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/******************************************************
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;
ut_ad(mutex_own(&kernel_mutex));
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;
ut_ad(mutex_own(&kernel_mutex));
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 the 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 */
{
ut_ad(mutex_own(&kernel_mutex));
UT_LIST_REMOVE(view_list, trx_sys->view_list, view);
}
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