.  (The API is set up
 * this way because we must do _hash_getnewbuf() before releasing the metapage
 * write lock.  So instead of passing the new bucket's start block number, we
 * pass an actual buffer.)
 */
static void
_hash_splitbucket(Relation rel,
				  Buffer metabuf,
				  Bucket obucket,
				  Bucket nbucket,
				  Buffer obuf,
				  Buffer nbuf,
				  HTAB *htab,
				  uint32 maxbucket,
				  uint32 highmask,
				  uint32 lowmask)
{
	Buffer		bucket_obuf;
	Buffer		bucket_nbuf;
	Page		opage;
	Page		npage;
	HashPageOpaque oopaque;
	HashPageOpaque nopaque;
	OffsetNumber itup_offsets[MaxIndexTuplesPerPage];
	IndexTuple	itups[MaxIndexTuplesPerPage];
	Size		all_tups_size = 0;
	int			i;
	uint16		nitups = 0;

	bucket_obuf = obuf;
	opage = BufferGetPage(obuf);
	oopaque = (HashPageOpaque) PageGetSpecialPointer(opage);

	bucket_nbuf = nbuf;
	npage = BufferGetPage(nbuf);
	nopaque = (HashPageOpaque) PageGetSpecialPointer(npage);

	/*
	 * 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.  Outer loop iterates
	 * once per page in old bucket.
	 */
	for (;;)
	{
		BlockNumber oblkno;
		OffsetNumber ooffnum;
		OffsetNumber omaxoffnum;

		/* Scan each tuple in old page */
		omaxoffnum = PageGetMaxOffsetNumber(opage);
		for (ooffnum = FirstOffsetNumber;
			 ooffnum <= omaxoffnum;
			 ooffnum = OffsetNumberNext(ooffnum))
		{
			IndexTuple	itup;
			Size		itemsz;
			Bucket		bucket;
			bool		found = false;

			/* skip dead tuples */
			if (ItemIdIsDead(PageGetItemId(opage, ooffnum)))
				continue;

			/*
			 * Before inserting a tuple, probe the hash table containing TIDs
			 * of tuples belonging to new bucket, if we find a match, then
			 * skip that tuple, else fetch the item's hash key (conveniently
			 * stored in the item) and determine which bucket it now belongs
			 * in.
			 */
			itup = (IndexTuple) PageGetItem(opage,
											PageGetItemId(opage, ooffnum));
//.........这里部分代码省略.........

Datum
readindex(PG_FUNCTION_ARGS)
{
	FuncCallContext	   *funcctx;
	readindexinfo	   *info;

	MIRROREDLOCK_BUFMGR_DECLARE;

	if (SRF_IS_FIRSTCALL())
	{
		Oid		irelid = PG_GETARG_OID(0);
		TupleDesc	tupdesc;
		MemoryContext oldcontext;
		AttrNumber		outattnum;
		Relation	irel;
		TupleDesc	itupdesc;
		int			i;
		AttrNumber	attno;

		irel = index_open(irelid, AccessShareLock);
		itupdesc = RelationGetDescr(irel);
		outattnum = FIXED_COLUMN + itupdesc->natts;

		funcctx = SRF_FIRSTCALL_INIT();
		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
		tupdesc = CreateTemplateTupleDesc(outattnum, false);
		attno = 1;
		TupleDescInitEntry(tupdesc, attno++, "ictid", TIDOID, -1, 0);
		TupleDescInitEntry(tupdesc, attno++, "hctid", TIDOID, -1, 0);
		TupleDescInitEntry(tupdesc, attno++, "aotid", TEXTOID, -1, 0);
		TupleDescInitEntry(tupdesc, attno++, "istatus", TEXTOID, -1, 0);
		TupleDescInitEntry(tupdesc, attno++, "hstatus", TEXTOID, -1, 0);

		for (i = 0; i < itupdesc->natts; i++)
		{
			Form_pg_attribute attr = itupdesc->attrs[i];
			TupleDescInitEntry(tupdesc, attno++, NameStr(attr->attname), attr->atttypid, attr->atttypmod, 0);
		}

		funcctx->tuple_desc = BlessTupleDesc(tupdesc);
		info = (readindexinfo *) palloc(sizeof(readindexinfo));
		funcctx->user_fctx = (void *) info;

