rtree.c

关系型数据库 Postgresql 6.5.2

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

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

	leftoff = rightoff = FirstOffsetNumber;
	maxoff = PageGetMaxOffsetNumber(p);
	for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
	{
		itemid = PageGetItemId(p, i);
		item = (IndexTuple) PageGetItem(p, itemid);

		if (i == *(v.spl_left))
		{
			PageAddItem(left, (Item) item, IndexTupleSize(item),
						leftoff, LP_USED);
			leftoff = OffsetNumberNext(leftoff);
			v.spl_left++;		/* advance in left split vector */
		}
		else
		{
			PageAddItem(right, (Item) item, IndexTupleSize(item),
						rightoff, LP_USED);
			rightoff = OffsetNumberNext(rightoff);
			v.spl_right++;		/* advance in right split vector */
		}
	}

	/* build an InsertIndexResult for this insertion */
	res = (InsertIndexResult) palloc(sizeof(InsertIndexResultData));

	/* now insert the new index tuple */
	if (*(v.spl_left) != FirstOffsetNumber)
	{
		PageAddItem(left, (Item) itup, IndexTupleSize(itup),
					leftoff, LP_USED);
		leftoff = OffsetNumberNext(leftoff);
		ItemPointerSet(&(res->pointerData), lbknum, leftoff);
	}
	else
	{
		PageAddItem(right, (Item) itup, IndexTupleSize(itup),
					rightoff, LP_USED);
		rightoff = OffsetNumberNext(rightoff);
		ItemPointerSet(&(res->pointerData), rbknum, rightoff);
	}

	if ((bufblock = BufferGetBlockNumber(buffer)) != P_ROOT)
		PageRestoreTempPage(left, p);
	WriteBuffer(leftbuf);
	WriteBuffer(rightbuf);

	/*
	 * Okay, the page is split.  We have three things left to do:
	 *
	 * 1)  Adjust any active scans on this index to cope with changes we
	 * introduced in its structure by splitting this page.
	 *
	 * 2)  "Tighten" the bounding box of the pointer to the left page in the
	 * parent node in the tree, if any.  Since we moved a bunch of stuff
	 * off the left page, we expect it to get smaller.	This happens in
	 * the internal insertion routine.
	 *
	 * 3)  Insert a pointer to the right page in the parent.  This may cause
	 * the parent to split.  If it does, we need to repeat steps one and
	 * two for each split node in the tree.
	 */

	/* adjust active scans */
	rtadjscans(r, RTOP_SPLIT, bufblock, FirstOffsetNumber);

	tupDesc = r->rd_att;
	ltup = (IndexTuple) index_formtuple(tupDesc,
									  (Datum *) &(v.spl_ldatum), isnull);
	rtup = (IndexTuple) index_formtuple(tupDesc,
									  (Datum *) &(v.spl_rdatum), isnull);
	pfree(isnull);

	/* set pointers to new child pages in the internal index tuples */
	ItemPointerSet(&(ltup->t_tid), lbknum, 1);
	ItemPointerSet(&(rtup->t_tid), rbknum, 1);

	rtintinsert(r, stack, ltup, rtup, rtstate);

	pfree(ltup);
	pfree(rtup);

	return res;
}

static void
rtintinsert(Relation r,
			RTSTACK *stk,
			IndexTuple ltup,
			IndexTuple rtup,
			RTSTATE *rtstate)
{
	IndexTuple	old;
	Buffer		b;
	Page		p;
	char	   *ldatum,
			   *rdatum,
			   *newdatum;
	InsertIndexResult res;

	if (stk == (RTSTACK *) NULL)
	{
		rtnewroot(r, ltup, rtup);
		return;
	}

	b = ReadBuffer(r, stk->rts_blk);
	p = BufferGetPage(b);
	old = (IndexTuple) PageGetItem(p, PageGetItemId(p, stk->rts_child));

	/*
	 * This is a hack.	Right now, we force rtree keys to be constant
	 * size. To fix this, need delete the old key and add both left and
	 * right for the two new pages.  The insertion of left may force a
	 * split if the new left key is bigger than the old key.
	 */

	if (IndexTupleSize(old) != IndexTupleSize(ltup))
		elog(ERROR, "Variable-length rtree keys are not supported.");

	/* install pointer to left child */
	memmove(old, ltup, IndexTupleSize(ltup));

	if (nospace(p, rtup))
	{
		newdatum = (((char *) ltup) + sizeof(IndexTupleData));
		rttighten(r, stk->rts_parent, newdatum,
			   (IndexTupleSize(ltup) - sizeof(IndexTupleData)), rtstate);
		res = dosplit(r, b, stk->rts_parent, rtup, rtstate);
		WriteBuffer(b);			/* don't forget to release buffer!  -
								 * 01/31/94 */
		pfree(res);
	}
	else
	{
		PageAddItem(p, (Item) rtup, IndexTupleSize(rtup),
					PageGetMaxOffsetNumber(p), LP_USED);
		WriteBuffer(b);
		ldatum = (((char *) ltup) + sizeof(IndexTupleData));
		rdatum = (((char *) rtup) + sizeof(IndexTupleData));
		newdatum = (char *) (*fmgr_faddr(&rtstate->unionFn)) (ldatum, rdatum);

