gist.c

postgresql8.3.4源码,开源数据库

	 * ready to recheck path in a bad case... We remember, that page->lsn
	 * should never be invalid.
	 */
	for (;;)
	{
		if (XLogRecPtrIsInvalid(state->stack->lsn))
			state->stack->buffer = ReadBuffer(state->r, state->stack->blkno);
		LockBuffer(state->stack->buffer, GIST_SHARE);
		gistcheckpage(state->r, state->stack->buffer);

		state->stack->page = (Page) BufferGetPage(state->stack->buffer);
		opaque = GistPageGetOpaque(state->stack->page);

		state->stack->lsn = PageGetLSN(state->stack->page);
		Assert(state->r->rd_istemp || !XLogRecPtrIsInvalid(state->stack->lsn));

		if (state->stack->blkno != GIST_ROOT_BLKNO &&
			XLByteLT(state->stack->parent->lsn, opaque->nsn))
		{
			/*
			 * caused split non-root page is detected, go up to parent to
			 * choose best child
			 */
			UnlockReleaseBuffer(state->stack->buffer);
			state->stack = state->stack->parent;
			continue;
		}

		if (!GistPageIsLeaf(state->stack->page))
		{
			/*
			 * This is an internal page, so continue to walk down the tree. We
			 * find the child node that has the minimum insertion penalty and
			 * recursively invoke ourselves to modify that node. Once the
			 * recursive call returns, we may need to adjust the parent node
			 * for two reasons: the child node split, or the key in this node
			 * needs to be adjusted for the newly inserted key below us.
			 */
			GISTInsertStack *item = (GISTInsertStack *) palloc0(sizeof(GISTInsertStack));

			state->stack->childoffnum = gistchoose(state->r, state->stack->page, state->itup[0], giststate);

			iid = PageGetItemId(state->stack->page, state->stack->childoffnum);
			idxtuple = (IndexTuple) PageGetItem(state->stack->page, iid);
			item->blkno = ItemPointerGetBlockNumber(&(idxtuple->t_tid));
			LockBuffer(state->stack->buffer, GIST_UNLOCK);

			item->parent = state->stack;
			item->child = NULL;
			if (state->stack)
				state->stack->child = item;
			state->stack = item;
		}
		else
		{
			/* be carefull, during unlock/lock page may be changed... */
			LockBuffer(state->stack->buffer, GIST_UNLOCK);
			LockBuffer(state->stack->buffer, GIST_EXCLUSIVE);
			state->stack->page = (Page) BufferGetPage(state->stack->buffer);
			opaque = GistPageGetOpaque(state->stack->page);

			if (state->stack->blkno == GIST_ROOT_BLKNO)
			{
				/*
				 * the only page can become inner instead of leaf is a root
				 * page, so for root we should recheck it
				 */
				if (!GistPageIsLeaf(state->stack->page))
				{
					/*
					 * very rarely situation: during unlock/lock index with
					 * number of pages = 1 was increased
					 */
					LockBuffer(state->stack->buffer, GIST_UNLOCK);
					continue;
				}

				/*
				 * we don't need to check root split, because checking
				 * leaf/inner is enough to recognize split for root
				 */

			}
			else if (XLByteLT(state->stack->parent->lsn, opaque->nsn))
			{
				/*
				 * detecting split during unlock/lock, so we should find
				 * better child on parent
				 */

				/* forget buffer */
				UnlockReleaseBuffer(state->stack->buffer);

				state->stack = state->stack->parent;
				continue;
			}

			state->stack->lsn = PageGetLSN(state->stack->page);

