nbtree.c

关系型数据库 Postgresql 6.5.2

	itup->t_tid = *ht_ctid;

	/*
	 * See comments in btbuild.
	 *
	 * if (itup->t_info & INDEX_NULL_MASK) return (InsertIndexResult) NULL;
	 */

	btitem = _bt_formitem(itup);

	res = _bt_doinsert(rel, btitem,
					   IndexIsUnique(RelationGetRelid(rel)), heapRel);

	pfree(btitem);
	pfree(itup);

	return res;
}

/*
 *	btgettuple() -- Get the next tuple in the scan.
 */
char *
btgettuple(IndexScanDesc scan, ScanDirection dir)
{
	RetrieveIndexResult res;

	/*
	 * 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.
	 */

	if (ItemPointerIsValid(&(scan->currentItemData)))
	{

		/*
		 * Restore scan position using heap TID returned by previous call
		 * to btgettuple(). _bt_restscan() locks buffer.
		 */
		_bt_restscan(scan);
		res = _bt_next(scan, dir);
	}
	else
		res = _bt_first(scan, dir);

	/*
	 * Save heap TID to use it in _bt_restscan. Unlock buffer before
	 * leaving index !
	 */
	if (res)
	{
		((BTScanOpaque) scan->opaque)->curHeapIptr = res->heap_iptr;
		LockBuffer(((BTScanOpaque) scan->opaque)->btso_curbuf, BUFFER_LOCK_UNLOCK);
	}

	return (char *) res;
}

/*
 *	btbeginscan() -- start a scan on a btree index
 */
char *
btbeginscan(Relation rel, bool fromEnd, uint16 keysz, ScanKey scankey)
{
	IndexScanDesc scan;

	/* get the scan */
	scan = RelationGetIndexScan(rel, fromEnd, keysz, scankey);

	/* register scan in case we change pages it's using */
	_bt_regscan(scan);

	return (char *) scan;
}

/*
 *	btrescan() -- rescan an index relation
 */
void
btrescan(IndexScanDesc scan, bool fromEnd, ScanKey scankey)
{
	ItemPointer iptr;
	BTScanOpaque so;

	so = (BTScanOpaque) scan->opaque;

	/* we don't hold a read lock on the current page in the scan */
	if (ItemPointerIsValid(iptr = &(scan->currentItemData)))
	{
		ReleaseBuffer(so->btso_curbuf);
		so->btso_curbuf = InvalidBuffer;
		ItemPointerSetInvalid(iptr);
	}

	/* and we don't hold a read lock on the last marked item in the scan */
	if (ItemPointerIsValid(iptr = &(scan->currentMarkData)))
	{
		ReleaseBuffer(so->btso_mrkbuf);
		so->btso_mrkbuf = InvalidBuffer;
		ItemPointerSetInvalid(iptr);
	}

	if (so == NULL)				/* if called from btbeginscan */
	{
		so = (BTScanOpaque) palloc(sizeof(BTScanOpaqueData));
		so->btso_curbuf = so->btso_mrkbuf = InvalidBuffer;
		so->keyData = (ScanKey) NULL;
		if (scan->numberOfKeys > 0)
			so->keyData = (ScanKey) palloc(scan->numberOfKeys * sizeof(ScanKeyData));
		scan->opaque = so;
		scan->flags = 0x0;
	}

	/*
	 * Reset the scan keys. Note that keys ordering stuff moved to
	 * _bt_first.	   - vadim 05/05/97
	 */
	so->numberOfKeys = scan->numberOfKeys;
	if (scan->numberOfKeys > 0)
	{
		memmove(scan->keyData,
				scankey,
				scan->numberOfKeys * sizeof(ScanKeyData));
		memmove(so->keyData,
				scankey,
				so->numberOfKeys * sizeof(ScanKeyData));
	}

}

void
btmovescan(IndexScanDesc scan, Datum v)
{
	ItemPointer iptr;
	BTScanOpaque so;

	so = (BTScanOpaque) scan->opaque;

	/* we don't hold a read lock on the current page in the scan */
	if (ItemPointerIsValid(iptr = &(scan->currentItemData)))
	{
		ReleaseBuffer(so->btso_curbuf);
		so->btso_curbuf = InvalidBuffer;
		ItemPointerSetInvalid(iptr);
	}

/*	  scan->keyData[0].sk_argument = v; */
	so->keyData[0].sk_argument = v;
}

/*
 *	btendscan() -- close down a scan
 */
void
btendscan(IndexScanDesc scan)
{
	ItemPointer iptr;
	BTScanOpaque so;

	so = (BTScanOpaque) scan->opaque;

	/* we don't hold any read locks */
	if (ItemPointerIsValid(iptr = &(scan->currentItemData)))
	{
		if (BufferIsValid(so->btso_curbuf))
			ReleaseBuffer(so->btso_curbuf);
		so->btso_curbuf = InvalidBuffer;
		ItemPointerSetInvalid(iptr);
	}

	if (ItemPointerIsValid(iptr = &(scan->currentMarkData)))
	{
		if (BufferIsValid(so->btso_mrkbuf))
			ReleaseBuffer(so->btso_mrkbuf);
		so->btso_mrkbuf = InvalidBuffer;
		ItemPointerSetInvalid(iptr);
	}

	if (so->keyData != (ScanKey) NULL)
		pfree(so->keyData);
	pfree(so);

