btr0cur.ic
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上传日期:2022-05-23
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文件大小:4k
- /******************************************************
- The index tree cursor
- (c) 1994-1996 Innobase Oy
- Created 10/16/1994 Heikki Tuuri
- *******************************************************/
- #include "btr0btr.h"
- /*************************************************************
- Returns the page cursor component of a tree cursor. */
- UNIV_INLINE
- page_cur_t*
- btr_cur_get_page_cur(
- /*=================*/
- /* out: pointer to page cursor component */
- btr_cur_t* cursor) /* in: tree cursor */
- {
- return(&(cursor->page_cur));
- }
- /*************************************************************
- Returns the record pointer of a tree cursor. */
- UNIV_INLINE
- rec_t*
- btr_cur_get_rec(
- /*============*/
- /* out: pointer to record */
- btr_cur_t* cursor) /* in: tree cursor */
- {
- return(page_cur_get_rec(&(cursor->page_cur)));
- }
- /*************************************************************
- Invalidates a tree cursor by setting record pointer to NULL. */
- UNIV_INLINE
- void
- btr_cur_invalidate(
- /*===============*/
- btr_cur_t* cursor) /* in: tree cursor */
- {
- page_cur_invalidate(&(cursor->page_cur));
- }
- /*************************************************************
- Returns the page of a tree cursor. */
- UNIV_INLINE
- page_t*
- btr_cur_get_page(
- /*=============*/
- /* out: pointer to page */
- btr_cur_t* cursor) /* in: tree cursor */
- {
- return(buf_frame_align(page_cur_get_rec(&(cursor->page_cur))));
- }
- /*************************************************************
- Returns the tree of a cursor. */
- UNIV_INLINE
- dict_tree_t*
- btr_cur_get_tree(
- /*=============*/
- /* out: tree */
- btr_cur_t* cursor) /* in: tree cursor */
- {
- return((cursor->index)->tree);
- }
- /*************************************************************
- Positions a tree cursor at a given record. */
- UNIV_INLINE
- void
- btr_cur_position(
- /*=============*/
- dict_index_t* index, /* in: index */
- rec_t* rec, /* in: record in tree */
- btr_cur_t* cursor) /* in: cursor */
- {
- page_cur_position(rec, btr_cur_get_page_cur(cursor));
- cursor->index = index;
- }
- /*************************************************************************
- Checks if compressing an index page where a btr cursor is placed makes
- sense. */
- UNIV_INLINE
- ibool
- btr_cur_compress_recommendation(
- /*============================*/
- /* out: TRUE if compression is recommended */
- btr_cur_t* cursor, /* in: btr cursor */
- mtr_t* mtr) /* in: mtr */
- {
- page_t* page;
-
- ut_ad(mtr_memo_contains(mtr, buf_block_align(
- btr_cur_get_page(cursor)),
- MTR_MEMO_PAGE_X_FIX));
- page = btr_cur_get_page(cursor);
- if ((page_get_data_size(page) < BTR_CUR_PAGE_COMPRESS_LIMIT)
- || ((btr_page_get_next(page, mtr) == FIL_NULL)
- && (btr_page_get_prev(page, mtr) == FIL_NULL))) {
- /* The page fillfactor has dropped below a predefined
- minimum value OR the level in the B-tree contains just
- one page: we recommend compression if this is not the
- root page. */
-
- if (dict_tree_get_page((cursor->index)->tree)
- == buf_frame_get_page_no(page)) {
- /* It is the root page */
- return(FALSE);
- }
- return(TRUE);
- }
- return(FALSE);
- }
- /*************************************************************************
- Checks if the record on which the cursor is placed can be deleted without
- making tree compression necessary (or, recommended). */
- UNIV_INLINE
- ibool
- btr_cur_can_delete_without_compress(
- /*================================*/
- /* out: TRUE if can be deleted without
- recommended compression */
- btr_cur_t* cursor, /* in: btr cursor */
- mtr_t* mtr) /* in: mtr */
- {
- ulint rec_size;
- page_t* page;
-
- ut_ad(mtr_memo_contains(mtr, buf_block_align(
- btr_cur_get_page(cursor)),
- MTR_MEMO_PAGE_X_FIX));
- rec_size = rec_get_size(btr_cur_get_rec(cursor));
- page = btr_cur_get_page(cursor);
- if ((page_get_data_size(page) - rec_size < BTR_CUR_PAGE_COMPRESS_LIMIT)
- || ((btr_page_get_next(page, mtr) == FIL_NULL)
- && (btr_page_get_prev(page, mtr) == FIL_NULL))
- || (page_get_n_recs(page) < 2)) {
- /* The page fillfactor will drop below a predefined
- minimum value, OR the level in the B-tree contains just
- one page, OR the page will become empty: we recommend
- compression if this is not the root page. */
-
- if (dict_tree_get_page((cursor->index)->tree)
- == buf_frame_get_page_no(page)) {
- /* It is the root page */
- return(TRUE);
- }
- return(FALSE);
- }
- return(TRUE);
- }