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/******************************************************
Cursor read
(c) 1997 Innobase Oy
Created 2/16/1997 Heikki Tuuri
*******************************************************/
#ifndef read0read_h
#define read0read_h
#include "univ.i"
#include "ut0byte.h"
#include "ut0lst.h"
#include "trx0trx.h"
#include "read0types.h"
/*************************************************************************
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 */
/*************************************************************************
Makes a copy of the oldest existing read view, or opens a new. The view
must be closed with ..._close. */
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 */
/*************************************************************************
Closes a read view. */
void
read_view_close(
/*============*/
read_view_t* view); /* in: read 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 */
/*************************************************************************
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 */
/*************************************************************************
Prints a read view to stderr. */
void
read_view_print(
/*============*/
read_view_t* view); /* in: read view */
/* Read view lists the trx ids of those transactions for which a consistent
read should not see the modifications to the database. */
struct read_view_struct{
ibool can_be_too_old; /* TRUE if the system has had to purge old
versions which this read view should be able
to access: the read view can bump into the
DB_MISSING_HISTORY error */
dulint low_limit_no; /* The view does not need to see the undo
logs for transactions whose transaction number
is strictly smaller (<) than this value: they
can be removed in purge if not needed by other
views */
dulint low_limit_id; /* The read should not see any transaction
with trx id >= this value */
dulint up_limit_id; /* The read should see all trx ids which
are strictly smaller (<) than this value */
ulint n_trx_ids; /* Number of cells in the trx_ids array */
dulint* trx_ids; /* Additional trx ids which the read should
not see: typically, these are the active
transactions at the time when the read is
serialized, except the reading transaction
itself; the trx ids in this array are in a
descending order */
trx_t* creator; /* Pointer to the creating transaction, or
NULL if used in purge */
UT_LIST_NODE_T(read_view_t) view_list;
/* List of read views in trx_sys */
};
#ifndef UNIV_NONINL
#include "read0read.ic"
#endif
#endif
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