Example #1
0
/*
 * __cursor_var_next --
 *	Move to the next, variable-length column-store item.
 */
static inline int
__cursor_var_next(WT_CURSOR_BTREE *cbt, bool newpage)
{
	WT_CELL *cell;
	WT_CELL_UNPACK unpack;
	WT_COL *cip;
	WT_INSERT *ins;
	WT_PAGE *page;
	WT_SESSION_IMPL *session;
	WT_UPDATE *upd;
	uint64_t rle, rle_start;

	session = (WT_SESSION_IMPL *)cbt->iface.session;
	page = cbt->ref->page;

	rle_start = 0;			/* -Werror=maybe-uninitialized */

	/* Initialize for each new page. */
	if (newpage) {
		cbt->last_standard_recno = __col_var_last_recno(cbt->ref);
		if (cbt->last_standard_recno == 0)
			return (WT_NOTFOUND);
		__cursor_set_recno(cbt, cbt->ref->ref_recno);
		cbt->cip_saved = NULL;
		goto new_page;
	}

	/* Move to the next entry and return the item. */
	for (;;) {
		if (cbt->recno >= cbt->last_standard_recno)
			return (WT_NOTFOUND);
		__cursor_set_recno(cbt, cbt->recno + 1);

new_page:	/* Find the matching WT_COL slot. */
		if ((cip =
		    __col_var_search(cbt->ref, cbt->recno, &rle_start)) == NULL)
			return (WT_NOTFOUND);
		cbt->slot = WT_COL_SLOT(page, cip);

		/* Check any insert list for a matching record. */
		cbt->ins_head = WT_COL_UPDATE_SLOT(page, cbt->slot);
		cbt->ins = __col_insert_search_match(cbt->ins_head, cbt->recno);
		upd = cbt->ins == NULL ?
		    NULL : __wt_txn_read(session, cbt->ins->upd);
		if (upd != NULL) {
			if (upd->type == WT_UPDATE_DELETED) {
				if (__wt_txn_upd_visible_all(session, upd))
					++cbt->page_deleted_count;
				continue;
			}
			return (__wt_value_return(session, cbt, upd));
		}

		/*
		 * If we're at the same slot as the last reference and there's
		 * no matching insert list item, re-use the return information
		 * (so encoded items with large repeat counts aren't repeatedly
		 * decoded).  Otherwise, unpack the cell and build the return
		 * information.
		 */
		if (cbt->cip_saved != cip) {
			if ((cell = WT_COL_PTR(page, cip)) == NULL)
				continue;
			__wt_cell_unpack(cell, &unpack);
			if (unpack.type == WT_CELL_DEL) {
				if ((rle = __wt_cell_rle(&unpack)) == 1)
					continue;

				/*
				 * There can be huge gaps in the variable-length
				 * column-store name space appearing as deleted
				 * records. If more than one deleted record, do
				 * the work of finding the next record to return
				 * instead of looping through the records.
				 *
				 * First, find the smallest record in the update
				 * list that's larger than the current record.
				 */
				ins = __col_insert_search_gt(
				    cbt->ins_head, cbt->recno);

				/*
				 * Second, for records with RLEs greater than 1,
				 * the above call to __col_var_search located
				 * this record in the page's list of repeating
				 * records, and returned the starting record.
				 * The starting record plus the RLE is the
				 * record to which we could skip, if there was
				 * no smaller record in the update list.
				 */
				cbt->recno = rle_start + rle;
				if (ins != NULL &&
				    WT_INSERT_RECNO(ins) < cbt->recno)
					cbt->recno = WT_INSERT_RECNO(ins);

				/* Adjust for the outer loop increment. */
				--cbt->recno;
				continue;
			}
			WT_RET(__wt_page_cell_data_ref(
			    session, page, &unpack, cbt->tmp));

			cbt->cip_saved = cip;
		}
		cbt->iface.value.data = cbt->tmp->data;
		cbt->iface.value.size = cbt->tmp->size;
		return (0);
	}
	/* NOTREACHED */
}
Example #2
0
/*移向下条variable-length column-store 记录*/
static inline int __cursor_var_next(WT_CURSOR_BTREE* cbt, int newpage)
{
	WT_CELL *cell;
	WT_CELL_UNPACK unpack;
	WT_COL *cip;
	WT_ITEM *val;
	WT_INSERT *ins;
	WT_PAGE *page;
	WT_SESSION_IMPL *session;
	WT_UPDATE *upd;
	uint64_t rle, rle_start;

	session = (WT_SESSION_IMPL *)cbt->iface.session;
	page = cbt->ref->page;
	val = &cbt->iface.value;

	rle_start = 0;			/* -Werror=maybe-uninitialized */

	if (newpage){
		cbt->last_standard_recno = __col_var_last_recno(page);
		if (cbt->last_standard_recno == 0)
			return (WT_NOTFOUND);
		__cursor_set_recno(cbt, page->pg_var_recno);
		goto new_page;
	}

	for (;;){
		if (cbt->recno >= cbt->last_standard_recno)
			return (WT_NOTFOUND);
		__cursor_set_recno(cbt, cbt->recno + 1);

	new_page:
		/*定位到recno对应的WT_COL slot*/
		if ((cip = __col_var_search(page, cbt->recno, &rle_start)) == NULL)
			return (WT_NOTFOUND);
		cbt->slot = WT_COL_SLOT(page, cip);

		/*读取内容值*/
		cbt->ins_head = WT_COL_UPDATE_SLOT(page, cbt->slot);
		cbt->ins = __col_insert_search_match(cbt->ins_head, cbt->recno);
		upd = cbt->ins == NULL ? NULL : __wt_txn_read(session, cbt->ins->upd);
		if (upd != NULL) {
			if (WT_UPDATE_DELETED_ISSET(upd)) {
				++cbt->page_deleted_count;
				continue;
			}

			val->data = WT_UPDATE_DATA(upd);
			val->size = upd->size;
			return (0);
		}

		/*
		* If we're at the same slot as the last reference and there's
		* no matching insert list item, re-use the return information
		* (so encoded items with large repeat counts aren't repeatedly
		* decoded).  Otherwise, unpack the cell and build the return
		* information.
		* upd == NULL, 记录可能被删除放入到了insert列表中,slot可能被重用了,那么需要进行cell unpack取值
		*/

		if (cbt->cip_saved != cip) {
			if ((cell = WT_COL_PTR(page, cip)) == NULL)
				continue;
			__wt_cell_unpack(cell, &unpack);
			if (unpack.type == WT_CELL_DEL) {
				if ((rle = __wt_cell_rle(&unpack)) == 1)
					continue;

				/*定位到修改列表中的记录*/
				ins = __col_insert_search_gt(cbt->ins_head, cbt->recno);
				cbt->recno = rle_start + rle;
				if (ins != NULL && WT_INSERT_RECNO(ins) < cbt->recno)
					cbt->recno = WT_INSERT_RECNO(ins);

				/* Adjust for the outer loop increment. */
				--cbt->recno;
				continue;
			}

			/*取出cell中的值到tmp中*/
			WT_RET(__wt_page_cell_data_ref(session, page, &unpack, &cbt->tmp));
			cbt->cip_saved = cip;
		}
		val->data = cbt->tmp.data;
		val->size = cbt->tmp.size;
		return 0;
	}
}