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

		MemoryContextSwitchTo(oldcontext);
	}

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

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

		if (info->page == NULL)
		{
			MIRROREDLOCK_BUFMGR_LOCK;
			info->buf = ReadBuffer(info->irel, info->blkno);
			info->page = BufferGetPage(info->buf);
			info->opaque = (BTPageOpaque) PageGetSpecialPointer(info->page);
			info->minoff = P_FIRSTDATAKEY(info->opaque);
			info->maxoff = PageGetMaxOffsetNumber(info->page);
			info->offnum = info->minoff;
			MIRROREDLOCK_BUFMGR_UNLOCK;
		}
		if (!P_ISLEAF(info->opaque) || info->offnum > info->maxoff)
		{
			ReleaseBuffer(info->buf);
			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, values, nulls);

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

		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
		result = HeapTupleGetDatum(tuple);
//.........这里部分代码省略.........

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

			GinPageGetOpaque(page)->rightlink = sublist.head;

			MarkBufferDirty(buffer);

			metadata->tail = sublist.tail;
			metadata->tailFreeSize = sublist.tailFreeSize;

			metadata->nPendingPages += sublist.nPendingPages;
			metadata->nPendingHeapTuples += sublist.nPendingHeapTuples;

			if (needWal)
				XLogRegisterBuffer(1, buffer, REGBUF_STANDARD);
		}
	}
	else
	{
		/*
		 * Insert into tail page.  Metapage is already locked
		 */
		OffsetNumber l,
					off;
		int			i,
					tupsize;
		char	   *ptr;
		char	   *collectordata;

		buffer = ReadBuffer(index, metadata->tail);
		LockBuffer(buffer, GIN_EXCLUSIVE);
		page = BufferGetPage(buffer);

		off = (PageIsEmpty(page)) ? FirstOffsetNumber :
			OffsetNumberNext(PageGetMaxOffsetNumber(page));

		collectordata = ptr = (char *) palloc(collector->sumsize);

		data.ntuples = collector->ntuples;

		if (needWal)
			XLogBeginInsert();

		START_CRIT_SECTION();

		/*
		 * Increase counter of heap tuples
		 */
		Assert(GinPageGetOpaque(page)->maxoff <= metadata->nPendingHeapTuples);
		GinPageGetOpaque(page)->maxoff++;
		metadata->nPendingHeapTuples++;

		for (i = 0; i < collector->ntuples; i++)
		{
			tupsize = IndexTupleSize(collector->tuples[i]);
			l = PageAddItem(page, (Item) collector->tuples[i], tupsize, off, false, false);

			if (l == InvalidOffsetNumber)
				elog(ERROR, "failed to add item to index page in \"%s\"",
					 RelationGetRelationName(index));

			memcpy(ptr, collector->tuples[i], tupsize);
			ptr += tupsize;

			off++;
		}

/*
 *	hashgettuple() -- Get the next tuple in the scan.
 */
Datum
hashgettuple(PG_FUNCTION_ARGS)
{
	IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
	ScanDirection dir = (ScanDirection) PG_GETARG_INT32(1);
	HashScanOpaque so = (HashScanOpaque) scan->opaque;
	Relation	rel = scan->indexRelation;
	Buffer		buf;
	Page		page;
	OffsetNumber offnum;
	ItemPointer current;
	bool		res;

	/* Hash indexes are always lossy since we store only the hash code */
	scan->xs_recheck = true;

	/*
	 * We hold pin but not lock on current buffer while outside the hash AM.
	 * Reacquire the read lock here.
	 */
	if (BufferIsValid(so->hashso_curbuf))
		_hash_chgbufaccess(rel, so->hashso_curbuf, HASH_NOLOCK, HASH_READ);

