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/******************************************************
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);
}
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