			/* ok we found a leaf page and it X-locked */
			break;
		}
	}

	/* now state->stack->(page, buffer and blkno) points to leaf page */
}

/*
 * Traverse the tree to find path from root page to specified "child" block.
 *
 * returns from the beginning of closest parent;
 *
 * To prevent deadlocks, this should lock only one page simultaneously.
 */
GISTInsertStack *
gistFindPath(Relation r, BlockNumber child)
{
	Page		page;
	Buffer		buffer;
	OffsetNumber i,
				maxoff;
	ItemId		iid;
	IndexTuple	idxtuple;
	GISTInsertStack *top,
			   *tail,
			   *ptr;
	BlockNumber blkno;

	top = tail = (GISTInsertStack *) palloc0(sizeof(GISTInsertStack));
	top->blkno = GIST_ROOT_BLKNO;

	while (top && top->blkno != child)
	{
		buffer = ReadBuffer(r, top->blkno);
		LockBuffer(buffer, GIST_SHARE);
		gistcheckpage(r, buffer);
		page = (Page) BufferGetPage(buffer);

		if (GistPageIsLeaf(page))
		{
			/* we can safety go away, follows only leaf pages */
			UnlockReleaseBuffer(buffer);
			return NULL;
		}

		top->lsn = PageGetLSN(page);

		if (top->parent && XLByteLT(top->parent->lsn, GistPageGetOpaque(page)->nsn) &&
			GistPageGetOpaque(page)->rightlink != InvalidBlockNumber /* sanity check */ )
		{
			/* page splited while we thinking of... */
			ptr = (GISTInsertStack *) palloc0(sizeof(GISTInsertStack));
			ptr->blkno = GistPageGetOpaque(page)->rightlink;
			ptr->childoffnum = InvalidOffsetNumber;
			ptr->parent = top;
			ptr->next = NULL;
			tail->next = ptr;
			tail = ptr;
		}

		maxoff = PageGetMaxOffsetNumber(page);

		for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
		{
			iid = PageGetItemId(page, i);
			idxtuple = (IndexTuple) PageGetItem(page, iid);
			blkno = ItemPointerGetBlockNumber(&(idxtuple->t_tid));
			if (blkno == child)
			{
				OffsetNumber poff = InvalidOffsetNumber;

				/* make childs links */
				ptr = top;
				while (ptr->parent)
				{
					/* set child link */
					ptr->parent->child = ptr;
					/* move childoffnum.. */
					if (ptr == top)
					{
						/* first iteration */
						poff = ptr->parent->childoffnum;
						ptr->parent->childoffnum = ptr->childoffnum;
					}
					else
					{
						OffsetNumber tmp = ptr->parent->childoffnum;

						ptr->parent->childoffnum = poff;
						poff = tmp;
					}
					ptr = ptr->parent;
				}
				top->childoffnum = i;
				UnlockReleaseBuffer(buffer);
				return top;
			}
			else
			{
				/* Install next inner page to the end of stack */
				ptr = (GISTInsertStack *) palloc0(sizeof(GISTInsertStack));
				ptr->blkno = blkno;
				ptr->childoffnum = i;	/* set offsetnumber of child to child
										 * !!! */
				ptr->parent = top;
				ptr->next = NULL;
				tail->next = ptr;
				tail = ptr;
			}
		}

		UnlockReleaseBuffer(buffer);
		top = top->next;
	}

	return NULL;
}


/*
 * Returns X-locked parent of stack page
 */

static void
gistFindCorrectParent(Relation r, GISTInsertStack *child)
{
	GISTInsertStack *parent = child->parent;

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

	/* here we don't need to distinguish between split and page update */
	if (parent->childoffnum == InvalidOffsetNumber || !XLByteEQ(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 */
					parent->childoffnum = i;
					return;
				}
			}

			parent->blkno = GistPageGetOpaque(parent->page)->rightlink;
			UnlockReleaseBuffer(parent->buffer);
			if (parent->blkno == InvalidBlockNumber)

				/*
				 * end of chain and still didn't found parent, It's 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);
		Assert(ptr != NULL);

		/* 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;
		parent->child = child;

