read0read.c
上传用户:romrleung
上传日期:2022-05-23
资源大小:18897k
文件大小:6k
- /******************************************************
- Cursor read
- (c) 1997 Innobase Oy
- Created 2/16/1997 Heikki Tuuri
- *******************************************************/
- #include "read0read.h"
- #ifdef UNIV_NONINL
- #include "read0read.ic"
- #endif
- #include "srv0srv.h"
- #include "trx0sys.h"
- /*************************************************************************
- Creates a read view object. */
- UNIV_INLINE
- read_view_t*
- read_view_create_low(
- /*=================*/
- /* out, own: read view struct */
- ulint n, /* in: number of cells in the trx_ids array */
- mem_heap_t* heap) /* in: memory heap from which allocated */
- {
- read_view_t* view;
- view = mem_heap_alloc(heap, sizeof(read_view_t));
- view->n_trx_ids = n;
- view->trx_ids = mem_heap_alloc(heap, n * sizeof(dulint));
- return(view);
- }
- /*************************************************************************
- Makes a copy of the oldest existing read view, with the exception that also
- the creating trx of the oldest view is set as not visible in the 'copied'
- view. Opens a new view if no views currently exist. The view must be closed
- with ..._close. This is used in purge. */
- read_view_t*
- read_view_oldest_copy_or_open_new(
- /*==============================*/
- /* out, own: read view struct */
- trx_t* cr_trx, /* in: creating transaction, or NULL */
- mem_heap_t* heap) /* in: memory heap from which allocated */
- {
- read_view_t* old_view;
- read_view_t* view_copy;
- ibool needs_insert = TRUE;
- ulint insert_done = 0;
- ulint n;
- ulint i;
- #ifdef UNIV_SYNC_DEBUG
- ut_ad(mutex_own(&kernel_mutex));
- #endif /* UNIV_SYNC_DEBUG */
- old_view = UT_LIST_GET_LAST(trx_sys->view_list);
- if (old_view == NULL) {
- return(read_view_open_now(cr_trx, heap));
- }
- n = old_view->n_trx_ids;
- if (old_view->creator) {
- n++;
- } else {
- needs_insert = FALSE;
- }
- view_copy = read_view_create_low(n, heap);
-
- /* Insert the id of the creator in the right place of the descending
- array of ids, if needs_insert is TRUE: */
- i = 0;
- while (i < n) {
- if (needs_insert
- && (i >= old_view->n_trx_ids
- || ut_dulint_cmp(old_view->creator->id,
- read_view_get_nth_trx_id(old_view, i))
- > 0)) {
- read_view_set_nth_trx_id(view_copy, i,
- old_view->creator->id);
- needs_insert = FALSE;
- insert_done = 1;
- } else {
- read_view_set_nth_trx_id(view_copy, i,
- read_view_get_nth_trx_id(old_view,
- i - insert_done));
- }
- i++;
- }
- view_copy->creator = cr_trx;
-
- view_copy->low_limit_no = old_view->low_limit_no;
- view_copy->low_limit_id = old_view->low_limit_id;
- view_copy->can_be_too_old = FALSE;
- if (n > 0) {
- /* The last active transaction has the smallest id: */
- view_copy->up_limit_id = read_view_get_nth_trx_id(
- view_copy, n - 1);
- } else {
- view_copy->up_limit_id = old_view->up_limit_id;
- }
- UT_LIST_ADD_LAST(view_list, trx_sys->view_list, view_copy);
- return(view_copy);
- }
- /*************************************************************************
- Opens a read view where exactly the transactions serialized before this
- point in time are seen in the view. */
- read_view_t*
- read_view_open_now(
- /*===============*/
- /* out, own: read view struct */