	/*
	 * If we've already initialized this scan, we can just advance it in the
	 * appropriate direction.  If we haven't done so yet, we call a routine to
	 * get the first item in the scan.
	 */
	current = &(so->hashso_curpos);
	if (ItemPointerIsValid(current))
	{
		/*
		 * An insertion into the current index page could have happened while
		 * we didn't have read lock on it.  Re-find our position by looking
		 * for the TID we previously returned.	(Because we hold share lock on
		 * the bucket, no deletions or splits could have occurred; therefore
		 * we can expect that the TID still exists in the current index page,
		 * at an offset >= where we were.)
		 */
		OffsetNumber maxoffnum;

		buf = so->hashso_curbuf;
		Assert(BufferIsValid(buf));
		page = BufferGetPage(buf);
		maxoffnum = PageGetMaxOffsetNumber(page);
		for (offnum = ItemPointerGetOffsetNumber(current);
			 offnum <= maxoffnum;
			 offnum = OffsetNumberNext(offnum))
		{
			IndexTuple	itup;

			itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
			if (ItemPointerEquals(&(so->hashso_heappos), &(itup->t_tid)))
				break;
		}
		if (offnum > maxoffnum)
			elog(ERROR, "failed to re-find scan position within index \"%s\"",
				 RelationGetRelationName(rel));
		ItemPointerSetOffsetNumber(current, offnum);

		/*
		 * Check to see if we should kill the previously-fetched tuple.
		 */
		if (scan->kill_prior_tuple)
		{
			/*
			 * Yes, so mark it by setting the LP_DEAD state in the item flags.
			 */
			ItemIdMarkDead(PageGetItemId(page, offnum));

			/*
			 * Since this can be redone later if needed, it's treated the same
			 * as a commit-hint-bit status update for heap tuples: we mark the
			 * buffer dirty but don't make a WAL log entry.
			 */
			SetBufferCommitInfoNeedsSave(buf);
		}

		/*
		 * Now continue the scan.
		 */
		res = _hash_next(scan, dir);
	}
	else
		res = _hash_first(scan, dir);

	/*
	 * Skip killed tuples if asked to.
	 */
	if (scan->ignore_killed_tuples)
	{
		while (res)
		{
			offnum = ItemPointerGetOffsetNumber(current);
			page = BufferGetPage(so->hashso_curbuf);
			if (!ItemIdIsDead(PageGetItemId(page, offnum)))
				break;
//.........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.
 *
 * Result: a palloc'd struct containing statistical info for VACUUM displays.
 */
Datum
hashbulkdelete(PG_FUNCTION_ARGS)
{
	IndexVacuumInfo *info = (IndexVacuumInfo *) PG_GETARG_POINTER(0);
	IndexBulkDeleteResult *stats = (IndexBulkDeleteResult *) PG_GETARG_POINTER(1);
	IndexBulkDeleteCallback callback = (IndexBulkDeleteCallback) PG_GETARG_POINTER(2);
	void	   *callback_state = (void *) PG_GETARG_POINTER(3);
	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;
	HashMetaPage metap;
	HashMetaPageData local_metapage;

	tuples_removed = 0;
	num_index_tuples = 0;

	/*
	 * Read the metapage to fetch original bucket and tuple counts.  Also, we
	 * keep a copy of the last-seen metapage so that we can use its
	 * hashm_spares[] values to compute bucket page addresses.	This is a bit
	 * hokey but perfectly safe, since the interesting entries in the spares
	 * array cannot change under us; and it beats rereading the metapage for
	 * each bucket.
	 */
	metabuf = _hash_getbuf(rel, HASH_METAPAGE, HASH_READ, LH_META_PAGE);
	metap = HashPageGetMeta(BufferGetPage(metabuf));
	orig_maxbucket = metap->hashm_maxbucket;
	orig_ntuples = metap->hashm_ntuples;
	memcpy(&local_metapage, metap, sizeof(local_metapage));
	_hash_relbuf(rel, metabuf);

	/* 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;
		bool		bucket_dirty = false;

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

		/* Exclusive-lock the bucket so we can shrink it */
		_hash_getlock(rel, bucket_blkno, HASH_EXCLUSIVE);

