read0read.ic
上传用户:romrleung
上传日期:2022-05-23
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文件大小:2k
- /******************************************************
- Cursor read
- (c) 1997 Innobase Oy
- Created 2/16/1997 Heikki Tuuri
- *******************************************************/
- /*************************************************************************
- Gets the nth trx id in a read view. */
- UNIV_INLINE
- dulint
- read_view_get_nth_trx_id(
- /*=====================*/
- /* out: trx id */
- read_view_t* view, /* in: read view */
- ulint n) /* in: position */
- {
- ut_ad(n < view->n_trx_ids);
- return(*(view->trx_ids + n));
- }
- /*************************************************************************
- Sets the nth trx id in a read view. */
- UNIV_INLINE
- void
- read_view_set_nth_trx_id(
- /*=====================*/
- read_view_t* view, /* in: read view */
- ulint n, /* in: position */
- dulint trx_id) /* in: trx id to set */
- {
- ut_ad(n < view->n_trx_ids);
- *(view->trx_ids + n) = trx_id;
- }
- /*************************************************************************
- Checks if a read view sees the specified transaction. */
- UNIV_INLINE
- ibool
- read_view_sees_trx_id(
- /*==================*/
- /* out: TRUE if sees */
- read_view_t* view, /* in: read view */
- dulint trx_id) /* in: trx id */
- {
- ulint n_ids;
- int cmp;
- ulint i;
-
- if (ut_dulint_cmp(trx_id, view->up_limit_id) < 0) {
- return(TRUE);
- }
- if (ut_dulint_cmp(trx_id, view->low_limit_id) >= 0) {
- return(FALSE);
- }
- /* We go through the trx ids in the array smallest first: this order
- may save CPU time, because if there was a very long running
- transaction in the trx id array, its trx id is looked at first, and
- the first two comparisons may well decide the visibility of trx_id. */
- n_ids = view->n_trx_ids;
- for (i = 0; i < n_ids; i++) {
- cmp = ut_dulint_cmp(trx_id,
- read_view_get_nth_trx_id(view, n_ids - i - 1));
- if (0 == cmp) {
- return(FALSE);
- } else if (cmp < 0) {
- return(TRUE);
- }
- }
-
- return(TRUE);
- }