		rttighten(r, stk->rts_parent, newdatum,
			   (IndexTupleSize(rtup) - sizeof(IndexTupleData)), rtstate);

		pfree(newdatum);
	}
}

static void
rtnewroot(Relation r, IndexTuple lt, IndexTuple rt)
{
	Buffer		b;
	Page		p;

	b = ReadBuffer(r, P_ROOT);
	RTInitBuffer(b, 0);
	p = BufferGetPage(b);
	PageAddItem(p, (Item) lt, IndexTupleSize(lt),
				FirstOffsetNumber, LP_USED);
	PageAddItem(p, (Item) rt, IndexTupleSize(rt),
				OffsetNumberNext(FirstOffsetNumber), LP_USED);
	WriteBuffer(b);
}

static void
picksplit(Relation r,
		  Page page,
		  SPLITVEC *v,
		  IndexTuple itup,
		  RTSTATE *rtstate)
{
	OffsetNumber maxoff;
	OffsetNumber i,
				j;
	IndexTuple	item_1,
				item_2;
	char	   *datum_alpha,
			   *datum_beta;
	char	   *datum_l,
			   *datum_r;
	char	   *union_d,
			   *union_dl,
			   *union_dr;
	char	   *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;

	maxoff = PageGetMaxOffsetNumber(page);

	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))
	{
		item_1 = (IndexTuple) PageGetItem(page, PageGetItemId(page, i));
		datum_alpha = ((char *) item_1) + sizeof(IndexTupleData);
		for (j = OffsetNumberNext(i); j <= maxoff; j = OffsetNumberNext(j))
		{
			item_2 = (IndexTuple) PageGetItem(page, PageGetItemId(page, j));
			datum_beta = ((char *) item_2) + sizeof(IndexTupleData);

			/* compute the wasted space by unioning these guys */
			union_d = (char *) (*fmgr_faddr(&rtstate->unionFn)) (datum_alpha, datum_beta);
			(*fmgr_faddr(&rtstate->sizeFn)) (union_d, &size_union);
			inter_d = (char *) (*fmgr_faddr(&rtstate->interFn)) (datum_alpha, datum_beta);
			(*fmgr_faddr(&rtstate->sizeFn)) (inter_d, &size_inter);
			size_waste = size_union - size_inter;

			pfree(union_d);

			if (inter_d != (char *) 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;

	item_1 = (IndexTuple) PageGetItem(page, PageGetItemId(page, seed_1));
	datum_alpha = ((char *) item_1) + sizeof(IndexTupleData);
	datum_l = (char *) (*fmgr_faddr(&rtstate->unionFn)) (datum_alpha, datum_alpha);
	(*fmgr_faddr(&rtstate->sizeFn)) (datum_l, &size_l);
	item_2 = (IndexTuple) PageGetItem(page, PageGetItemId(page, seed_2));
	datum_beta = ((char *) item_2) + sizeof(IndexTupleData);
	datum_r = (char *) (*fmgr_faddr(&rtstate->unionFn)) (datum_beta, datum_beta);
	(*fmgr_faddr(&rtstate->sizeFn)) (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))
	{

		/*
		 * If we've already decided where to place this item, just put it
		 * on the right list.  Otherwise, we need to figure out which page
		 * needs the least enlargement in order to store the item.
		 */

		if (i == seed_1)
		{
			*left++ = i;
			v->spl_nleft++;
			continue;
		}
		else if (i == seed_2)
		{
			*right++ = i;
			v->spl_nright++;
			continue;
		}

		/* okay, which page needs least enlargement? */
		if (i == maxoff)
			item_1 = itup;
		else
			item_1 = (IndexTuple) PageGetItem(page, PageGetItemId(page, i));

		datum_alpha = ((char *) item_1) + sizeof(IndexTupleData);
		union_dl = (char *) (*fmgr_faddr(&rtstate->unionFn)) (datum_l, datum_alpha);
		union_dr = (char *) (*fmgr_faddr(&rtstate->unionFn)) (datum_r, datum_alpha);
		(*fmgr_faddr(&rtstate->sizeFn)) (union_dl, &size_alpha);
		(*fmgr_faddr(&rtstate->sizeFn)) (union_dr, &size_beta);