		/* Shouldn't have any active scans locally, either */
		if (_hash_has_active_scan(rel, cur_bucket))
			elog(ERROR, "hash index has active scan during VACUUM");

		/* Scan each page in bucket */
		blkno = bucket_blkno;
		while (BlockNumberIsValid(blkno))
		{
			Buffer		buf;
			Page		page;
			HashPageOpaque opaque;
			OffsetNumber offno;
			OffsetNumber maxoffno;
			OffsetNumber deletable[MaxOffsetNumber];
			int			ndeletable = 0;

			vacuum_delay_point();

			buf = _hash_getbuf_with_strategy(rel, blkno, HASH_WRITE,
										   LH_BUCKET_PAGE | LH_OVERFLOW_PAGE,
											 info->strategy);
			page = BufferGetPage(buf);
			opaque = (HashPageOpaque) PageGetSpecialPointer(page);
			Assert(opaque->hasho_bucket == cur_bucket);

			/* Scan each tuple in page */
			maxoffno = PageGetMaxOffsetNumber(page);
			for (offno = FirstOffsetNumber;
				 offno <= maxoffno;
				 offno = OffsetNumberNext(offno))
			{
				IndexTuple	itup;
				ItemPointer htup;

				itup = (IndexTuple) PageGetItem(page,
												PageGetItemId(page, offno));
				htup = &(itup->t_tid);
				if (callback(htup, callback_state))
				{
					/* mark the item for deletion */
//.........这里部分代码省略.........

Datum geography_gist_picksplit(PG_FUNCTION_ARGS)
{

	GistEntryVector	*entryvec = (GistEntryVector*) PG_GETARG_POINTER(0);

	GIST_SPLITVEC *v = (GIST_SPLITVEC*) PG_GETARG_POINTER(1);
	OffsetNumber i;
	/* One union box for each half of the space. */
	GIDX **box_union;
	/* One offset number list for each half of the space. */
	OffsetNumber **list;
	/* One position index for each half of the space. */
	int *pos;
	GIDX *box_pageunion;
	GIDX *box_current;
	int direction = -1;
	bool all_entries_equal = true;
	OffsetNumber max_offset;
	int nbytes, ndims_pageunion, d;
	int posmax = -1;

	POSTGIS_DEBUG(4, "[GIST] 'picksplit' function called");

	/*
	** First calculate the bounding box and maximum number of dimensions in this page.
	*/

	max_offset = entryvec->n - 1;
	box_current = (GIDX*) DatumGetPointer(entryvec->vector[FirstOffsetNumber].key);
	box_pageunion = gidx_copy(box_current);

	/* Calculate the containing box (box_pageunion) for the whole page we are going to split. */
	for ( i = OffsetNumberNext(FirstOffsetNumber); i <= max_offset; i = OffsetNumberNext(i) )
	{
		box_current = (GIDX*) DatumGetPointer(entryvec->vector[i].key);

		if ( all_entries_equal == true && ! gidx_equals (box_pageunion, box_current) )
			all_entries_equal = false;

		gidx_merge( &box_pageunion, box_current );
	}

	POSTGIS_DEBUGF(3, "[GIST] box_pageunion: %s", gidx_to_string(box_pageunion));

	/* Every box in the page is the same! So, we split and just put half the boxes in each child. */
	if ( all_entries_equal )
	{
		POSTGIS_DEBUG(4, "[GIST] picksplit finds all entries equal!");
		geography_gist_picksplit_fallback(entryvec, v);
		PG_RETURN_POINTER(v);
	}