	_bt_dropscan(scan);
}

/*
 *	btmarkpos() -- save current scan position
 */
void
btmarkpos(IndexScanDesc scan)
{
	ItemPointer iptr;
	BTScanOpaque so;

	so = (BTScanOpaque) scan->opaque;

	/* we don't hold any read locks */
	if (ItemPointerIsValid(iptr = &(scan->currentMarkData)))
	{
		ReleaseBuffer(so->btso_mrkbuf);
		so->btso_mrkbuf = InvalidBuffer;
		ItemPointerSetInvalid(iptr);
	}

	/* bump pin on current buffer */
	if (ItemPointerIsValid(&(scan->currentItemData)))
	{
		so->btso_mrkbuf = ReadBuffer(scan->relation,
								  BufferGetBlockNumber(so->btso_curbuf));
		scan->currentMarkData = scan->currentItemData;
		so->mrkHeapIptr = so->curHeapIptr;
	}
}

/*
 *	btrestrpos() -- restore scan to last saved position
 */
void
btrestrpos(IndexScanDesc scan)
{
	ItemPointer iptr;
	BTScanOpaque so;

	so = (BTScanOpaque) scan->opaque;

	/* we don't hold any read locks */
	if (ItemPointerIsValid(iptr = &(scan->currentItemData)))
	{
		ReleaseBuffer(so->btso_curbuf);
		so->btso_curbuf = InvalidBuffer;
		ItemPointerSetInvalid(iptr);
	}

	/* bump pin on marked buffer */
	if (ItemPointerIsValid(&(scan->currentMarkData)))
	{
		so->btso_curbuf = ReadBuffer(scan->relation,
								  BufferGetBlockNumber(so->btso_mrkbuf));

		scan->currentItemData = scan->currentMarkData;
		so->curHeapIptr = so->mrkHeapIptr;
	}
}

/* stubs */
void
btdelete(Relation rel, ItemPointer tid)
{
	/* adjust any active scans that will be affected by this deletion */
	_bt_adjscans(rel, tid);

	/* delete the data from the page */
	_bt_pagedel(rel, tid);
}

static void
_bt_restscan(IndexScanDesc scan)
{
	Relation	rel = scan->relation;
	BTScanOpaque so = (BTScanOpaque) scan->opaque;
	Buffer		buf = so->btso_curbuf;
	Page		page;
	ItemPointer current = &(scan->currentItemData);
	OffsetNumber offnum = ItemPointerGetOffsetNumber(current),
				maxoff;
	BTPageOpaque opaque;
	ItemPointerData target = so->curHeapIptr;
	BTItem		item;
	BlockNumber blkno;

	LockBuffer(buf, BT_READ);		/* lock buffer first! */
	page = BufferGetPage(buf);
	maxoff = PageGetMaxOffsetNumber(page);
	opaque = (BTPageOpaque) PageGetSpecialPointer(page);

	/*
	 * We use this as flag when first index tuple on page is deleted but
	 * we do not move left (this would slowdown vacuum) - so we set
	 * current->ip_posid before first index tuple on the current page
	 * (_bt_step will move it right)...
	 */
	if (!ItemPointerIsValid(&target))
	{
		ItemPointerSetOffsetNumber(&(scan->currentItemData),
		   OffsetNumberPrev(P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY));
		return;
	}

	if (maxoff >= offnum)
	{

		/*
		 * if the item is where we left it or has just moved right on this
		 * page, we're done
		 */
		for (;
			 offnum <= maxoff;
			 offnum = OffsetNumberNext(offnum))
		{
			item = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
			if (item->bti_itup.t_tid.ip_blkid.bi_hi == \
				target.ip_blkid.bi_hi && \
				item->bti_itup.t_tid.ip_blkid.bi_lo == \
				target.ip_blkid.bi_lo && \
				item->bti_itup.t_tid.ip_posid == target.ip_posid)
			{
				current->ip_posid = offnum;
				return;
			}
		}
	}

	/*
	 * By here, the item we're looking for moved right at least one page
	 */
	for (;;)
	{
		if (P_RIGHTMOST(opaque))
			elog(FATAL, "_bt_restscan: my bits moved right off the end of the world!");

		blkno = opaque->btpo_next;
		_bt_relbuf(rel, buf, BT_READ);
		buf = _bt_getbuf(rel, blkno, BT_READ);
		page = BufferGetPage(buf);
		maxoff = PageGetMaxOffsetNumber(page);
		opaque = (BTPageOpaque) PageGetSpecialPointer(page);

		/* see if it's on this page */
		for (offnum = P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY;
			 offnum <= maxoff;
			 offnum = OffsetNumberNext(offnum))
		{
			item = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
			if (item->bti_itup.t_tid.ip_blkid.bi_hi == \
				target.ip_blkid.bi_hi && \
				item->bti_itup.t_tid.ip_blkid.bi_lo == \
				target.ip_blkid.bi_lo && \
				item->bti_itup.t_tid.ip_posid == target.ip_posid)
			{
				ItemPointerSet(current, blkno, offnum);
				so->btso_curbuf = buf;
				return;
			}
		}
	}
}