		/* pick which page to add it to */
		if (size_alpha - size_l < size_beta - size_r)
		{
			pfree(datum_l);
			pfree(union_dr);
			datum_l = union_dl;
			size_l = size_alpha;
			*left++ = i;
			v->spl_nleft++;
		}
		else
		{
			pfree(datum_r);
			pfree(union_dl);
			datum_r = union_dr;
			size_r = size_alpha;
			*right++ = i;
			v->spl_nright++;
		}
	}
	*left = *right = FirstOffsetNumber; /* sentinel value, see dosplit() */

	v->spl_ldatum = datum_l;
	v->spl_rdatum = datum_r;
}

static void
RTInitBuffer(Buffer b, uint32 f)
{
	RTreePageOpaque opaque;
	Page		page;
	Size		pageSize;

	pageSize = BufferGetPageSize(b);

	page = BufferGetPage(b);
	MemSet(page, 0, (int) pageSize);
	PageInit(page, pageSize, sizeof(RTreePageOpaqueData));

	opaque = (RTreePageOpaque) PageGetSpecialPointer(page);
	opaque->flags = f;
}

static OffsetNumber
choose(Relation r, Page p, IndexTuple it, RTSTATE *rtstate)
{
	OffsetNumber maxoff;
	OffsetNumber i;
	char	   *ud,
			   *id;
	char	   *datum;
	float		usize,
				dsize;
	OffsetNumber which;
	float		which_grow;

	id = ((char *) it) + sizeof(IndexTupleData);
	maxoff = PageGetMaxOffsetNumber(p);
	which_grow = -1.0;
	which = -1;

	for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
	{
		datum = (char *) PageGetItem(p, PageGetItemId(p, i));
		datum += sizeof(IndexTupleData);
		(*fmgr_faddr(&rtstate->sizeFn)) (datum, &dsize);
		ud = (char *) (*fmgr_faddr(&rtstate->unionFn)) (datum, id);
		(*fmgr_faddr(&rtstate->sizeFn)) (ud, &usize);
		pfree(ud);
		if (which_grow < 0 || usize - dsize < which_grow)
		{
			which = i;
			which_grow = usize - dsize;
			if (which_grow == 0)
				break;
		}
	}

	return which;
}

static int
nospace(Page p, IndexTuple it)
{
	return PageGetFreeSpace(p) < IndexTupleSize(it);
}

void
freestack(RTSTACK *s)
{
	RTSTACK    *p;

	while (s != (RTSTACK *) NULL)
	{
		p = s->rts_parent;
		pfree(s);
		s = p;
	}
}

char *
rtdelete(Relation r, ItemPointer tid)
{
	BlockNumber blkno;
	OffsetNumber offnum;
	Buffer		buf;
	Page		page;

	/*
	 * Notes in ExecUtils:ExecOpenIndices() Also note that only vacuum
	 * deletes index tuples now...
	 *
	 * RelationSetLockForWrite(r);
	 */

	blkno = ItemPointerGetBlockNumber(tid);
	offnum = ItemPointerGetOffsetNumber(tid);

	/* adjust any scans that will be affected by this deletion */
	rtadjscans(r, RTOP_DEL, blkno, offnum);

	/* delete the index tuple */
	buf = ReadBuffer(r, blkno);
	page = BufferGetPage(buf);

	PageIndexTupleDelete(page, offnum);

	WriteBuffer(buf);

	return (char *) NULL;
}

static void
initRtstate(RTSTATE *rtstate, Relation index)
{
	RegProcedure union_proc,
				size_proc,
				inter_proc;

	union_proc = index_getprocid(index, 1, RT_UNION_PROC);
	size_proc = index_getprocid(index, 1, RT_SIZE_PROC);
	inter_proc = index_getprocid(index, 1, RT_INTER_PROC);
	fmgr_info(union_proc, &rtstate->unionFn);
	fmgr_info(size_proc, &rtstate->sizeFn);
	fmgr_info(inter_proc, &rtstate->interFn);
	return;
}

#ifdef RTDEBUG

void
_rtdump(Relation r)
{
	Buffer		buf;
	Page		page;
	OffsetNumber offnum,
				maxoff;
	BlockNumber blkno;
	BlockNumber nblocks;
	RTreePageOpaque po;
	IndexTuple	itup;
	BlockNumber itblkno;
	OffsetNumber itoffno;
	char	   *datum;
	char	   *itkey;

	nblocks = RelationGetNumberOfBlocks(r);
	for (blkno = 0; blkno < nblocks; blkno++)
	{
		buf = ReadBuffer(r, blkno);
		page = BufferGetPage(buf);
		po = (RTreePageOpaque) PageGetSpecialPointer(page);
		maxoff = PageGetMaxOffsetNumber(page);
		printf("Page %d maxoff %d <%s>\n", blkno, maxoff,
			   (po->flags & F_LEAF ? "LEAF" : "INTERNAL"));

		if (PageIsEmpty(page))
		{
			ReleaseBuffer(buf);
			continue;
		}

		for (offnum = FirstOffsetNumber;
			 offnum <= maxoff;
			 offnum = OffsetNumberNext(offnum))
		{
			itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, offnum));
			itblkno = ItemPointerGetBlockNumber(&(itup->t_tid));
			itoffno = ItemPointerGetOffsetNumber(&(itup->t_tid));
			datum = ((char *) itup);
			datum += sizeof(IndexTupleData);
			itkey = (char *) box_out((BOX *) datum);
			printf("\t[%d] size %d heap <%d,%d> key:%s\n",
				   offnum, IndexTupleSize(itup), itblkno, itoffno, itkey);
			pfree(itkey);
		}

		ReleaseBuffer(buf);
	}
}

#endif	 /* defined RTDEBUG */