	/* Initialize memory structures. */
	nbytes = (max_offset + 2) * sizeof(OffsetNumber);
	ndims_pageunion = GIDX_NDIMS(box_pageunion);
	POSTGIS_DEBUGF(4, "[GIST] ndims_pageunion == %d", ndims_pageunion);
	pos = palloc(2*ndims_pageunion * sizeof(int));
	list = palloc(2*ndims_pageunion * sizeof(OffsetNumber*));
	box_union = palloc(2*ndims_pageunion * sizeof(GIDX*));
	for ( d = 0; d < ndims_pageunion; d++ )
	{
		list[BELOW(d)] = (OffsetNumber*) palloc(nbytes);
		list[ABOVE(d)] = (OffsetNumber*) palloc(nbytes);
		box_union[BELOW(d)] = gidx_new(ndims_pageunion);
		box_union[ABOVE(d)] = gidx_new(ndims_pageunion);
		pos[BELOW(d)] = 0;
		pos[ABOVE(d)] = 0;
	}

	/*
	** Assign each entry in the node to the volume partitions it belongs to,
	** such as "above the x/y plane, left of the y/z plane, below the x/z plane".
	** Each entry thereby ends up in three of the six partitions.
	*/
	POSTGIS_DEBUG(4, "[GIST] 'picksplit' calculating best split axis");
	for ( i = FirstOffsetNumber; i <= max_offset; i = OffsetNumberNext(i) )
	{
		box_current = (GIDX*) DatumGetPointer(entryvec->vector[i].key);

		for ( d = 0; d < ndims_pageunion; d++ )
		{
			if ( GIDX_GET_MIN(box_current,d)-GIDX_GET_MIN(box_pageunion,d) < GIDX_GET_MAX(box_pageunion,d)-GIDX_GET_MAX(box_current,d) )
			{
				geography_gist_picksplit_addlist(list[BELOW(d)], &(box_union[BELOW(d)]), box_current, &(pos[BELOW(d)]), i);
			}
			else
			{
				geography_gist_picksplit_addlist(list[ABOVE(d)], &(box_union[ABOVE(d)]), box_current, &(pos[ABOVE(d)]), i);
			}

		}

	}

	/*
	** "Bad disposition", too many entries fell into one octant of the space, so no matter which
	** plane we choose to split on, we're going to end up with a mostly full node. Where the
	** data is pretty homogeneous (lots of duplicates) entries that are equidistant from the
	** sides of the page union box can occasionally all end up in one place, leading
	** to this condition.
//.........这里部分代码省略.........

/*
 *	_bt_readpage() -- Load data from current index page into so->currPos
 *
 * Caller must have pinned and read-locked so->currPos.buf; the buffer's state
 * is not changed here.  Also, currPos.moreLeft and moreRight must be valid;
 * they are updated as appropriate.  All other fields of so->currPos are
 * initialized from scratch here.
 *
 * We scan the current page starting at offnum and moving in the indicated
 * direction.  All items matching the scan keys are loaded into currPos.items.
 * moreLeft or moreRight (as appropriate) is cleared if _bt_checkkeys reports
 * that there can be no more matching tuples in the current scan direction.
 *
 * Returns true if any matching items found on the page, false if none.
 */
static bool
_bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum)
{
	BTScanOpaque so = (BTScanOpaque) scan->opaque;
	Page		page;
	BTPageOpaque opaque;
	OffsetNumber minoff;
	OffsetNumber maxoff;
	int			itemIndex;
	bool		continuescan;

	/* we must have the buffer pinned and locked */
	Assert(BufferIsValid(so->currPos.buf));

	page = BufferGetPage(so->currPos.buf);
	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
	minoff = P_FIRSTDATAKEY(opaque);
	maxoff = PageGetMaxOffsetNumber(page);

	/*
	 * we must save the page's right-link while scanning it; this tells us
	 * where to step right to after we're done with these items.  There is no
	 * corresponding need for the left-link, since splits always go right.
	 */
	so->currPos.nextPage = opaque->btpo_next;

	if (ScanDirectionIsForward(dir))
	{
		/* load items[] in ascending order */
		itemIndex = 0;

		offnum = Max(offnum, minoff);

		while (offnum <= maxoff)
		{
			if (_bt_checkkeys(scan, page, offnum, dir, &continuescan))
			{
				/* tuple passes all scan key conditions, so remember it */
				/* _bt_checkkeys put the heap ptr into scan->xs_ctup.t_self */
				so->currPos.items[itemIndex].heapTid = scan->xs_ctup.t_self;
				so->currPos.items[itemIndex].indexOffset = offnum;
				itemIndex++;
			}
			if (!continuescan)
			{
				/* there can't be any more matches, so stop */
				so->currPos.moreRight = false;
				break;
			}