		/* make recursive call to normal processing */
		gistFindCorrectParent(r, child);
	}

	return;
}

void
gistmakedeal(GISTInsertState *state, GISTSTATE *giststate)
{
	int			is_splitted;
	ItemId		iid;
	IndexTuple	oldtup,
				newtup;

	/* walk up */
	while (true)
	{
		/*
		 * After this call: 1. if child page was splited, then itup contains
		 * keys for each page 2. if  child page wasn't splited, then itup
		 * contains additional for adjustment of current key
		 */

		if (state->stack->parent)
		{
			/*
			 * X-lock parent page before proceed child, gistFindCorrectParent
			 * should find and lock it
			 */
			gistFindCorrectParent(state->r, state->stack);
		}
		is_splitted = gistplacetopage(state, giststate);

		/* parent locked above, so release child buffer */
		UnlockReleaseBuffer(state->stack->buffer);

		/* pop parent page from stack */
		state->stack = state->stack->parent;

		/* stack is void */
		if (!state->stack)
			break;

		/*
		 * child did not split, so we can check is it needed to update parent
		 * tuple
		 */
		if (!is_splitted)
		{
			/* parent's tuple */
			iid = PageGetItemId(state->stack->page, state->stack->childoffnum);
			oldtup = (IndexTuple) PageGetItem(state->stack->page, iid);
			newtup = gistgetadjusted(state->r, oldtup, state->itup[0], giststate);

			if (!newtup)
			{					/* not need to update key */
				LockBuffer(state->stack->buffer, GIST_UNLOCK);
				break;
			}

			state->itup[0] = newtup;
		}
	}							/* while */

	/* release all parent buffers */
	while (state->stack)
	{
		ReleaseBuffer(state->stack->buffer);
		state->stack = state->stack->parent;
	}

	/* say to xlog that insert is completed */
	if (state->needInsertComplete && !state->r->rd_istemp)
		gistxlogInsertCompletion(state->r->rd_node, &(state->key), 1);
}

/*
 * gistSplit -- split a page in the tree and fill struct
 * used for XLOG and real writes buffers. Function is recursive, ie
 * it will split page until keys will fit in every page.
 */
SplitedPageLayout *
gistSplit(Relation r,
		  Page page,
		  IndexTuple *itup,		/* contains compressed entry */
		  int len,
		  GISTSTATE *giststate)
{
	IndexTuple *lvectup,
			   *rvectup;
	GistSplitVector v;
	GistEntryVector *entryvec;
	int			i;
	SplitedPageLayout *res = NULL;

	/* generate the item array */
	entryvec = palloc(GEVHDRSZ + (len + 1) * sizeof(GISTENTRY));
	entryvec->n = len + 1;

	memset(v.spl_lisnull, TRUE, sizeof(bool) * giststate->tupdesc->natts);
	memset(v.spl_risnull, TRUE, sizeof(bool) * giststate->tupdesc->natts);
	gistSplitByKey(r, page, itup, len, giststate,
				   &v, entryvec, 0);

	/* form left and right vector */
	lvectup = (IndexTuple *) palloc(sizeof(IndexTuple) * (len + 1));
	rvectup = (IndexTuple *) palloc(sizeof(IndexTuple) * (len + 1));

	for (i = 0; i < v.splitVector.spl_nleft; i++)
		lvectup[i] = itup[v.splitVector.spl_left[i] - 1];

	for (i = 0; i < v.splitVector.spl_nright; i++)
		rvectup[i] = itup[v.splitVector.spl_right[i] - 1];

	/* finalize splitting (may need another split) */
	if (!gistfitpage(rvectup, v.splitVector.spl_nright))
	{
		res = gistSplit(r, page, rvectup, v.splitVector.spl_nright, giststate);
	}
	else
	{
		ROTATEDIST(res);
		res->block.num = v.splitVector.spl_nright;
		res->list = gistfillitupvec(rvectup, v.splitVector.spl_nright, &(res->lenlist));
		res->itup = (v.spl_rightvalid) ? gistFormTuple(giststate, r, v.spl_rattr, v.spl_risnull, false)
			: gist_form_invalid_tuple(GIST_ROOT_BLKNO);
	}

	if (!gistfitpage(lvectup, v.splitVector.spl_nleft))
	{
		SplitedPageLayout *resptr,
				   *subres;

		resptr = subres = gistSplit(r, page, lvectup, v.splitVector.spl_nleft, giststate);