- trx_t* cr_trx, /* in: creating transaction, or NULL */
- mem_heap_t* heap) /* in: memory heap from which allocated */
- {
- read_view_t* view;
- trx_t* trx;
- ulint n;
- #ifdef UNIV_SYNC_DEBUG
- ut_ad(mutex_own(&kernel_mutex));
- #endif /* UNIV_SYNC_DEBUG */
- view = read_view_create_low(UT_LIST_GET_LEN(trx_sys->trx_list), heap);
- view->creator = cr_trx;
- /* No future transactions should be visible in the view */
- view->low_limit_no = trx_sys->max_trx_id;
- view->low_limit_id = view->low_limit_no;
- view->can_be_too_old = FALSE;
- n = 0;
- trx = UT_LIST_GET_FIRST(trx_sys->trx_list);
- /* No active transaction should be visible, except cr_trx */
- while (trx) {
- if (trx != cr_trx && trx->conc_state == TRX_ACTIVE) {
- read_view_set_nth_trx_id(view, n, trx->id);
-
- n++;
- /* NOTE that a transaction whose trx number is <
- trx_sys->max_trx_id can still be active, if it is
- in the middle of its commit! Note that when a
- transaction starts, we initialize trx->no to
- ut_dulint_max. */
-
- if (ut_dulint_cmp(view->low_limit_no, trx->no) > 0) {
- view->low_limit_no = trx->no;
- }
- }
- trx = UT_LIST_GET_NEXT(trx_list, trx);
- }
- view->n_trx_ids = n;
- if (n > 0) {
- /* The last active transaction has the smallest id: */
- view->up_limit_id = read_view_get_nth_trx_id(view, n - 1);
- } else {
- view->up_limit_id = view->low_limit_id;
- }
- UT_LIST_ADD_FIRST(view_list, trx_sys->view_list, view);
-
- return(view);
- }
- /*************************************************************************
- Closes a read view. */
- void
- read_view_close(
- /*============*/
- read_view_t* view) /* in: read view */
- {
- #ifdef UNIV_SYNC_DEBUG
- ut_ad(mutex_own(&kernel_mutex));
- #endif /* UNIV_SYNC_DEBUG */
- UT_LIST_REMOVE(view_list, trx_sys->view_list, view);
- }
- /*************************************************************************
- Closes a consistent read view for MySQL. This function is called at an SQL
- statement end if the trx isolation level is <= TRX_ISO_READ_COMMITTED. */
- void
- read_view_close_for_mysql(
- /*======================*/
- trx_t* trx) /* in: trx which has a read view */
- {
- ut_a(trx->read_view);
- mutex_enter(&kernel_mutex);
- read_view_close(trx->read_view);
- mem_heap_empty(trx->read_view_heap);
- trx->read_view = NULL;
- mutex_exit(&kernel_mutex);
- }
-
- /*************************************************************************
- Prints a read view to stderr. */
- void
- read_view_print(
- /*============*/
- read_view_t* view) /* in: read view */
- {
- ulint n_ids;
- ulint i;
-
- fprintf(stderr, "Read view low limit trx n:o %lu %lun",
- (ulong) ut_dulint_get_high(view->low_limit_no),
- (ulong) ut_dulint_get_low(view->low_limit_no));
- fprintf(stderr, "Read view up limit trx id %lu %lun",
- (ulong) ut_dulint_get_high(view->up_limit_id),
- (ulong) ut_dulint_get_low(view->up_limit_id));
- fprintf(stderr, "Read view low limit trx id %lu %lun",
- (ulong) ut_dulint_get_high(view->low_limit_id),
- (ulong) ut_dulint_get_low(view->low_limit_id));
- fprintf(stderr, "Read view individually stored trx ids:n");
- n_ids = view->n_trx_ids;
- for (i = 0; i < n_ids; i++) {
- fprintf(stderr, "Read view trx id %lu %lun",
- (ulong) ut_dulint_get_high(read_view_get_nth_trx_id(view, i)),
- (ulong) ut_dulint_get_low(read_view_get_nth_trx_id(view, i)));
- }
- }