			offnum = OffsetNumberNext(offnum);
		}

		Assert(itemIndex <= MaxIndexTuplesPerPage);
		so->currPos.firstItem = 0;
		so->currPos.lastItem = itemIndex - 1;
		so->currPos.itemIndex = 0;
	}
	else
	{
		/* load items[] in descending order */
		itemIndex = MaxIndexTuplesPerPage;

		offnum = Min(offnum, maxoff);

		while (offnum >= minoff)
		{
			if (_bt_checkkeys(scan, page, offnum, dir, &continuescan))
			{
				/* tuple passes all scan key conditions, so remember it */
				/* _bt_checkkeys put the heap ptr into scan->xs_ctup.t_self */
				itemIndex--;
				so->currPos.items[itemIndex].heapTid = scan->xs_ctup.t_self;
				so->currPos.items[itemIndex].indexOffset = offnum;
			}
			if (!continuescan)
			{
				/* there can't be any more matches, so stop */
				so->currPos.moreLeft = false;
				break;
			}

			offnum = OffsetNumberPrev(offnum);
		}

//.........这里部分代码省略.........

/*
 *	_hash_squeezebucket(rel, bucket)
 *
 *	Try to squeeze the tuples onto pages occurring earlier in the
 *	bucket chain in an attempt to free overflow pages. When we start
 *	the "squeezing", the page from which we start taking tuples (the
 *	"read" page) is the last bucket in the bucket chain and the page
 *	onto which we start squeezing tuples (the "write" page) is the
 *	first page in the bucket chain.  The read page works backward and
 *	the write page works forward; the procedure terminates when the
 *	read page and write page are the same page.
 *
 *	At completion of this procedure, it is guaranteed that all pages in
 *	the bucket are nonempty, unless the bucket is totally empty (in
 *	which case all overflow pages will be freed).  The original implementation
 *	required that to be true on entry as well, but it's a lot easier for
 *	callers to leave empty overflow pages and let this guy clean it up.
 *
 *	Caller must hold exclusive lock on the target bucket.  This allows
 *	us to safely lock multiple pages in the bucket.
 *
 *	Since this function is invoked in VACUUM, we provide an access strategy
 *	parameter that controls fetches of the bucket pages.
 */
void
_hash_squeezebucket(Relation rel,
					Bucket bucket,
					BlockNumber bucket_blkno,
					BufferAccessStrategy bstrategy)
{
	BlockNumber wblkno;
	BlockNumber rblkno;
	Buffer		wbuf;
	Buffer		rbuf;
	Page		wpage;
	Page		rpage;
	HashPageOpaque wopaque;
	HashPageOpaque ropaque;
	bool		wbuf_dirty;

	/*
	 * start squeezing into the base bucket page.
	 */
	wblkno = bucket_blkno;
	wbuf = _hash_getbuf_with_strategy(rel,
									  wblkno,
									  HASH_WRITE,
									  LH_BUCKET_PAGE,
									  bstrategy);
	wpage = BufferGetPage(wbuf);
	wopaque = (HashPageOpaque) PageGetSpecialPointer(wpage);

	/*
	 * if there aren't any overflow pages, there's nothing to squeeze.
	 */
	if (!BlockNumberIsValid(wopaque->hasho_nextblkno))
	{
		_hash_relbuf(rel, wbuf);
		return;
	}