		/* install on list's tail */
		while (resptr->next)
			resptr = resptr->next;

		resptr->next = res;
		res = subres;
	}
	else
	{
		ROTATEDIST(res);
		res->block.num = v.splitVector.spl_nleft;
		res->list = gistfillitupvec(lvectup, v.splitVector.spl_nleft, &(res->lenlist));
		res->itup = (v.spl_leftvalid) ? gistFormTuple(giststate, r, v.spl_lattr, v.spl_lisnull, false)
			: gist_form_invalid_tuple(GIST_ROOT_BLKNO);
	}

	return res;
}

/*
 * buffer must be pinned and locked by caller
 */
void
gistnewroot(Relation r, Buffer buffer, IndexTuple *itup, int len, ItemPointer key)
{
	Page		page;

	Assert(BufferGetBlockNumber(buffer) == GIST_ROOT_BLKNO);
	page = BufferGetPage(buffer);

	START_CRIT_SECTION();

	GISTInitBuffer(buffer, 0);
	gistfillbuffer(r, page, itup, len, FirstOffsetNumber);

	MarkBufferDirty(buffer);

	if (!r->rd_istemp)
	{
		XLogRecPtr	recptr;
		XLogRecData *rdata;

		rdata = formUpdateRdata(r->rd_node, buffer,
								NULL, 0,
								itup, len, key);

		recptr = XLogInsert(RM_GIST_ID, XLOG_GIST_NEW_ROOT, rdata);
		PageSetLSN(page, recptr);
		PageSetTLI(page, ThisTimeLineID);
	}
	else
		PageSetLSN(page, XLogRecPtrForTemp);

	END_CRIT_SECTION();
}

void
initGISTstate(GISTSTATE *giststate, Relation index)
{
	int			i;

	if (index->rd_att->natts > INDEX_MAX_KEYS)
		elog(ERROR, "numberOfAttributes %d > %d",
			 index->rd_att->natts, INDEX_MAX_KEYS);

	giststate->tupdesc = index->rd_att;

	for (i = 0; i < index->rd_att->natts; i++)
	{
		fmgr_info_copy(&(giststate->consistentFn[i]),
					   index_getprocinfo(index, i + 1, GIST_CONSISTENT_PROC),
					   CurrentMemoryContext);
		fmgr_info_copy(&(giststate->unionFn[i]),
					   index_getprocinfo(index, i + 1, GIST_UNION_PROC),
					   CurrentMemoryContext);
		fmgr_info_copy(&(giststate->compressFn[i]),
					   index_getprocinfo(index, i + 1, GIST_COMPRESS_PROC),
					   CurrentMemoryContext);
		fmgr_info_copy(&(giststate->decompressFn[i]),
					   index_getprocinfo(index, i + 1, GIST_DECOMPRESS_PROC),
					   CurrentMemoryContext);
		fmgr_info_copy(&(giststate->penaltyFn[i]),
					   index_getprocinfo(index, i + 1, GIST_PENALTY_PROC),
					   CurrentMemoryContext);
		fmgr_info_copy(&(giststate->picksplitFn[i]),
					   index_getprocinfo(index, i + 1, GIST_PICKSPLIT_PROC),
					   CurrentMemoryContext);
		fmgr_info_copy(&(giststate->equalFn[i]),
					   index_getprocinfo(index, i + 1, GIST_EQUAL_PROC),
					   CurrentMemoryContext);
	}
}

void
freeGISTstate(GISTSTATE *giststate)
{
	/* no work */
}