	/*
	 * Find the last page in the bucket chain by starting at the base bucket
	 * page and working forward.  Note: we assume that a hash bucket chain is
	 * usually smaller than the buffer ring being used by VACUUM, else using
	 * the access strategy here would be counterproductive.
	 */
	rbuf = InvalidBuffer;
	ropaque = wopaque;
	do
	{
		rblkno = ropaque->hasho_nextblkno;
		if (rbuf != InvalidBuffer)
			_hash_relbuf(rel, rbuf);
		rbuf = _hash_getbuf_with_strategy(rel,
										  rblkno,
										  HASH_WRITE,
										  LH_OVERFLOW_PAGE,
										  bstrategy);
		rpage = BufferGetPage(rbuf);
		ropaque = (HashPageOpaque) PageGetSpecialPointer(rpage);
		Assert(ropaque->hasho_bucket == bucket);
	} while (BlockNumberIsValid(ropaque->hasho_nextblkno));

	/*
	 * squeeze the tuples.
	 */
	wbuf_dirty = false;
	for (;;)
	{
		OffsetNumber roffnum;
		OffsetNumber maxroffnum;
		OffsetNumber deletable[MaxOffsetNumber];
		int			ndeletable = 0;

		/* Scan each tuple in "read" page */
		maxroffnum = PageGetMaxOffsetNumber(rpage);
		for (roffnum = FirstOffsetNumber;
			 roffnum <= maxroffnum;
			 roffnum = OffsetNumberNext(roffnum))
//.........这里部分代码省略.........

//.........这里部分代码省略.........
											  PageGetItemId(state->page,
															state->offset));
				state->dtup = brin_deform_tuple(state->bdesc, tup);
				state->attno = 1;
				state->unusedItem = false;
			}
			else
				state->unusedItem = true;

			MemoryContextSwitchTo(mctx);
		}
		else
			state->attno++;

		MemSet(nulls, 0, sizeof(nulls));

		if (state->unusedItem)
		{
			values[0] = UInt16GetDatum(state->offset);
			nulls[1] = true;
			nulls[2] = true;
			nulls[3] = true;
			nulls[4] = true;
			nulls[5] = true;
			nulls[6] = true;
		}
		else
		{
			int		att = state->attno - 1;

			values[0] = UInt16GetDatum(state->offset);
			values[1] = UInt32GetDatum(state->dtup->bt_blkno);
			values[2] = UInt16GetDatum(state->attno);
			values[3] = BoolGetDatum(state->dtup->bt_columns[att].bv_allnulls);
			values[4] = BoolGetDatum(state->dtup->bt_columns[att].bv_hasnulls);
			values[5] = BoolGetDatum(state->dtup->bt_placeholder);
			if (!state->dtup->bt_columns[att].bv_allnulls)
			{
				BrinValues   *bvalues = &state->dtup->bt_columns[att];
				StringInfoData	s;
				bool		first;
				int			i;

				initStringInfo(&s);
				appendStringInfoChar(&s, '{');

				first = true;
				for (i = 0; i < state->columns[att]->nstored; i++)
				{
					char   *val;

					if (!first)
						appendStringInfoString(&s, " .. ");
					first = false;
					val = OutputFunctionCall(&state->columns[att]->outputFn[i],
											 bvalues->bv_values[i]);
					appendStringInfoString(&s, val);
					pfree(val);
				}
				appendStringInfoChar(&s, '}');

				values[6] = CStringGetTextDatum(s.data);
				pfree(s.data);
			}
			else
			{
				nulls[6] = true;
			}
		}

		result = heap_form_tuple(fctx->tuple_desc, values, nulls);

		/*
		 * If the item was unused, jump straight to the next one; otherwise,
		 * the only cleanup needed here is to set our signal to go to the next
		 * tuple in the following iteration, by freeing the current one.
		 */
		if (state->unusedItem)
			state->offset = OffsetNumberNext(state->offset);
		else if (state->attno >= state->bdesc->bd_tupdesc->natts)
		{
			pfree(state->dtup);
			state->dtup = NULL;
			state->offset = OffsetNumberNext(state->offset);
		}

		/*
		 * If we're beyond the end of the page, set flag to end the function in
		 * the following iteration.
		 */
		if (state->offset > PageGetMaxOffsetNumber(state->page))
			state->done = true;

		SRF_RETURN_NEXT(fctx, HeapTupleGetDatum(result));
	}

	brin_free_desc(state->bdesc);

	SRF_RETURN_DONE(fctx);
}